A randomised, double-blind, sham-controlled study of left prefrontal cortex 15 Hz repetitive transcranial magnetic stimulation in cocaine consumption and craving.

BACKGROUND: Cocaine use disorder (CUD) is a global health issue with no effective treatment. Repetitive Transcranial Magnetic Stimulation (rTMS) is a recently proposed therapy for CUD.
METHODS: We conducted a single-center, randomised, sham-controlled, blinded, parallel-group research with patients randomly allocated to rTMS (15 Hz) or Sham group (1:1) using a computerised block randomisation process. We enrolled 62 of 81 CUD patients in two years. Patients were followed for eight weeks after receiving 15 15 Hz rTMS/sham sessions over the left dorsolateral prefrontal cortex (DLPFC) during the first three weeks of the study. We targeted the DLFPC following the 5 cm method. Cocaine lapses in twice a week urine tests were the primary outcome. The secondary outcomes were craving severity, cocaine use pattern, and psychometric assessments.
FINDINGS: We randomly allocated patients to either an active rTMS group (32 subjects) or a sham treatment group (30 subjects). Thirteen (42%) and twelve (43.3%) of the subjects in rTMS and sham groups, respectively, completed the full trial regimen, displaying a high dropout rate. Ten/30 (33%) of rTMS-treated patients tested negative for cocaine in urine, in contrast to 4/27 of placebo controls (p = 0.18, odd ratio 2.88, CI 0.9-10). The Kaplan-Meier survival curve did not state a significant change between the treated and sham groups in the time of cocaine urine negativisation (p = 0.20). However, the severity of cocaine-related cues mediated craving (VAS peak) was substantially decreased in the rTMS treated group (p<0.03) after treatment at T1, corresponding to the end of rTMS treatment. Furthermore, in the rTMS and sham groups, self-reported days of cocaine use decreased significantly (p<0.03). Finally, psychometric impulsivity parameters improved in rTMS-treated patients, while depression scales improved in both groups.
CONCLUSIONS: In CUD, rTMS could be a useful tool for lowering cocaine craving and consumption. TRIAL REGISTRATION: The study number on clinicalTrials.gov is NCT03607591.

Introduction

Repetitive transcranial magnetic stimulation (rTMS) of the left dorsolateral prefrontal cortex (DLPFC) could be a helpful additional approach to conventional treatment for cocaine use disorder (CUD) [1]. As the addiction persists, dopamine decreases with changes involving the brain’s prefrontal region, specifically the orbitofrontal cortex and the cingulate gyrus [2]. Thus, non-invasive brain stimulation techniques may alleviate some of the core symptoms of cocaine abuse [2,3]. rTMS directly impacts several functions altered by cocaine use, including reward, craving, cognitive control, and the influence of dopamine release [4]. However, in terms of clinical outcomes, these responses are diversified. The neurobiological bases of addiction focus on the dopaminergic and glutamatergic systems in modulating transmitter release, metabolism and synaptic function in what is referred as neural plasticity. CUD treatments rely on manipulating these circuits, as well as other inputs and inhibitory systems [4-6].

A rationale for CUD rTMS treatment has occurred in animal studies but with no consensus on humans’ correspondences so far [7]. At a low frequency (1 Hz), rTMS is typically inhibitory [8]. At high-frequency, rTMS (>5 Hz) acts as excitatory [9].

To ensure the efficacy of humans’ methodology, we need blinded, sham-controlled, prospective, and randomised trials. In the absence of any FDA/EMA-approved pharmacological treatment, international guidelines recommend psychosocial treatment as a first-line approach in CUD. However, it still fails to ensure a long-term response in the majority of patients [10]. A few trials have shown the efficacy of high-frequency rTMS treatment on CUD, but they were mostly open-label, not sham-controlled [1,11-13] and of low power [14].

Specific objectives or hypotheses

We conducted a randomised, monocentric, sham-controlled, double-blind, parallel-group RCT study, following the protocol previously published [15]. Our specific objectives were to confirm in humans the action of rTMS in reducing cocaine use, craving, depression, anhedonia, and impulsivity, comparing the results of a sham group to an active rTMS unselected typical CUD patients.

Methods

Trial design and any changes after trial commencement

The study was a parallel-group, randomised, active-controlled RCT trial with a 1:1 allocation ratio. The study involved the Toxicology Unit, the Neurophysiology Unit, and the Psychiatry Unit of Careggi University Hospital, Florence, Italy. We recruited participants among patients diagnosed with CUD according to DSM-V criteria, seeking CUD treatments and referred to our service either by the Emergency Department or by primary care physicians/Substance Abuse Services in the Florence metropolitan area, Italy. There were no changes after the trial commencement.

Participants, eligibility criteria, and settings

We assessed the outcomes twice a week and reported results graphically at three significant points: baseline (T0), post-treatment (T1), and eight weeks later (T2). The protocol was approved by the Azienda Ospedaliero-Universitaria Careggi Ethics Committee (CEAVC SPE. 16.309; MagneTox trial, Jul 17, 2017). Following the Helsinki Declaration, all patients signed an informed consent form after receiving the study description. The published method details the inclusion and exclusion criteria stages, rTMS application protocol, and outcomes [15].

The Ethics Committee prohibited the withdrawal of pre-existing pharmacological treatments and psychotherapy. Therefore, psychoactive drugs were either maintained unmodified if chronically administered or titrated/adjusted for steady-state achievement if recently prescribed before starting rTMS. We consequently continued psychotherapy.

Inclusion and exclusion criteria

The inclusion criteria were age 18–65 years, DSM-5 criteria for CUD, a positive cocaine test in urine, and written informed consent. In addition, a modified pharmacological treatment within 4 weeks, previous rTMS treatment, concomitant alcohol or drug use, a major psychiatric or neurological disorder, illiteracy or cognitive impairment, pregnancy or lactation were all exclusion criteria.

Procedures, randomisation, and masking

Between October 2017 and December 2019 (2 years), 81 consecutive patients sought treatment for CUD and were eligible, with 62 enrolling. For sex, age, length of CUD, the extent of cocaine use, the 19 patients considered at entry and lost at admission did not vary from the 62 enrolled. Therefore, we assigned patients to either an active rTMS group (32 subjects) or a sham treatment group (30 subjects).

Patient characteristics, basal and after randomisation, are presented in Tables 1 and 2. When two (or more) consecutive negative urine test results occurred at the latest observations, a patient was considered drug-free. The timing considered for the study is detailed in Scarpino [15]. In addition, we conducted craving and psychometric assessments as well as an urine test for cocaine use twice a week. To present the results, baseline (T0) marked the patients’ inception, while T1 marked the end of rTMS treatment (four weeks), and T2 indicated the end of follow-up after two months (total twelve weeks).

Table 1

Patient’s data at baseline.

	min	mean	max	SD	n
VAS base T0	0	4	10	3	36
VAS peak T0	0	8	10	3	57
CCQ T0	10	29	69	14	50
SDQ T0	68	122	198	31	57
SHPS T0	0	3	12	3	55
UPPS-neg T0	1.1	2.0	3.6	0.5	55
UPPS-prem T0	1.2	2.2	3.6	0.44	56
UPPS-pers T0	1.2	2.2	4.0	0.52	56
UPPS-ss T0	1.3	2.2	3.8	0.64	56
UPPS-pos T0	1.1	2.6	4.0	0.70	56
males n(%)	49 (83%)
CUD>10yrs	35(63%)
CUD>5yrs	4(18%)
CUD<5yrs	5(19%)
twice a week use	25(45%)
daily use	17(31%)
hourly use	6(11%)
weekly/monthly
use	7 (15%)
sniffing	38 (65%)
smoking	22 (38%)
ev use	8 (14%)

T0 = basal.

Table 2

Patients’ data after randomisation.

	sham					rTMS
	min	mean	max	SD	n	min	mean	max	SD	n
VAS base T0	0	4.5	10	3	30	0	3.4	8	3	27
VAS base T1	0	3	7	3	19	0	2	10	3	17
VAS base T2	0	2	8	3	11	0	3	9	3	12
VAS peak T0	2	9	10	3	27	0	8	10	3	30
VAS peak T1	0	7	10	4	17	0	6	10	4	17
VAS peak T2	0	6	10	5	11	0	7	10	3	10
CCQ T0	10	31	69	16	22	10	27	65	13	28
CCQ T1	0	21	39	13	15	10	22	60	16	17
CCQ T2	10	28	70	19	12	10	21	67	18	10
SDQ T0	80	125	188	30	27	68	120	198	32	30
SDQ T1	64	101	149	24	19	65	104	173	32	19
SDQ T2	79	110	184	33	15	68	97	173	30	11
SDQ T0	80	125	188	30	27	68	120	198	32	30
SDQ T1	64	101	149	24	19	65	104	173	32	19
SDQ T2	79	110	184	33	15	68	97	173	30	11
SHAPS T0	0	4	10	3	26	0	3	12	3	29
SHAPS T1	0	2	8	2	19	0	2	9	3	19
SHAPS T2	0	3	7	2	15	0	3	11	3	10
UPPS-neg T0	1.4	2.1	3.3	0.4	25	1.1	2.0	3.6	0.6	30
UPPS neg T1	1.2	2.1	3.3	0.61	19	1.10	2.43	3.8	.65	19
UPPS neg T2	1.20	2.37	3.80	.62	16	1.70	2.45	3.80	.63	12
UPPS-prem T0	1.20	2.23	3.30	.44	26	1.40	2.24	3.30	.45	30
UPPS-prem T1	1.00	2.12	2.80	.533	19	1.40	2.11	3.00	.47	19
UPPS-prem T2	1.00	2.06	2.90	.454	16	1.10	2.02	2.80	.62	12
UPPS-pers T0	1.50	2.28	3.30	.47	26	1.20	2.28	4.00	.57	30
UPPS-pers T1	1.20	2.02	3.00	.427	19	1.40	2.03	3.00	.47	19
UPPS-pers T2	1.60	2.15	2.90	.48	16	1.3	2.18	2.80	.41	12
UPPS-s s T0	1.30	2.3	3.80	.72	26	1.4	2.4	3.4	.56	30
UPPS-ss T1	1.30	2.42	3.60	.69	19	1.50	2.43	3.70	.592	19
UPPS-ss T2	1.10	2.53	4.00	.86	16	1.40	2.55	3.70	.570	12
UPPS-pos T0	1.20	2.60	3.70	.69	26	1.10	2.66	4.0	.721	30
UPPS-pos T1	1.00	2.56	3.80	.70	19	1.40	2.72	4.4	.80	19
UPPS-pos T2	1.10	2.53	4.00	.75	16	1.70	2.80	4.00	0.67	12

T0 = basal.

Sequence generation:

An external team member conducted the randomisation sequence generation using a block randomisation algorithm (1:1).

Blinding, allocation concealment and implementation

Throughout the study, patients, medical staff, and researchers were blinded to the randomisation. In contrast, neurophysiology technicians necessarily could not be blinded but were forbidden from informing other members, including other neurophysiology technicians, medical doctors, and any other person, of the patient allocation. The research was done in a double-blind fashion. There was no control of the fidelity of the blinding.

Interventions

We randomly assigned CUD patients to either rTMS (treatment group) or sham rTMS (15 sessions of 5 days of treatments and 2 days of rest over three weeks) (control group).

Transcranial magnetic stimulation

The target point of rTMS was the dorsolateral prefrontal cortex and we employed the 5 cm method. Patients received 15 sessions of high frequency (15 HZ) rTMS with a pulse intensity of 100% (individual threshold levels), 60 pulses per train, an intertrain pause of 15 sec, 40 stimulation trains, and a sum of 2,400 pulses in 13 min.

We used a standard figure-of-eight coil MagPro X100 stimulator (MagVenture, Denmark) and active (code MC-F-B65) and sham coils (MCF-P-B65).

Motor hand hotspot and left DLPFC targeting:

The theoretical distance between the cortical region being targeted and a reference scalp point established by TMS will be used to identify the target of cortical stimulation (function guided procedure) [16].

The reference point will be the left cortical motor region. The coil will be positioned over the assumed left motor cortex area, and motor evoked potentials (MEPs) collected using the contralateral (right) first dorsal interosseous (FDI) muscle by EMG will be used to determine the hand motor hotspot. The coil will then be adjusted until a position is found where a single-pulse TMS yields repeatable MEPs elicited at the lowest stimulation intensity. The left DLPFC will then be located 5 cm anterior and 2 cm lateral to the hand motor hotspot [17].

The TMS position will be marked on an elastic cap customized for each patient for subsequent rTMS sessions. The coil will be attached to an adjustable arm, and the landmarks on the cap will be checked several times during the rTMS sessions to verify that the coil is correctly positioned on different days. The methods for determining the position of the M1 area and the motor threshold will be repeated before each rTMS session. The intensity of the rTMS will be determined by mapping the FDI muscle response and getting the individual’s resting motor threshold (rMT), which indicates the membrane-related excitability of cortical axons.

The rMT will be determined by determining the lowest stimulator output intensity required to obtain 5 out of 10 MEPs greater than 50 V using the MEP technique [18].

We will use a pulse intensity of 100% of their rMT when delivering real rTMS. During the 15 rTMS treatment sessions, the rMT will be measured daily for each participant to ensure safety and efficacy.

The coil center placed at the left DLPFC was pointing 45° relative to the midsagittal line. The placebo coil had aspect and sound level identical to the active coil, but the magnetic field was reduced by 80%, although it had a similar cutaneous sensation.

Sample size: The goal was to enroll 60 cocaine-addicted patients over 18 months, which was the calculated sample size for the study’s projected power [15].

Primary outcome

The primary outcome was the time to urine negativisation. The criteria for negativity were two consecutive negative cocaine urine tests at the end of available observation

Secondary outcomes

The secondary outcomes were VAS, CCQ, and psychometric scales, which indicated craving or changes in psychometric parameters.

Craving assessment

In this work, we have chosen to use two different scales for craving measurement: the Visual Analog Scale (VAS) and the 10-item Cocaine Craving Questionnaire (CCQ-Brief). For VAS in the respondent’s current state, craving ratings are given on a scale of 0 (not at all) to 10 (extremely). VAS scale was applied to measure craving at basal levels (T0), T1, and T2 either under neutral conditions (VAS base) or cocaine use-related cues (VAS peak). During these three-time points, patient’s craving in normal daily activities (VAS base) and in cocaine use-related activities (VAS peak) was assessed. In order to distinguish VAS base versus VAS peak, we presented images and recall of cocaine experiences and paraphernalia, and a detailed interview was performed.

Cocaine Craving Questionnaire-Brief was used to assess current craving status ("here and now") at the baseline (T0), T1, and T2 evaluations and twice a week before every programmed urine drug screen test collection designed in the trial protocol for the whole duration of the study (12 weeks). CCQ-brief sums up the ten questions total points, and the final score correlates with craving severity at the moment of CCQ assessment [19]. CCQ is indeed similar to Vas Base, but does not explore the cocaine use related activity (VAS peak). Finally, to build up the swimmer plot analysis, self-reported data on cocaine use were registered at every visit during the study.

Psychometric scales (behavioural and attitudinal assessment)

The self-reported scales for the psychiatric evaluation included the Symptoms of Depression Questionnaire (SDQ) for depressive symptoms, the Snaith-Hamilton Pleasure Scale (SHAPS) for anhedonia, and the UPPS-P Impulsive Behaviour Scale.

The SDQ is a 44-item instrument with Likert-type answers; the total score is a sum of the items, with higher scores delineating more severe depressive symptoms. The Snaith-Hamilton Pleasure Scale (SHAPS) is a self-reported 14-item instrument assessing anhedonia’s presence. Scores ≥ 3 indicate a state of anhedonia.

The UPPS-P explores five different traits of impulsivity such as i) negative urgency (tendency to act rashly under extreme negative emotions, UPPS-P-neg), ii) lack of premeditation (tendency to act without thinking; UPPS-P-prem), iii) lack of perseverance (inability to remain focused on a task; UPPS-P-pers), iv) sensation seeking (tendency to seek out novel and thrilling experiences; UPPS-P-ss), and v) positive urgency (tendency to act rashly under extreme positive emotions; UPPS-P-pos). Scores of UPPS-P-neg, UPPS-P-ss, and UPPS-P-pos pointing to one outline a higher impulsivity level for these domains. UPPS-P-prem and UPPS-P-pers close to one, on the other hand, imply less severe psychopathology.

Statistical analysis

The Shapiro-Wilk test confirmed the non-normal distributions of VAS, CCQ, and psychiatric scales. The Wilcoxon paired test was then employed to test differences in continuous variables (VAS, CCQ, and psychiatric scales) with time. The Kaplan—Meier survival curves plotted the cumulative proportions of drug urine positive patients in the treated and sham groups with time, employing the Mantel-Cox log-rank test to assess the difference. A multivariate Cox model evaluated the influence of different patient characteristics on urine negativisation, with all variables entered with the Wald method. For the time points T1 and T2, the number of cases available at T1 was 41 patients (22 rTMS (70%) and 19 sham (68%)) and at T2 25 patients (13 rTMS (42%) and 12 sham (43%).

Trial status

The study was registered on ClinicalTrials.gov with identifier number NCT03607591. The Enrolment was from October 2017 to April 2020, when the codes were exposed for analysis. The main reason for the delayed registration of the study was the lack of awareness of this policy at the time of the start of the recruitment. We confirm that all ongoing and related trials for this intervention are registered.

Results

Participant flow and Baseline data

In two years, 81 patients seeking treatment for CUD were identified as potential study participants, with 62 enrolling (Fig 1 and Table 1). The 19 missed patients did not differ from the 62 enrolled in sex, age, CUD duration, cocaine use frequency, or assumption modalities. The 62 patients who participated in the study (Fig 1) had a mean age of 40,7±9 years; 51 males, 11 females. Patients were randomly assigned to either the active rTMS group (32 subjects) or the sham treatment group (30 subjects) (Fig 1 and Table 2).

Fig 1

Participant flow diagram.

Numbers and analysis for each outcome and subgroup analyses

One and two subjects prematurely disenrolled before receiving treatment in the rTMS AND SHAM group, respectively. Therefore, at the start of the study rTMS/SHAM sessions, 31 patients were treated with rTMS and 28 with sham. A high dropout was observed during the treatments both in rTMS (n = 18; 58%) and sham group (n = 16; 57%). The patients completing the study did not differ from those dropping for frequency and pattern of cocaine use, VAS base or CCQ, but differed for the number of treatments and peak VAS. Dropped outpatients showed an entry average VAS peak of 9.5 (SD 0.56), while patients continuing the study had an entry average VAS peak of 7 (SD 1.8), t-test p<0.006.

Since one patient in the rTMS group and one in the sham group neglected to release urine samples, the statistical analysis of urine drug tests was on 30 and 27 patients in the rTMS and sham group, respectively. When two consecutive drug negative urine tests were used as criteria for negativity at the end of the observations, 10/30 (33%) of the rTMS treated patients showed urine negativisation, compared to 4/27 (14%) of the sham controls (odd ratio 2.88, CI 0.9–10, p = 0.18). The log-rank test estimated the time to urine negativisation in survival analysis (Fig 2). Four patients entered the study with a negative urine test on the first day of rTMS treatment/sham and did not have another positive test for the study duration. The time to negativisation was listed as 0 for them (immediate). In the survival analysis, the average time to negativisation in the Mantel-Cox model were 90 days (CI 68 to 112 days) and 61 days (CI 40 to 83) in sham and rTMS group, respectively. The Mantel-cox log-rank test wax X2 = 1.57, p = 0.20. The results did not change in a best-case-worst-case scenario including or excluding the four left-censored patients. We estimated the effect of sex, VAS, CCQ, psychiatric scales, drug therapy, psychotherapy, and cocaine use frequency on urine negativisation using a Cox proportional hazard analysis. The model had a significant goodness of fit (p<0.01). and identified VAS peak (cocaine-related cue-induced VAS) at baseline T0 as the only variables associated with urine negativisation (p = 0.037, odd ratio 0.68, CI 0.68–0.98), meaning that higher VAS peak values correspond to a minor effect of sham/rTMS therapy, a higher probability of dropout, and a lower probability of urine negativisation. The swimmer plots graph presents the complete monitoring of the study (Fig 3). Each patient’s cocaine use history is colour-coded as red segments for days of self-reported use and green sections for days of self-reported abstinence and is shown in decreasing observation length. Panel A represents the sham subject, while Panel B represents the rTMS treatment group. Urine drug screen results were coded in red, orange, or green dots in each line for positive, borderline, and negative urine drug screens. Triangles marked the drug urine tests at T1 and T2 time points. The top blue bars show the time limits of rTMS or sham application. Self-reported days of cocaine use were 35% and 52% in the rTMS and sham groups, respectively. This percentage differed statistically between groups (Odds ratio for negativisation: 3.4, CI: 1.1 to 10, p<0.03).

Fig 2

Cumulative proportion of positive urine samples and numbers at risk in active rTMS and sham-treated group with time (days).

The Mantel-Cox test is p = 0.20. Tics indicate censored patients.

Fig 3

Patients’ histories are presented in decreasing length of observation and colour coded as red for the days of use or referred use and green for abstinence days.

Panel A represents the subject randomised to the sham treatment group, while panel B represents the active rTMS treatment. We marked each line’s urine drug screen results, codified as red, orange, or green dots for positive, borderline, and negative urine drug screens. Triangles marked the urine drug screen tests at T1 and T2 time points. The top blue bars indicate the application of rTMS or sham treatment.

At various points during the study, we examined the VAS scale (basal and peak, i.e., neutral cues and cocaine-related cues induced, respectively) and the CCQ, as mean and SD (Fig 4 and Table 2 for raw numbers at baseline (T0), T1, and T2). During the study, while VAS base craving measurement decreased in both treated and sham groups (Wilcoxon test p<0.05 for treated and p<0.02 sham), VAS peak craving showed a significant decrease in rTMS-treated but not sham-treated patients (p<0.03 T0 vs T1). Only the sham group experienced a significant decrease in CCQ (p<0.01 T0 vs. T1). Psychiatric evaluation for rTMS and sham group are presented in Fig 5. Compared to baseline, SDQ mean total score was significantly lower at T1 for both treated and sham group (p<0.003 T0 vs T1 and p<0.03 T0 vs T1, respectively). Conversely, the T0-T2 comparisons produced inconclusive results, even though the T1-T2 comparison resulted in a significant elevation of SDQ symptoms only in the sham group (Fig 5, Panel A). The SHAPS mean scores varied significantly in the sham group, with a reduction at T1 as compared to baseline (p<0.03 T0 vs T1). Among the UPPS-P subscales, a considerable amelioration was observed in the negative urgency subscale scores (UPPS-P neg) in the T0-T1 and the T0-T2 comparisons for the rTMS group (Fig 5, panel C, p<0.02 T0 vs T1; p<0.001 T0 vs T2). Conversely, no other differences were outlined by the longitudinal evaluation of other UPPS-P subscales in the rTMS group. Further, none of the UPPS-P subscales delineated conclusive and stable longitudinal variations in the sham group, except for a reduction in the perseverance subscale (UPPS-P pers) (Fig 5, panel D, p<0.02 T0 vs T1).

Fig 4

Craving scales.

VAS (basal and peak) and CCQ (mean and SD) in the rTMS treated and sham-treated groups at T0, T1, and T2. The Wilcoxon signed-rank test evaluated differences.

Fig 5

SDQ (panel A), SHAPS (panel B), UPPS-Pn (panel C), UPPS-P-pers (panel D) in the rTMS and sham-treated groups at T0, T1, and T2. Significant differences were calculated with the Wilcoxon signed-rank test.

Harms

Only a minor treatment-related adverse effect was observed in a single patient undergoing one sham treatment session and experienced mild and transient paraesthesia.

Discussion

Our study reports the improvements (self-reported use, VAS peak and UPPS-P-neg rTMS vs sham) in patients with CUD following rTMS treatment stimulating the left DLPFC. Moreover, although not statistically different, urine negativisation time was improved in the rTMS population. Interestingly, the self-reported cocaine use was statistically different between the rTMS and sham groups. These results are among the firsts conducted in a large cohort of patients with the sham-controlled procedure, with an adequate follow-up, and in an actual real clinical setting without a preliminary selection of patients, thus avoiding selection biases. A previously published paper described our study methodology [15]. We aimed to adopt a sham-controlled, double-blind design to control the expected placebo effect and fine-tune the different aspects of the rTMS effect in CUD abstinence and craving.

The neurological basis for rTMS’s disease-fighting effects is unknown. The state of the cortex, age, sex, genetics, neurotransmitter and receptor differences, connectivity of the stimulated region, and finally, the position of the coil relative to the target population and head geometry are all likely to play a role with the stimulation protocol.

RCT with sham control is the standard gold method for evaluating rTMS clinical efficacy in other disorders, such as depression [20]. Previous clinical research in double-blinded sham-controlled randomised studies have been published [21,22]. These older studies underlined either a late reduction (over three months following rTMS application) in cocaine intake measured in hair analysis [21] or cocaine versus money choice in the rTMS group [22]. However, both these studies showed either a limited number of recruited patients or lower rTMS frequency or did not perform any follow-up. A recent RCT study had similar characteristics to our study in stimulus frequency, size of stimulation (mostly 5 cm method) and intensity, with significant results in diminished self-reported cocaine use and craving. Similarly to our study, no difference in cocaine urine levels was observed [23].

On the other hand, all the remaining studies were not double-blinded, nor sham-controlled or randomised [1,11-13]. Interestingly, these studies have underlined the effectiveness of rTMS in craving control [1,11,12,14,24], and two studies which measured cocaine urinalysis showed a better outcome in the rTMS group [14,25]. Nonetheless, these older studies showed insufficient quality and lacked adequate power in rTMS enrolled patients and other limitations such as the sample size/treatment duration [11], missing controls, and low numbers of cases.

Our study missed the neuronavigation system, which has been described as potentially useful even if its superiority has not been definitively proven so far [20]. The standard anatomical method (5 cm method) employed in our study can be easily generalised. Its efficacy has been demonstrated in depression, in which rTMS is now considered a proven therapeutic intervention. Indeed, recent rTMS application guidelines indicate the F4/F3 sites at the 10–20 EEG System (the "Beam F3" algorithm) as possibly a more anatomically accurate non-navigated method for targeting the DLPFC in the major depression trials [20] but there is no definite proof [6].

As unexpected results, we registered a high dropout rate in randomised patients throughout the study in both arms, not infrequent in CUD studies [26]. Indeed, the original sample size calculation was determined to be 30 in each arm to provide 80% power, with a 2-sided significance level of α = 0.05, to detect a difference for clinical improvement, assuming a dropout rate of 20% of the patients. Unfortunately, the dropout rate in the real setting was higher (nearly 60%), which is probably one reason for the proposed primary outcome failure. Moreover, the urine sample collection is scarcely adequate in the proposed study design. Indeed, urine sample collections were extremely erratic throughout the study in both arms, which reduced the study power. However, it is interesting to notice that this is a common problem in studies involving substance use disorder population s, often bypassed by using statistical strategies to handle the missing data. For this reason, in outpatient settings, urine sample collections seem not to be a reliable biomarker for a clinical trial’s goals. A standardised, reliable biomarker investigating for cocaine consumption should be necessarily proposed in future studies.

There was no statistically significant difference in the time to urine negativisation between patients who received active rTMS and those who received a sham treatment in our trial. However, the survival curves did initially differentiate between the groups, and the average time to negativisation was shorter with the active therapy. The frequency of patients with urine negativisation was significantly higher in the same group, indicating an early effect of rTMS in this experimental setting and probably confirming the need for a subchronic rTMS treatment [25].

Positive results were found by using a swimmer plot analysis following an interview about daily cocaine use. We chose this type of analysis since it reflects a better picture of the cocaine pattern of use reported day by day, similarly to Madeo and co-workers [25]. Interestingly, the results are very comparable to the most recent RCT rTMS/CUD report [23], and both study confirm the same pattern of results.

Analysing the secondary outcomes revealed useful information on the specific effect on VAS, craving, depression, and impulsivity, which corresponded to symptoms release. CUD often clusters with impulsive behaviour and depression, with a complex interaction between these psychopathological areas [27,28]. Craving is a hallmark symptom of CUD [2,19]. VAS for cocaine craving assessment has been previously validated in CUD patients [29]. Previous studies demonstrated that rTMS to the left DLPFC was able to reduce VAS cue-induced craving in long-term heroin users [30] as well as in a case report of opioid and cocaine use disorder [31]. However, pre-post change analysis for VAS cocaine cue-induced craving was not performed due to time limitations for each visit [32]. Visual Analogue Scale was used to measure global craving for substances. Indeed, the association between the intensity of craving and substance use disorders severity is well established [27]. Therefore, high VAS at peak in CUD patients suggests that higher cocaine-related cues induced craving could be proposed as a negative prognostic factor for the success of CUD treatment in general and rTMS treatment. For this reason, we propose to differentiate craving measurement in basal and peak measurement.

The VAS scale application has already been proposed in pain [33], as well as in addiction research [11]. However, even the effect on VAS is not permanent and seems to fade shortly after the end of rTMS treatment. This is consistent with the recent introduction of rTMS protocols that implies the repetition of the rTMS sessions, reaching for the maintenance of the result on cocaine use in the long term [25].

As for depression, anhedonia, and impulsivity, both substance-induced and independent depressive symptoms can contribute to relapse into cocaine utilisation [34]. In this sense, monitoring these dimensions of psychiatric interest is of utmost clinical value, and an open-label study already suggested a potential effect of rTMS on cocaine users’ psychopathology [35,36]. SDQ scores showed similar results in the T0-T1 interval for both the rTMS and the sham group. This concurrent variation may partly be explained by a significant placebo effect, extensively acknowledged in rTMS treatments. Besides, rapid-onset and transient amelioration of depressive symptoms have already been described in treating mood disorders [27,28]. Conversely, even though T0-T2 comparisons led to inconclusive findings, a significant potential for the rTMS group could be tied to different T1-T2 trends. Indeed, a further, non-significant improvement of SDQ scores was observed in the rTMS group, whereas a loss of early progress was observed in the sham group. The presented data’s inconclusive effect is most likely due to the small sample size and high dropout rate. Nonetheless, the role of mood in subjects undergoing rTMS for substance use disorders warrants further investigation, as it had prognostic value in an RCT involving methamphetamine-dependent patients [37].

Concerning anhedonia, the present trial did not show relevant improvements of this psychopathological dimension, except for a single comparison in the sham group (pT0-T1 < 0.03). However, the significance of this finding is unclear since anhedonia is a trans-nosographic dimension [38].

A previous study showed an overall negligible effect of rTMS on impulsive behaviours [39], and the present trial generally confirmed this observation. More in detail, sensation seeking, lack of premeditation, and positive emotion management were globally stable across time. Regarding perseverance, a similar trend (although non-significant for the rTMS group) was observed for both the treated and the sham group, and it is probably to be ascribed to early improvements and behavioural consequences of the above-mentioned placebo effect. On the contrary, significant variations were observed for the treated group negative urgency scores with clinically and theoretically sound explanations [40]. Thus, negative emotional affect, which was represented in the overall sample (as proved by the depression and anhedonia baseline scores), is the main drive of cocaine use. In this sense, it can be speculated that positive toxicological outcomes are indirectly tied to improvements in this specific sub-domain, rather than compulsive and sensation-seeking behaviour.

Finally, this study and the recent RCT by Garza-Villareal and coworkers had similar clinical and rTMS parameters, both as frequency of stimulation (5 Hz versus 10Hz), and number, intensity, and site of stimulations (mostly 5cm method) [23]. The similar results support the external validity of the findings.

Limitations and generalizability

This study has limitations that may have hampered its effectiveness. First, the high dropout rate underpowered the results. Furthermore, a longer rTMS treatment duration, as well as an extended follow-up period, may allow for the detection of longer-term differences. The randomisation protocol and the rigorous analysis, which was limited to pre-specified criteria, eliminated potential bias sources reinforcing the results.

Conclusion

Our final interpretation should weigh the benefits against the risks, with the therapy being well tolerated and free of side effects. Considering all the evidence obtained in the study, such as the effect on self-reported use, depression, VAS at peak, and impulsivity, rTMS could be considered beneficial and safe add-on therapy in CUD.

(DOC)

Click here for additional data file.

Transfer Alert

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26 Jul 2021

PONE-D-21-19751

A randomized, double-blind, sham-controlled study of left prefrontal cortex 15 Hz repetitive transcranial magnetic stimulation in cocaine consumption and craving.

PLOS ONE

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Reviewer #3: Yes

**********

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Reviewer #1: No

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Reviewer #3: Yes

**********

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Reviewer #1: The objective of this single-center, parallel group, randomized (sham) controlled trial (RCT) is to assess the effectiveness rTMS therapy for treating cocaine use disorder (CUD). The study was registered as a RCT within the clinicaltrials.gov registry (with a legit NCT number), and was approved by the respective IRB/Ethics Committee. While the study objectives sound interesting, is important, and on target, a number of shortcomings were observed, in regards to abiding by the CONSORT guidelines for conducting and reporting results of high-quality randomized controlled trials (RCTs). Some other (statistical) comments were also added.

1. Methods:

Methods reporting require an orderly manner following CONSORT guidelines, without repeating information, such as Trial Design, Participant Eligibility criteria and settings, Interventions, Outcomes, sample size/power considerations, Interim analysis and stopping rules. Randomization (details on random number generation, allocation concealment, implementation), and Blinding considerations should be mentioned explicitly. The authors are advised to create separate subsections for each of the possible topics (whichever necessary), and that way produce a very clear writeup. I see the Authors already made a sincere attempt; however, they are advised to write it carefully, following nice examples in the manuscript below:

https://www.sciencedirect.com/science/article/pii/S0889540619300010

Specific comments below:

(a) For instance, the randomization and allocation concealment should be made very clear (they are NOT the same thing); the trial staff recruiting patients should NOT have the randomization list. Randomization should be prepared by the trial statistician, and he/she would not participate in the recruiting.

(b) Sample size/power: There is no sample size/power paragraph presented; it is also not clear whether sample size determinations were done using the primary outcome variable (time to urine negativization). Also, sample size calculations should consider the desired effect size under consideration.

(c) Statistical Analysis:

(i) For the survival analytic endpoint, how is the (right) censoring determined? Is it administrative censoring, or something else?

(ii) Fig 2 is not really a Kaplan-Meier plot; one needs to plot the survival curves for urine negativization corresponding to the "sham" and "active" groups, and then conduct a log-rank test to produce the desired p-value.

(iii) The fit of the multivariate Cox model should be accompanied by necessary goodness-of-fit assessments, and checking the proportional hazards assumptions, through popular tests.

2. Results:

(a) The authors should check that any statement of significance should be followed by a p-value in the entire Results section. Otherwise, the Results section look adequate followed by a detailed discussion.

Reviewer #2: The paper by Lolli et al describes the effect of rTMS treatment on cocaine treatment-seeking cocaine addicts. The paper is well written and well designed representing yet another experimental effort that ultimately supports the use of rTMS in the treatment of cocaine addiction. Analysis of experimental data is now more accurate than a previous version of the paper I had seen elsewhere.

I would simply encourage the authors to comment on the possible neurobiological basis for TMS effects.

As such the discussion is merely clinical and reflections/ideas about the the neurobiology underlying clinical effects would help in reducing the 'exoteric aura' around TMS.

Reviewer #3: Lolli and colleagues report on a single site, randomized, double-blind, parallel-group, randomized controlled trial of high frequency rTMS vs. sham for cocaine use disorder. They describe strengths in their trial design and large sample size, however note their challenges with retention of participants as drop-out rates were high (equally in both groups). They did not find any significant differences in their primary outcome of urine toxicology, however a number of important secondary measures did show superiority of rTMS, including outcomes related to self reported use, depression, certain indices of craving, and impulsivity. Importantly, they note that rTMS was well tolerated without any significant adverse effects.

Given the growing interest in neuromodulation for addictive disorders, this study is a welcome addition to the literature. The authors are correct in stating that the vast majority of currently published studies are far too small and under-powered in nature to be confident about clinically significant therapeutic benefit. Given the unique and substantial risks in managing severe substance using populations, it also needs to be demonstrated in clinical trials that these treatments that require intensive follow up (e.g. daily treatment visits required of rTMS) can be feasible in those that abuse substances. This may be particularly challenging for very destabilizing substances such as cocaine. This manuscript provides data to address these current shortcomings in the literature well.

The main significant criticism is that this manuscript fails to address is the issue of rTMS targeting, which has become a field of intense debate and study. Current approaches typically include MRI based anatomical targeting, fMRI-based connectivity targeting, or other brain biomarkers (e.g. EEG). The rationale and excitement for neuromodulation in the addictions field is the ability to more specifically target aberrant neurocircuitry. Thus, the current paper’s target of “PMC/DLPFC” is very imprecise according to current standards. The PMC and DLPFC are relatively disparate regions of the cortex. Standard rTMS procedures, even those using only scalp-based measurements, aim to target only the DLPFC. One such method is the “Beam F3 method” which the uses the 10-20 EEG placement system is likely more precise. The authors do cite the Beam F4 method in their discussion, stating it is the most anatomically accurate non-MRI navigated method, but do not seem to use it themselves.

Other comments I have are relatively minor, but there are many of them, mostly related to increasing clarity of the writing of the manuscript. It will be important for the authors to address issues like blinding and statistical analyses to account for missing data, as these relate to the methodological issues that are important to the paper.

Introduction

- Line 61-62 is too definitive of a statement for such preliminary research cited.

- Life 65 don’t recommend wording of “restoring symptoms”, should be treating or alleviating symptoms

- Line 66-67 needs citations.

Methods

- Please consider reporting your protocol according to the CONSORT checklist of information to include when reporting a randomised trial.

- For clarity, I would suggest listing inclusion criteria and exclusion criteria separately

- For clarify, I would recommend using a different word than biweekly. It is a little bit unclear since this word can mean every 2 weeks or it can mean twice a week.

- Line 119: suggest using terminology, thus T0 should be “baseline” as previously described in the page before.

- Line 123: What does a “neurophysiology technician” refer to?

- Blinding was reported for participants and medical operators. Please comment on blinding by the raters for standardized scales. Was blinding successful and were any measures conducted to assess for fidelity of blinding? As mentioned above, it is not clear who the “neurophysiology technicians” are, but it is mentioned that they were not blinded – does this affect the integrity of the results in any way?

- I recommend using standard terminology for describing the motor threshold method. It is described in a confusing way, with it first referenced as an “individual threshold level” on line 126, then there is some vague description of MEPs around line 134-135 (is this using EMG? Was this resting motor threshold? Then it is mentioned again later in line 141-142 where this is more of a discussion based point about what the motor threshold represents. This can all be consolidated into a few lines or a paragraph all together.

- Please explain the rationale for targeting of the premotor cortex. It was not mentioned in the introduction or the beginning of the methods and was named for the first time on line 129 with just the acronym.

- The description of the target site and landmarking is difficult to follow. Line 132 to 134 seem to suggest there is landmarking done, but it is not clear what these landmarks are, when later it seems to suggest the landmarking is just based on uniform measurements (regardless of individual head shape and size). Where does this landmarking protocol come from? Has it been standardized or referenced before?

- It is not clear why the stimulation sits is “PMC/DLPFC”. These are relatively different sites on the cortex, and it is rather imprecise to lump these together. Furthermore, in the Abstract, the target site is only described as “DLPFC” alone.

- Line 154-156 is better reserved for an introduction or discussion section.

- The VAS protocol needs to be better described. It is not clear how the “VAS base” and “cocaine use-related activities” was actually conducted. Those descriptions provided (e.g. “meeting people who consume the drug”) do not explain whether these are imagined, or whether they are based on image or video cues as is standard in this field. I understand that the citations provided may better describe it, but a brief version of the steps should be available within the paper.

- For the Cocaine Craving Questionnaire, it is not clear how this “here and now” assessment is any different than the VAS. The VAS as currently described also sounds like it is a current craving assessment.

- For the self reported data on cocaine use, was there any specific method used? For example the Timeline Follow Back Method? Was quantity of use collected?

- Line 171 – the word “relevant” symptoms meant to say more severe total burden of symptoms? Does the scale differentiate between different types of symptoms in terms of importance and how would this be described in a total score?

- Please reword line 180-181, it is too difficult to understand in this form

- Statistical analysis: please describe how missing data was accounted for, particularly as your primary outcome is negativity at the end of available observation, may have biased the results towards an effect by missing participants that dropped out due to relapse.

Results:

- For the differences stated between the drop outs and those that continued the study, are those measures listed in line 207-208 referring to baseline cocaine use or throughout the study?

- Were the drop out percentages listed referring to drop out before T1 or T2? Did this affect the analysis?

Discussion:

- Beam F3 may have been more accurate but this is not the way the authors did it in this study

- The discussion of dropouts and difficulty obtaining urine samples is a very interesting paragraph. The authors propose alternate biomarkers of cocaine consumption. However, would an alternate biomarker have any influence on the drop out rate?How much is the drop out rate related to the issues with urine collection? In other words, is it a significant problem that participants that do not drop out yet still a urine sample cannot be obtained?

- The authors discuss using a daily interview and the swimmer’s plot as a good way of identifying daily use. Is there a reason why the Timeline Followback Method was not used? The authors cite Garza-Villarreal et al (2021) who did indeed use the TLFB.

- In describing the strengths of this study as being large and a blinded RCT, the authors do not credit other such studies including Garza-Villarreal et al. (2021), who similarly present a rigorous study design. It may be interesting to include a brief comparison with this study in the discussion section. Similarly, there are other large, well designed RCTs published in methamphetamine use disorder, which although is not exactly the same as CUD, has obvious overlap. It may be interesting to have some discussion of these studies as well in relation to this manuscript.

**********

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Reviewer #2: Yes: Marco Diana

Reviewer #3: No

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29 Sep 2021

Firenze 29-09-2021

Response to the Editor and referees of our article PONE-D-21-19751 "A randomised, double-blind, sham-controlled study of left prefrontal cortex 15 Hz repetitive transcranial magnetic stimulation in cocaine consumption and craving."

Dear Editor of Plos one,

Thank you for the decision letter dated July 26, 2021, and the reviewers' comments to improve the paper. The manuscript has been revised in response to the reviewers' suggestions and editorial guidelines. Please find a point-by-point response to the journal requirements and the Reviewers' comments in our resubmission.

We hope that the revised version of the paper will now meet the publication criteria of PLOS ONE.

Sincerely,

Francesco Lolli, MD, Ph.D.

Comments for the Editor

A rebuttal letter (this file) is included below and named 'Response to reviewers'. A revised 'Manuscript with Track Changes' is included as well as an unmarked clean copy 'Manuscript.'

Our updated financial statement in the cover letter is

"“Azienda Ospedaliera Universitaria Careggi, Firenze, Italy; Fondazione Cassa di Risparmio Firenze, Italy”

We employed the guidelines and software recommended for checking figures.

Our study protocol was preliminarily published in Scarpino et al. 2019.

Our manuscript meets the 'PLOS ONE's style requirements, including those for file naming.

We endorse the immediate and preliminary study registration. Unfortunately, we experienced a delay in the study registration, now detailed in the text.

As per the journal's editorial policy, we included in the Methods section of our paper:

1) After checking recent literature (M Al-Durra, BMJ 2020; 369:m982[Prospective registration and reporting of trial number in randomised clinical trials: global cross-sectional study of the adoption of ICMJE and Declaration of Helsinki recommendations]), a phrase was added in the methods section as requested ("The main reason for delayed registration was lack of awareness of this policy at the time of starting recruiting").

2) We confirmed that all related trials are registered by stating: "The authors confirm that all ongoing and related trials for this intervention are registered".

3) the 'Funding Information' and 'Financial Disclosure' sections do now match.

Our amended financial statement is “Azienda Ospedaliera Universitaria Careggi, Firenze, Italy; Fondazione Cassa di Risparmio Firenze, Italy”.

Furthermore, we corrected it in the online system.

5.

The data availability statement is now introduced as: “Data cannot be shared publicly because contain sensible information. The data will be available to investigators whose independent review committee has approved the proposed use for meta-analysis.”

6. we refer to Figure 4 in the text.

7. there is no supporting/supplementary information

Comment to reviewer#1

Original comment:"The objective of this single-centre, parallel-group, randomised (sham) controlled trial (RCT) is to assess the effectiveness rTMS therapy for treating cocaine use disorder (CUD). The study was registered as an RCT within the clinicaltrials.gov registry (with a legit NCT number), and was approved by the respective IRB/Ethics Committee. While the study objectives sound interesting, is important, and on target, a number of shortcomings were observed, in regards to abiding by the CONSORT guidelines for conducting and reporting results of high-quality randomised controlled trials (RCTs).

Methods reporting require an orderly manner following CONSORT guidelines, without repeating information, such as Trial Design, Participant Eligibility criteria and settings, Interventions, Outcomes, sample size/power considerations, Interim analysis and stopping rules. Randomisation (details on random number generation, allocation concealment, implementation), and Blinding considerations should be mentioned explicitly. The authors are advised to create separate subsections for each of the possible topics (whichever necessary), and that way produce a very clear writeup. I see the Authors already made a sincere attempt; however, they are advised to write it carefully, following nice examples in the manuscript below: (Erbe et al 2019)"

After our efforts to comply with space limitations, the reviewer rightly reports shortcomings in abiding by the CONSORT guidelines for conducting and reporting results of high-quality randomised controlled trials (RCTs). As suggested, we now applied stringently the guidelines such as Trial Design, Participant Eligibility criteria and settings, Interventions, Outcomes, sample size/power considerations, Randomisation (details on random number generation, allocation concealment, implementation), and Blinding considerations. In addition, we used subsections and the format signalled in Erbe et al. 2019, as suggested.

________

Original comment:""(a) For instance, the randomisation and allocation concealment should be made very clear (they are NOT the same thing); the trial staff recruiting patients should NOT have the randomisation list. Randomisation should be prepared by the trial statistician, and he/she would not participate in the recruiting.

(b) Sample size/power: There is no sample size/power paragraph presented; it is also not clear whether sample size determinations were done using the primary outcome variable (time to urine negativisation). Also, sample size calculations should consider the desired effect size under consideration.

c) Statistical Analysis"

i) For the survival analytic endpoint, how is the (right) censoring determined? Is it administrative censoring, or something else?

(ii) Fig 2 is not really a Kaplan-Meier plot; one needs to plot the survival curves for urine negativisation corresponding to the "sham" and "active" groups, and then conduct a log-rank test to produce the desired p-value.

(iii) The fit of the multivariate Cox model should be accompanied by necessary goodness-of-fit assessments, and checking the proportional hazards assumptions, through popular tests.

(a) The randomisation and allocation concealment and blinding were specified in the appropriate sections

(b) The sample size calculation was described in the method paper by Scarpino et al. (2019). They are also added in the present study as suggested

(c)

i. It is an administrative censoring. All subjects complete the course of the study and are known to have experienced either of the two outcomes at the end of the study

ii. We corrected fig.2 to a typical Kaplan-Meyer plot as suggested

iii. The goodness of fit and p values of model are now reported as suggested

________________________

Original comment:"The authors should check that any statement of significance should be followed by a p-value in the entire Results section

(a) in the results section, any statement of significance is now followed by a p-value

____________________

Reviewer#2

Original comment:""I would simply encourage the authors to comment on the possible neurobiological basis for TMS effects".

We thank the reviewer for the suggestion. We considered better the neurobiological bases for rTMS effect, now presented in the introduction and discussed in relation to our results

__________________________

Reviewer#3

"

Original comment:"The main significant criticism is that this manuscript fails to address is the issue of rTMS targeting, which has become a field of intense debate and study. Current approaches typically include MRI based anatomical targeting, fMRI-based connectivity targeting, or other brain biomarkers (e.g. EEG). The rationale and excitement for neuromodulation in the addictions field is the ability to more specifically target aberrant neurocircuitry. Thus, the current paper's target of "PMC/DLPFC" is very imprecise according to current standards. The PMC and DLPFC are relatively disparate regions of the cortex. Standard rTMS procedures, even those using only scalp-based measurements, aim to target only the DLPFC. One such method is the "Beam F3 method" which the uses the 10-20 EEG placement system is likely more precise.

We do agree with the referee that rTMS targeting has become a hot topic for discussion and research. We are aware of the numerous possible targets. Our idea was to conform to the most popular target, and the name "PMC/DLPFC" came from a discussion with an international referee in our previous pubblication (Scarpino et al, 2019). At the time of protocol design, the beam F3 methods were not preferred. We now simplifyed the target name as simply DLPFC as in the main literature and following referee suggestion.

_______________________

Original comment:"Introduction

- Line 61-62 is too definitive of a statement for such preliminary research cited.

- Life 65 don't recommend wording of "restoring symptoms", should be treating or alleviating symptoms

- Line 66-67 needs citations.

Line 61-62 was changed accordingly

Life 65 now read "alleviating symptoms."

Line 66-67 have a new citation

__________________________

Methods

Original comment:"- Please consider reporting your protocol according to the CONSORT checklist of information to include when reporting a randomised trial.

- For clarity, I would suggest listing inclusion criteria and exclusion criteria separately

- For clarify, I would recommend using a different word than biweekly. It is a little bit unclear since this word can mean every 2 weeks or it can mean twice a week.

- Line 119: suggest using terminology, thus T0 should be "baseline" as previously described in the page before.

- Line 123: What does a "neurophysiology technician" refer to?

- Blinding was reported for participants and medical operators. Please comment on blinding by the raters for standardised scales. Was blinding successful and were any measures conducted to assess for fidelity of blinding? As mentioned above, it is not clear who the neurophysiology technicians" are, but it is mentioned that they were not blinded – does this affect the integrity of the results in any way?

We employed the CONSORT checklist for reporting a randomised trial according to this comment and those from reviewer#1.

Inclusion and exclusion criteria were listed separately

Biweekly was written twice a week.

Line 119 T0 was corrected to "baseline (T0)"

In line 123, please refer to https://college.mayo.edu/academics/health-sciences-education/clinical-neurophysiology-technology-program-minnesota/

Blinding. We now discuss the blinding for all personell. There was no control for the fidelity of the blinding. The neurophysiology technician has no contact with the raters, doctors, other patients, or other technicians, and it is now stated. At the time of starting of the study, there was no possibility to blind the technician to the two different coils. Nonetheless, we believe this has no bearing on the outcome of the study.

___________________

Original comment:"I recommend using standard terminology for describing the motor threshold method. It is described in a confusing way, with it first referenced as an "individual threshold level" on line 126, then there is some vague description of MEPs around line 134-135 (is this using EMG? Was this resting motor threshold? Then it is mentioned again later in line 141-142 where this is more of a discussion based point about what the motor threshold represents. This can all be consolidated into a few lines or a paragraph all together.

- Please explain the rationale for targeting of the premotor cortex. It was not mentioned in the introduction or the beginning of the methods and was named for the first time on line 129 with just the acronym.

- The description of the target site and landmarking is difficult to follow. Line 132 to 134 seem to suggest there is landmarking done, but it is not clear what these landmarks are, when later it seems to suggest the landmarking is just based on uniform measurements (regardless of individual head shape and size). Where does this landmarking protocol come from? Has it been standardised or referenced before?

- It is not clear why the stimulation sits is "PMC/DLPFC". These are relatively different sites on the cortex, and it is rather imprecise to lump these together. Furthermore, in the Abstract, the target site is only described as "DLPFC" alone.

- Line 154-156 is better reserved for an introduction or discussion section.

We now used standard terminology for describing the motor threshold method, and the whole procedure is described in a new paragraph.

The targeting of the premotor cortex is now described at the beginning of the methods and named.

The description of the target site and landmarking is new. We detailed the protocol and how it was done and standardised, and referenced

The "PMC/DLPFC" is now identified at the beginning of the methods as DLPFC through the paper. Therefore, the target site in the abstract conforms to this name.

Line 154-156 is now part of the discussion.

____________________________________________

Original comment:"The VAS protocol needs to be better described. It is not clear how the "VAS base" and "cocaine use-related activities" was actually conducted. Those descriptions provided (e.g. "meeting people who consume the drug") do not explain whether these are imagined, or whether they are based on image or video cues as is standard in this field. I understand that the citations provided may better describe it, but a brief version of the steps should be available within the paper.

- For the Cocaine Craving Questionnaire, it is not clear how this "here and now" assessment is any different than the VAS. The VAS as currently described also sounds like it is a current craving assessment.

- For the self reported data on cocaine use, was there any specific method used? For example the Timeline Follow Back Method? Was quantity of use collected?

The methods “VAS base" and "cocaine use-related activities" were better described, along with what was done, as suggested.

The distinctions between the Cocaine Craving Questionnaire and the VAS were clarified. CCQ is indeed similar to VAS Base, but does not explore the cocaine use related activity (VAS peak).

For the self-reported data, there was a quantity of use collected defined as single day of use. We did not employ any more specific method, since the TMB was not of general use at the time of the beginning of the study.

_________________

Original comment:"Line 171 – the word "relevant" symptoms meant to say more severe total burden of symptoms? Does the scale differentiate between different types of symptoms in terms of importance and how would this be described in a total score?

- Please reword line 180-181, it is too difficult to understand in this form

- Statistical analysis: please describe how missing data was accounted for, particularly as your primary outcome is negativity at the end of available observation, may have biased the results towards an effect by missing participants that dropped out due to relapse.

Line 171, it is “more severe symptoms”. The scale is a score composite with more item. The total score we employed is a a global evaluation

Line 180-181 was rewritten

- Statistical analysis: after the randomisation procedure, the number of missing values are balanced between the group. See the number of exposed in the Kaplan-Meyer plot

________________________

Original comment:"For the differences stated between the drop outs and those that continued the study, are those measures listed in line 207-208 referring to baseline cocaine use or throughout the study?

- Were the drop out percentages listed referring to drop out before T1 or T2? Did this affect the analysis?

We are refering to basal cocaine use.

The differences stated between the dropouts and those that continued the complete study in lines 207-208 refer to baseline cocaine use, with the idea of a possible future stratification of cases at entry.

The drop out percentages listed refer to observed at any time before termination of the study, they are listed in table 2 and text (numbers in results). Thus, drop out are distributed all along with the investigation.

__________________________

Original comment:"Beam F3 may have been more accurate but this is not the way the authors did it in this study

- The discussion of dropouts and difficulty obtaining urine samples is a very interesting paragraph. The authors propose alternate biomarkers of cocaine consumption. However, would an alternate biomarker have any influence on the drop out rate?How much is the drop out rate related to the issues with urine collection? In other words, is it a significant problem that participants that do not drop out yet still a urine sample cannot be obtained?

- The authors discuss using a daily interview and the swimmer's plot as a good way of identifying daily use. Is there a reason why the Timeline Followback Method was not used? The authors cite Garza-Villarreal et al (2021) who did indeed use the TLFB.

- In describing the strengths of this study as being large and a blinded RCT, the authors do not credit other such studies including Garza-Villarreal et al. (2021), who similarly present a rigorous study design. It may be interesting to include a brief comparison with this study in the discussion section. Similarly, there are other large, well designed RCTs published in methamphetamine use disorder, which although is not exactly the same as CUD, has obvious overlap. It may be interesting to have some discussion of these studies as well in relation to this manuscript.

Beam F3 method could have improved the results, but we employed a more commonly used target.

Comment on dropouts and difficulty obtaining urine samples. The dropout from the study end the urine collection in all patients. The randomization balance the drop out between the 2 arms In order to discuss the importance of new biomarkers we do believe they cannot influence the drop-out rate. Regarding the explanation on how the patients in tretment still have diffculties in urine sample collection, unfortunately we do non have any explanation. Indee it is well know that CUD and substance use disorders populations, is a very difficult population to study. We pointed ou these difficulties in the discussion section. (Pani et al. 2011)

We are discussing the Beam F3 method in the setting of our study and others, the role of dropouts, TLFB analysis versus the swimmer plot.

The swimmer plot is the method of reference to display individual patients results. As mentioned to the previous referee for craving, we did not employ any more specific method, since TLFB was not of general use at the time of the beginning of the study.

Finally, we discuss the critical points raised and identified by Garza-Villarreal et al. (2021) versus our results.

We recognise the relevance of the study from Garza-Villareal (2021), whis is now confronted, described and compared to our study in the discussion. We believe that the result, very simiilar, reinforce the conclusions.

The methamphetamine use disorder are cited.

______________________________

Sincerely

Prof. Francesco Lolli, MD, PhD

Università di Firenze, Italy

Francesco.lolli@unifi.it

Submitted filename: responsetoreviewers.docx

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28 Oct 2021

A randomized, double-blind, sham-controlled study of left prefrontal cortex 15 Hz repetitive transcranial magnetic stimulation in cocaine consumption and craving.

PONE-D-21-19751R1

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5 Nov 2021

PONE-D-21-19751R1

A randomised, double-blind, sham-controlled study of left prefrontal cortex 15 Hz repetitive transcranial magnetic stimulation in cocaine consumption and craving.

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