Clinically useful tumor fluorescence greater than 24 hours after 5-aminolevulinic acid administration.

Background: 5-aminolevulinic acid (5-ALA) is a valuable surgical adjuvant used for the resection of glioblastoma multiforme (GBM). Since Food and Drug Administration approval in 2017, 5-ALA has been used in over 37,000 cases. The current recommendation for peak efficacy and intraoperative fluorescence is within 4 h after administration. This narrow time window imposes a perioperative time constraint which may complicate or preclude the use of 5-ALA in GBM surgery. Case Description: This case report describes the prolonged activity of 5-ALA in a 66-year-old patient with a newly diagnosed GBM lesion within the left supramarginal gyrus. An awake craniotomy with language and sensorimotor mapping was planned along with 5-ALA fluorescence guidance. Shortly, after receiving the preoperative 5-ALA dose, the patient developed a fever. Surgery was postponed for an infectious disease workup which proved negative. The patient was taken to surgery the following day, 36 h after 5-ALA administration. Despite the delay, intraoperative fluorescence within the tumor remained and was sufficient to guide resection. Postoperative imaging confirmed a gross total resection of the tumor.
Conclusion: The use of 5-ALA as an intraoperative adjuvant may still be effective for patients beyond the recommended 4-h window after initial administration. Reconsideration of current use of 5-ALA is warranted. Copyright:

INTRODUCTION

High-grade gliomas (HGG) represent the most common primary intracranial tumor with an estimated 13,000–17,000 newly diagnosed cases each year.[17,20,21,29] Despite modest survival benefit with adjuvant therapies such as chemo-radiation and tumor-treatment fields, long-term prognosis with HGG is invariably discouraging with 1- and 2-year survival rates of 38% and 16%, respectively.[3] The preponderance of evidence suggests that the extent of resection (EOR) correlates strongly with survival. The use of advanced surgical adjuncts, such as intraoperative magnetic resonance imaging (MRI), and fluorescence-guided surgery (FGS), has shown promising results. Numerous RCTs have demonstrated that both tools increase EOR with an associated increase in progression-free survival.[18,22,24]

Since the US Food and Drug Administration’s approval of 5-aminolevulinic acid (5-ALA) in February 2017, over 37,000 patients with glioblastoma multiforme (GBM) have been operated on with the aid of FGS. The current recommended dose of 5-ALA is 20 mg/kg body-weight, administered orally 2–4 h before induction of anesthesia.[15] These recommendations arise from preclinical animal studies[23] and Phase I and 2 dose-escalation trials,[4,15,16] with additional support from a randomized, prospective, and double-blind study of alternative dosage regimens for HGG resection.[25]

5-ALA is a prodrug with selective intracellular conversion to protoporphyrin IX, the fluorescent downstream metabolite of 5-ALA that preferentially accumulates in high-grade tumor cells to glow under blue-light illumination.[8,12,16,23] In vivo animal studies report peak fluorescence between 1.5 and 4 h after administration,[19,23] yet, clinical experience has demonstrated visually discernible tumor fluorescence even 12–16 h after initial dosing.[7,13,28] While those instances of prolonged fluorescence have been informally described, we present the first reported case of clinically useful intraoperative tumor fluorescence >24 h after 5-ALA administration, without redosing.

CLINICAL PRESENTATION

A 66-year-old right-handed male initially presented with mild cognitive difficulty, dysphasia and progressive difficulty walking. On examination, a subtle neglect, acalculia, extinction to double simultaneous stimuli, and right-sided apraxia were noted. Evaluation with MRI demonstrated a partially cystic contrast-enhancing mass in the dominant supramarginal gyrus with fluid-attenuated inversion recovery positive signal intensity extending above to the superior parietal lobule, suggestive of glioma [Figure 1]. An electroencephalogram showed cortical irritability on the left but no definite seizures. His symptoms improved with levetiracetam and dexamethasone, which he continued until surgery. Given the eloquent location of his tumor, the surgical plan included an awake language and sensorimotor mapping using phase reversal and cortical and subcortical motor-evoked potentials to preserve function. We also elected to make use of 5-ALA and intraoperative MRI to maximize resection.

Figure 1:

Preoperative magnetic resonance imaging (MRI) of the brain with and without contrast demonstrating contrast-enhancing left parietal cystic lesion. (a) Axial MRI T1-weighted, (b) axial T1-weighted with gadolinium, (c) sagittal T1-weighted with gadolinium, and (d) coronal T1-weighted with gadolinium.

On arrival to the preoperative area, a 20 mg/kg oral dose of 5-ALA was given at 5:50 AM, within 2 h of surgery. Before transport to the operative suite, the patient developed a fever of 38.8°C, which increased to 39.4°C on repeat evaluation. After consultation with our clinical trials team and anesthesia, surgery was deferred in favor of further evaluation of the cause of the fever. He was transferred to the intensive care unit and kept under light precautions in the interim. His fever was self-limiting. Further evaluation revealed no infectious etiology. Surgery was rescheduled for the following morning at 9:30 AM, more than 24 h after administration of 5-ALA.

During surgery, cortical mapping demonstrated several areas critical for language function. The non-enhancing lesion was found to be in an area that, when stimulated, resulted in movement of the opposite arm and face as well as dysesthetic pain in a similar distribution. After cortical mapping and partial white light resection, the first utilization of fluorescence came a full 32 h after 5-ALA administration [Figure 2]. The cystic enhancing and fluorescent tumor were removed and sent for pathologic analysis [Figure 3]. Further molecular characterization demonstrated: Grade 3 Diffuse Astrocytoma; IDH wild-type, MIB index 7%; and MGMT promotor methylation. Postoperatively, no focal neurological deficits were identified. MRI obtained on postoperative day 2 showed resection of the enhancing lesion and non-enhancing residual T2 hyperintense suspected disease at the superior margin [Figure 4].

Figure 2:

Intraoperative view of fluorescent, pathologic tissue visualized through a small corticotomy window. Photo taken at the onset of the resective portion of the surgery, approximately 33 h after administration of 5-aminolevulinic acid. Normal brain parenchyma did not fluoresce and all pathologic specimens that fluoresced were positive for tumor.

Figure 3:

Intraoperative navigation depicting location of biopsy sample and visualized fluorescence under blue-light illumination in the (a) coronal plane, (b) sagittal plane, (c) axial plane, and (d) microscope luminescence control window. The time stamp indicates approximately 32 h after initial administration of 5-aminolevulinic acid. The blue lines in (a), (b), and (c) indicate location of fluorescent biopsy sample depicted in (d).

Figure 4:

Postoperative T1-weighted (a and c) pre-contrast and (b and d) post-contrast magnetic resonance imaging demonstrating complete removal of the contrast-enhancing tumor.

IRB approval was not obtained as this is a case report, negating the requirements for review. The patient’s identity was not disclosed or compromised.

DISCUSSION

The use of 5-ALA FGS as an adjunct for visualization and resection of GBM was approved in June 2017. Since then, there have been multiple articles reporting the efficacy, dosing, and outcomes relative to the volume of tumor resected.[5,8] However, there is limited information regarding the upper temporal limits of sufficient brain tissue fluorescence at the recommended dose of 20 mg/kg.

The rationale for exogenous 5-ALA administration 2–4 h before anesthetic induction is predicated on both the aforementioned dose-response studies and the likelihood that anesthetic administration, patient positioning, setup, craniotomy, and initial macroscopic white-light tumor debulking constitute the initial 3–4 h time period after 5-ALA administration, with the anticipated microscopic blue-light tumor resection occurring in the 4–7 h time frame after dosing.[2,26,27] Expert opinion has further cautioned that if surgery is unexpectedly delayed, one should not cancel surgery strictly on the basis of non-adherence to the classically described fluorescence time window.[28]

ALA is an endogenous metabolite of the mitochondria, which is further metabolized to produce protoporphyrin IX (PpIX). Exogenous/oral 5-ALA is thought to be preferentially metabolized by cells that undergo a high rate of proliferation (i-67, MIB-1 index, and WHO grade).[10,15] The accumulation of the metabolite PpIX allows for intraoperative fluorescence under deep blue light (wavelength filter of 375–440 nm), thereby providing differentiation of high-grade glial tissue from normal parenchyma. The current recommended time to surgery after oral administration of 5-ALA is 2–4 h. Industry-sponsored clinical studies have shown a mean half-life of 0.9 (0.8–1.3) h at the recommended dose, while the maximum concentration of PpIX metabolite was found to occur at a median value of 4 (1.2–7.8) h.[14] Dose-dependent analysis performed by Michael et al. also suggests that increasing doses of 5-ALA are associated with higher rates of gross total resection with lower residual tumor volume when compared to standard dosing in patients with GBM. However, to the best of the authors’ knowledge, there are no studies comparing the fluorescence intensity of brain tissue as a function of time after administration or plasma concentration of 5-ALA.[15,16]

There are many factors that can affect the active metabolic plasma concentration of 5-ALA, including antibiotics and seizure medications such as phenytoin.[6,16] However, our patient did not receive antibiotics before his fever episode instead receiving a standard perioperative first-generation cephalosprin shortly before incision on the day of the surgery. The patient had no remote history of medication use that would affect elimination (including Keppra), nor evidence of hepatorenal dysfunction that would prolong the excretion of 5-ALA. In vitro studies of the WHO Grade 3, human glioma cell lines have shown that IDH1 mutation is associated with a delay in 5-ALA metabolism and consequent fluorescent activity; however, our patient was found to be IDH1 wild-type. [Figure 3] depicts a fluorescent tissue sample at 32 h post 5-ALA dosing, the longest reported example of its kind.

Irrespective of the degree of metabolic clearance, tumor fluorescence with 5-ALA is often heterogeneous.[5] Solid tumor will fluoresce as red, whereas vaguely fluorescent pink tissue beyond the border of MRI T1-Gd enhancement has been described to represent infiltrating tumor both with positive predictive values >92%.[5,7] [Figure 2] depicts tumor fluorescence between 24 and 33 h after initial 5-ALA dose. Factors that may limit visualization of tissue fluorescence include the depth and breadth of the surgical bed and their subsequent impact on the amount of excitatory blue light that can be delivered to the metabolite PpIX-containing tumor tissues. In addition, photobleaching with prolonged illumination can limit visualization of fluorescent tumor.[1,2,9,11] While the ongoing degradation of photoactive PpIX cannot be excluded, the resection of weakly fluorescent and non-fluorescent tissue should still be considered with MRI, intraoperative neuronavigation, and direct visualization of abnormal tissue without damage to eloquent brain tissue.

CONCLUSION

The prospect of working outside the recommended 2–4 h time frame from the administration of 5-ALA to induction of anesthesia allows for greater flexibility in the event of unanticipated scheduling constraints. Our findings also raise the plausibility of whether patients may take 5-ALA the evening before surgery as opposed to 3–5:00 AM the day of surgery. Further evaluation of the temporal characteristics of tissue fluorescence following 5-ALA administration in humans undergoing brain tumor resections would be of value.