Pathological responses and long-term outcome analysis after neoadjuvant chemotheraphy in breast cancer patients from Kuwait over a period of 15 years.

BACKGROUND AND OBJECTIVES: The attainment of pathological complete response (pCR) after neoadjuvant chemotherapy has been taken as a surrogate marker for disease-free survival and overall survival. This is however dependent on various other parameters such as stage, grade, and biologic markers. DESIGN AND SETTINGS: This is a retrospective study of 365 patients with histologically confirmed non-met.astatic breast cancer patients treated with neoadjuvant chemotherapy at the Kuwait Cancer Control Centre between 1998 and 2009. PATIENTS AND METHODS: A total of 365 breast cancer patients who had received neoadjuvant chemotherapy from 1998-2009 were analyzed for the relationship of pCR with hormone status, Her2 status, histopathological subtype. Survival analysis was also conducted.
RESULTS: Hormone receptor (HR) negative tumors had a higher pCR as against HR positive tumors, and the highest pCR in our analysis of pathological subtypes were seen in the HR+, Her2neu + and HR-, Her2neu + group. In our study, we could make out the paradoxes that well differentiated, and HR positive tumors had a better survival in spite of having lower pCR. The luminal A subtype also had a better overall survival than the triple negative subtype in spite of having lower pCR with neoadjuvant chemotherapy.
CONCLUSION: Though the achievement of pCR retains its significance, it is more prognostic in HR negative tumors. The importance of HR receptor status, grade, and histopathological subtype in the long-term survival has been emphasized.

Neoadjuvant chemotherapy is the standard of care for locally advanced carcinoma breast and has been increasingly used in resectable breast cancer.1 Responses after neoadjuvant chemotherapy has been taken as a surrogate marker for disease-free survival (DFS) and overall survival (OS). With a better understanding of chemotherapeutic regimens and integration of targeted therapies into neoadjuvant regimens, there have been better responses in the recent years. The responses to chemotherapy are, however, dependent on various other parameters such as stage, grade, and biologic markers. The effectiveness of the achievement of pathological complete response (pCR) in various breast cancer subtypes with respect to survival has not been consistent in most studies.2

We did a retrospective analysis of patients with non-metastatic breast cancer who were treated in Kuwait with neoadjuvant chemotherapy. The complete pathological responses with respect to various parameters were studied. The 10-year-survival analysis was also conducted with respect to complete pathological responses and with respect to other biologic factors and pathological subtypes. The prognostic value of pCR was also studied in various clinical pathological subgroups.

PATIENTS AND METHODS

This is a retrospective study of 365 patients with histologically confirmed non-metastatic breast cancer who weretreated with neoadjuvant chemotherapy at the Kuwait Cancer Control Centre between 1998 and 2009. The patients had all undergone core biopsy for diagnosis along with ER, PR, and Her2 testing. They were staged according to American Joint Committee on Cancer Guidelines (AJCC), and the medical records were reviewed for clinical parameters and survival assessment.

Histopathological examination

All the tumors were classified into different subtypes by the WHO classification. The histopathological records were reviewed for ER, PR, and Her2neu results. ER and PR statuses were assessed by immunohistochemistry (IHC) studies with a threshold of 10% or more to be classified as positive (which was the standard during the period of our study). Tumors with either ER or PR positivity were taken as hormone receptor (HR) positive. Her2 was assessed by IHC according to the Herceptin scoring system and a score 3+ was taken as positive. Patients with an equivocal IHC score of 2+ had fluorescence in situ hybridization (FISH) amplification done with a threshold Her2neu/CEP17 ratio ≥2 taken as positive or amplified. As a protocol all histopathologcal and IHC slides were independently reviewed by 2 pathologists.

Treatment

Anthracycline- and taxane-containing combinations were employed in the neoadjuvant schedules. Most patients received either anthracycline-containing (42/365-11.5%) or anthracycline- and taxane-containing regimens (302/365-82.7%) with a few patients receiving taxane only (16/365-4.3%) or nonanthracycline non-taxane regimens (5/365-1.3%). The chemotherapeutic regimens used were either FEC (fluorouracil 500 mg/m2 IV, epirubicin 100 mg/m2 IV, and cyclophosphamide 500 mg/m2 IV on day 1, every 3 weeks), AC (doxorubicin 60 mg/m2 IV and cyclophosphamide 600 mg/m2 IV on day 1, every 3 weeks), TE(docetaxol 75 mg/m2 with epirubicin 75 mg/m2 every 3 weeks), FEC-D (4 cycles of FEC followed by 4 cycles of docetaxol 80–100 mg/m2 day 1, every 3 weeks), AC-T (4 cycles of AC followed by weekly taxol 80 mg/m2 for 12 weeks or 175 mg/m2 every 3 weeks), or TE (docetaxol 75 mg/m2 with epirubicin 75 mg/m2 every 3 weeks) for 6 to 8 cycles. Among the total 103 patients with Her2 positive disease, maintenance trastuzumab was given to 72 patients but only 44 among them received neoadjuvant trastuzumab. Trastuzumab was either given as 4 mg/kg initial loading dose followed by 2 mg/kg maintenance weekly or 8 mg/kg loading dose followed by 6 mg/kg maintenance 3 weekly for a total period of 1 year. All patients underwent surgery either at the end of neoadjuvant chemotherapy (203/365-55.6%) or as an interval procedure (162/365-44.4%). The surgery done was mastectomy or breast-conserving surgery, and the axilla was treated by either axillary dissection or sentinel lymph node dissection. Radiotherapy was administered after the completion of chemotherapy and surgery. Adjuvant hormonal therapy was either with tamoxifen or with aromatase inhibitors (letrozole or anastrozole).

Assessment of response

The absence of invasive carcinoma in both breast and axillary lymph nodes in the post-surgery specimen was taken as pCR. Residual ductal carcinoma-in-situ was included in the pCR category. The post-neoadjuvant chemotherapy pathological stage, Tumor (T) and Nodal (N) statuses according to AJCC were among the factors that were studied in relation to DFS and OS.3

Statistical analysis

A comparison between various parameters and pCR was done using chi-square test and Fisher exact statistical tests, whereas Kaplan–Meier method was used to perform the analysis of survival in various subgroups. The log-rank or Breslow statistic was used for the univariate comparisons of median survival and the rate at specific time endpoints (with a 95% CI). Hazard ratio for survival with respect to various parameters was done by Cox regression analysis. A P value of <.05 was taken as significant. All analyses were carried out using the IBM-SPSS statistical software (version 20, International Business machines Corporation, USA). The median time period of follow-up was 49 months (7–163 months). DFS was measured from the date of first diagnosis to the date of first local or distant metastasis or last follow-up. OS was defined as the date of first diagnosis to death from any cause. Surviving patients without recurrence were censored at the date of last follow-up.

RESULTS

Patient characteristics

A total of 365 patients were analyzed retrospectively. The median age of our cohort was 50 years. There were a larger number of premenopausal patients (64.9%) and majority (83.5%) were stage III. HR positivity was seen in 58.6%, and 40.8% had a high-grade tumor. Our population had a higher number of triple negative tumors (21.3%) than most other series. The details of various characteristics and pCR rates in each subgroup are shown in Table 1.

Table 1

Patient characteristics and pCR.

	Total No (%)	pCR	pCR (%)	P value
Overall	365	50	13.7
Age of patient
<50 years	183 (50.2%)	24	13.1%	.745
>50 years	182 (49.8%)	26	14.2%
Menstrual status
Premenopausal	237 (64.9%)	36	15.1%	.26
Postmenopausal	128 (35.1%)	14	10.9%
Clinical stage of disease
IIA/IIB	41 (11.2%)	6	14.6%	.90
IIIA/IIIB/IIIC	305 (83.5%)	40	13.1%
Inflammatory	19 (5.3%)	4	21%
Clinical lymph node
Present	324 (88.7%)	45	13.8%	.766
Not present	41 (11.3%)	5	12.1%
Histopathological type
IDC	338 (92.6%)	48	14.2%	0.542
ILC	19 (5.2%)	1	5.2%
Others	8 (2.2%)	1	12.5%
Grade of tumor
Grade I	29 (7.9%)	0	0%	.009
Grade II	141 (38.6%)	13	9.2%
Grade III	149 (40.8%)	28	18.7%
Unknown	46 (12.7%)	9	19.5%
Hormone receptor (HR) status
HR+	214 (58.6%)	22	10.2%	.024
HR−	151 (41.4%)	28	18.5%
Her 2 status
Her2+	103 (28.2%)	22	21.3%	.027
With trastuzumab	44	15	34%
Without trastuzumab	59	7	11.8%
Her2−	239 (65.5%)	26	10.8%
Her2 unknown	23 (6.3%)	2	8.6%
Pathological Subtype
HR+ Her2−	162 (44.4%)	13	8%	.022
HR+ Her2+	47 (12.9%)	9	19.1%
HR− Her2+	55 (15%)	13	23.6%
HR− Her2−	78 (21.3%)	13	16.6%
HR+ Her2 unknown	13 (3.6%)	0	0%
HR− Her2 unknown	10 (2.8%)	2	20%
Surgical type
Mastectomy	296 (81%)	40	13.5%	.831
Wide excision	69 (19%)	10	14.4%

Pathological complete response rates

The overall pCR was 13.7%. The achievement of pCR was not significant with respect to the age, menstrual status, and initial clinical stage of diagnosis or clinical presence of lymph nodes. Higher pCRs were however seen in inflammatory breast cancer. The most important factors associated with pCR were the biological factors. HR negative tumors had a consistently higher pCR (18.5%) as against HR positive tumors. Similarly Her2 positive tumors had a significantly higher pCR (21.3%) as against Her2 negative tumors. A total of 42.7% patients in the Her2 positive category received trastuzumab accounting for the high pCR rates. The highest pCR in our analysis of pathological subtypes was seen in the HR+, Her2neu+ and HR−, Her2neu+ groups at 19.1% and 23.6%, respectively. The triple negative subtype had a pCR of 16.6%, and the lowest rates were seen in the HR+, Her2neu− group. A total of 18.7% of grade III tumors had pCR as against 0% in grade 1 tumors.

Survival analysis

The median DFS in our population was 103.7 months. The 5-year DFS and OS were 58.9% and 66.5%, respectively.

The DFS and OS of patients achieving pCR were significantly higher than those of patients with no pCR, and the advantage was continuing after more than 10 years of follow-up. Tumor stage, nodal stage, and pathological stage after neoadjuvant chemotherapy was significantly associated with prognosis (P<.001) with worst outcomes for yp T3 T4, yp N2, N3, and yp stage III. The Kaplan–Meier estimates for DFS and OS at 5 years and 10 years are shown in Table 2 and Figure 1, respectively. Table 3 shows hazard ratio for DFS and OS in various categories by Cox regression analysis. Hazard ratio for DFS and OS were higher in grade 3 tumors as against grade 1 and 2 tumors. The most important pathological factor was hormone positivity, with hormone positive tumors showing higher DFS and OS as against negative tumors.

Table 2

Kaplan Meier Estimates of various parameters with respect to 5 year and 10 year DFS.

Parameter	No. of patients	No. of events	Median Survival (months)	5 year DFS		10 year DFS		P value
				%	95%CI	%	95%CI
pCR
Yes	50	11	NR	79.9	68.5–91.3	72	53.8–90.2	.019
No	315	134	86	55.7	49.5–61.9	44.3	34.5–54.1
ypT status
T0	71	18	NR	74	62.8–85.2	69.4	55.6–83.2	.003
T1	133	50	146	61	51.8–70.2	54.8	43.4–66.2
T2	119	55	62	51.8	41.4–62.2	42.8	30–55.6
T3/T4	42	22	59	42.8	22–63.6	0%
ypN status
N0	131	27	NR	80.5%	73.1–87.9	66.3	50.9–81.7	<.001
N1	107	38	126.2	66.5	56.5–76.5	52	35–69
N2	127	80	38.7	32.2	22.8–41.6	25.7	13.5–37.8
yp stage
Stage 0	50	11	NR	79.9	68.5–91.3	72	53.8–90.1	<.001
Stage I	55	10	NR	79.5	67.1–92.3	66.2	39.8–92.6
Stage IIA	74	22	NR	68.3	55.9–80.7	59.9	43.9–75.9
Stage IIB	45	18	124	62.2	46.2–78.2	54.9	37.9–71.9
Stage III	141	84	41	36.3	26.9–45.7	25.5	12.1–38.9
Hormone receptor status
HR positive	214	78	114.1	63.8	56.4–71.2	47.7	34.7–60	.014
HR negative	151	67	84.7	51.9	42.7–61.1	46.7	35.5–57.9
Histopathologic type
HR+Her2−	162	52	NR	68.4	60.4–76.4	52	35–69	.016
HR+Her2+	47	21	103.76	54.9	37.9–71.9	33.5	3.7–63.3
HR−Her2+	55	23	84.7	52.9	36.3–69.3
TN	78	37	51.8	47.7	34.9–60.5	44.5	31.1–57.9	NR
NR-not reached, TN-Triple Negative

Figure 1

A) Kaplan Meier curves showing OS with respect to pCR, B) yp stage and C) hormone receptor status.

Table 3

Cox’s Regression analysis showing Hazard ratio (HR) for various parameters with respect to DFS and OS.

Parameter	DFS		OS
	HR (95%CI)	P value	HR (95%CI)	P value
Complete pathological response
No pCR	2.043 [1.10–3.77]	.023	1.884 [1.05–3.12]	.05
yp T Status
T0/Tis	Reference		Reference
T1/Tmic	1.472 [0.85–2.52]	.161	1.085 [0.62–1.89]	.774
T2	2.001 [1.175–3.40]	.011	1.696 [0.99–2.89]	.053
T3/T4	2.824 [1.512–5.27]	.001	2.852 [1.55–5.233]	.001
yp N status
N0	Reference		Reference
N1	1.727 [1.05–2.82]	.030	1.570 [0.93–2.62]	.085
N2/3	4.041[2.69–6.28]	.000	3.391 [2.16–5.32]	.000
yp Stage
Stage 0	Reference		Reference
Stage I	0.763 [0.32–1.79]	.536	0.575 [0.23–1.43]	.234
Stage IIA	1.293 [0.62–2.66]	.487	1.148 [0.55–2.38]	.712
Stage IIB	1.690 [0.79–3.57]	.171	1.333 [0.61–2.87]	.462
Stage III	3.399 [1.81–6.37]	.000	2.614 [1.39–4.90]	.003
Grade III vs. I/II	1.346 [0.952–1.904]	.093	1.573 [1.101–2.247]	.013
HR positivity	0.675 [1.069–2.056]	.018	0.575 [0.412–0.0804]	.001
Her2 positivity	1.221 [0.850–1.754]	.281	0.492 [0.583–1.295]	.492
Pathology type
HR+Her2−	Reference	.023	Reference
HR+Her2+	1.496 [0.9–2.486]	.120	1 [0.553–1.807]	.10
HR−Her 2+	1.675 [1.024–2.74]	.040	1.357 [0.8–2.30]	.257
Triple Neg.	2.014 [1.32–3.075]	.001	2.265 [1.496–3.43]	.000

Prognostic significance of pathological subtype and their relation to pCR

The 5 year DFS and OS was 68.4% and 73.7% in the HR+Her2−, 54.9% and 74.8% for HR+Her2+, 52.9% and 64.6% For HR−Her2+ and 47.7% and 52.7% for triple negative (Figure 2). Cox regression analysis was done to know how the achievement of pCR affected the DFS and OS in various pathological parameters (Table 4). HR negative tumors who had achieved pCR had a better DFS as against those who had not which was not seen for the HR positive cohorts. Kaplan–Meier curves for the same are shown in Figure 3. Similarly there was a trend towards better DFS in HR−, Her2 positive patients who achieved pCR which was not seen in the other pathological subtypes. Kaplan–Meier survival curves for DFS and OS according to pCR rates for each pathological subtype are shown in Figure 4.

Figure 2

DFS and OS for pathological subtypes.

Table 4

Coxs Regression analysis showing DFS and OS with respect to Complete Pathological response for various biological parameters.

Parameter	DFS		OS
	HR (95%CI)	P value	HR	P value
HR+	0.463 [0.169–1.267]	.134	0.658 [0.239–1.811]	.417
HR−	0.468 [0.214–1.026]	.05	0.486 [0.222–1.062]	.071
Her2+	0.266 [0.082–0.862]	.027	0.470 [0.142–1.557]	.217
Her2−	0.635 [0.293–1.375]	.250	0.690 [0.319–1.494]	.347
Pathological subtypes
HR+Her2−	0.620 [0.193–1.988]	.421	0.728 [0.228–2.34]	.594
HR+Her2+	0.237 [0.031–1.786]	.162	0.475 [0.06–3.757]	.481
HR−Her2+	0.278 [0.065–1.191]	.085	0.42 [0.96–1.829]	.248
Triple negative	0.531 [0.188–1.501]	.232	0.511 [0.182–1.437]	.203

Note: All values are for patients who have achieved pCR to those who have not.

Figure 3

A) DFS according to pCR in hormone receptor positive and B) hormone receptor negative tumors.

Figure 4

DFS for each pathological subtype with respect to pCR.

In the subgroup analysis of patients who had achieved pCR, triple negative patients did much worse than all other subgroups (Table 5).

Table 5

Kaplan Meier estimates for DFS and OS at 4 years in patients who have achieved pCR (N=48).

	Patients (N)	Events DFS	DFS		Events OS	OS
			%	95% CI		%	95% CI
Histological subtype
HR+Her2−	13	3	84.6	64.6–100	3	83.3	62.2–100
HR+Her2+	9	1	88.9	67.9–100	1	85.7	59.3–100
HR−Her2+	13	2	84.6	64.6–100	2	84.6	64.6–100
Triple Neg	13	4	69.2	43.6–94.8	4	67.3	39.7–94.9

DISCUSSION

Neoadjuvant chemotherapy results in equivalent efficacy and increased breast conservation as compared to standard adjuvant therapy.1 Use of primary systemic treatment allows for an in vivo assessment of chemotherapy sensitivity, based on the endpoint of pCR.4,5

Our retrospective analysis was aimed at determining the pCR rates and their significance in a Middle Eastern population. Our cohort consisted of more triple negative patients and younger premenopausal patients as compared to other studies.6

Molecular subtypes of human breast cancer were first described by Perou et al in 2000.7 In clinical practice, IHC is used to approximate biological subtypes as follows: HR+Her2−, HR+Her2+, HR−Her2+ and Triple negative [HR−Her2−].8

pCR has been shown to improve long-term survival and has been accepted as a surrogate endpoint.9 In our population, the overall pCR rates were 13.7%. This is lower than those reported from the western population in spite of having higher percentage of triple negative patients.10 Patients who achieved pCR in our study had a better 10 year DFS and OS.

In addition to pCR, HR status and histopathological subtype, the pathological stage after neoadjuvant chemotherapy also affected the DFS and OS, which is similar to previously reported.11 Post neoadjuvant T and N status also maintained their prognostic significance. In our analysis, HR positivity has more significance irrespective of Her2 status. HR+Her2+/− patients had better survival than both HR−Her2+ and triple negative patients. Hazard ratios for HR+Her2− and HR+Her2+ patients were equal for OS. Darb Esfahani et al has previously reported a 3-year survival of 90% for HR+ tumors irrespective of Her2 status as against 33% in HR−Her2+ and 65% in Triple negative tumors.12

In our study, we could make out the paradoxes that well differentiated and HR positive tumors had a better long-term survival in-spite of having lower pCR. Luminal A subtype also had a better OS than triple negative subtype in spite of having lower pCR with neoadjuvant chemotherapy. These findings have been previously reported from various other studies13–15 von Michkwitz et al has reported that subgroups considered to have slowly proliferating tumors, pCR is not associated with prognosis, whereas in subgroups with highly proliferating tumors, pCR can discriminate between patients with good and poor prognosis accurately. The prognostic impact of pCR is highest in Her2-positive (non-luminal) and TN tumors, where patients achieving pCR show a prognosis comparable to that of patients with luminal A tumors.2

Thus pCR is a strong prognostic factor in patients with HR negative tumors. In our analysis, HR negative patients achieving pCR had a statistically significant better DFS (P=.05). When DFS was analyzed according to pCR for biological subtypes, only the HR−Her2+ subtype was nearing significance. Patients with hormone positive subtypes should thus not be included in clinical trials where pCR is the endpoint. 16

Our analysis has significant drawbacks in spite of being the largest from the Middle East. It is a retrospective study done over a prolonged period of time. During this period significant change in the treatment of breast cancer has occurred including the approval of trastuzumab in the neoadjuvant setting. Also certain subsets of patients had very small numbers, making comparisons difficult.

In conclusion, this analysis of 365 women treated in Kuwait, confirms the prognostic value of pCR. HR status, tumor grade, and histopathological subtype are more important in determining a long-term survival. pCR as an endpoint for survival is thus more important in HR negative tumors.