Neoadjuvant chemotherapy (NACT) for locally advanced breast cancer (LABC), apart from increasing breast conservation rates, also provides an opportunity to assess tumour response to chemotherapy, with Pathological Complete Response (pCR) described as an independent prognostic factor and a surrogate marker for better outcome and survival. Our primary aim was to identify clinical and pathological factors associated with pCR following NACT in patients with LABC treated at our institution. Our secondary aim was to analyze the impact of pCR and associated factors on disease free survival (DFS) and overall survival (OS). A retrospective analysis of LABC patients treated with NACT between Jun 2011 and Dec 2013. Clinical and histological variables were analyzed for association with pCR (no invasive or in situ carcinoma in breast or axillary lymph nodes). Kaplan-Meier curves and Cox regression model was used for survival analysis. All values were twosided, and statistical significance was defined as p < 0.05. 240 patients were included. The median tumor size was 6 cm, with T4 disease in 49.8 %. 45 % of tumors were of low grade (G1 + G2) and 53.8 % of high grade (G3). Estrogen Receptor (ER) was positive in 70.8 %, progesterone receptor (PR) in 53.3 % and Her2 in 38.8 %. The preferred NACT regimen was sequential anthracycline and taxane and 88.8 % of patients received this regimen. Of 93 potential Her2 Positive patients, only 23 received trastuzumab. Overall 23.2 % patients had pCR. At median follow up of 21 months (range, 3-42), 16.3 % of patients had recurrent disease, and 6.7 % had died. High tumor grade (p = 0.04), PR negative status (p < 0.01) and trastuzumab treatment (p = 0.01) were significant predictors of pCR in univariate analysis. On multivariate analysis PR negativity (OR 3.2, 95 % CI = 1.6 to 6.04, p = 0.001) and Trastuzumab use (OR 0.24, 95 % CI = 0.1 to 0.6, p = 0.004) were significant. Patients with pCR had positive associations with survival (p < .02,OS& .02,DFS) and interestingly PR positivity had positive association with DFS (p = 0.02) in Kaplan-Meier curves. On Cox regression, PR positivity (HR = 0.3, p < 0.01) and pCR (HR = 0.2, p < 0.01) correlated with DFS, though not with early OS. for the PR positive patients were paradoxical. Though less likely to have pCR (15 %, vs 32 % if PR negative), they had better DFS (p = 0.02), and achieving pCR had no survival benefit in this group. In contrast, PR negative patients, irrespective of ER status, had a high pCR rate, and achieving pCR had survival advantage (p < 0.05,DFS& p < 0.02,OS). PR negative patients without pCR had the worst DFS (p < 0.01) among all. High grade and Trastuzumab treatment as predictors of pCR, and pCR as a surrogate marker for survival are well recognized, and are supported by our findings. In present cohort, PR negativity showed prognostic importance independent of ER status. However these results were derived from sub-group, post-hoc analysis of data from a pre-existing cohort, without 'a-priori' hypothesis for survival analysis in relation to PR. These "hypothesis generating" results need confirmation by a well-designed prospective cohort or a randomized trial.
Keywords: Breast cancer; Impact on survival; Neoadjuvant chemotherapy; Pathological complete response; Predictors; Progesterone receptor.