Real-world data on pathological complete response and outcomes in hormone-receptor–positive breast cancer: An Indian experience.

e13045 Background: The data on the pathological complete response (pCR) after neoadjuvant chemotherapy (NACT) for hormone receptor-positive breast cancer (BC) in the real world are limited from Indian subcontinent. This study aimed to identify various clinicopathological features associated with achieving pCR and its impact on invasive disease-free survival (iDFS) and overall survival (OS). Methods: We retrospectively analyzed data from hormone receptor-positive breast cancer patients treated between 2013 and 2023 at All India Institute of Medical Sciences (AIIMS), New Delhi, the largest tertiary care facility in India. The primary objective was to assess pCR rates and their correlation with iDFS and OS. pCR was assessed using the miller-payne grading system where grade 5 signifies complete response. The NACT (sequential anthracycline followed by taxane and/or targeted therapy), adjuvant regimes, and ovarian function suppression were given as per institution protocol. Results: A total of 2245 patients were screened, and 1051 (46.81%) patients were eligible for neoadjuvant therapy. The median age of our cohort was 48 years (22-84 years). Of these, 410 patients (39%) were HR+/Her2- and 641 patients (60.98%) were HR+/Her2+. A total of 52.5% of patients were premenopausal. The clinical stage (AJCC 7th edition) was: stage II in 43%, stage III in 51%, and stage IV (oligometastatic BC) in 4% of cases. Breast conservation surgery was performed in 25.3% of the patients. The rate of pCR was 32.85% in the entire patient cohort whereas it was 12.5% in the HR+/Her2- subgroup and 45.5% in the HR+/Her2+ subgroup. In multivariate analysis revealed that nodal positivity (OR: 0.44, p = 0.03) and HR+/Her2+ status (OR: 4.09, p = 0.004) were independently associated with pCR. The median duration of follow-up was 4.1 years. The 5-year iDFS was 76.6% and OS was 90.1%. pCR did not correlate with iDFS and OS in both HR+/Her2- subgroup (p = 0.96, HR 0.98; 95% CI-0.52-1.85) and the HR+/Her2+subgroup (p = 0.81, HR 0.92; 95% CI-0.48-1.75). Conclusions: This is the largest real-world Indian study evaluating the impact of pCR on outcomes in hormone-positive BC. Our study did not establish a significant association between pCR and survival even in the HER2-positive subgroup. This study hypothesized that pCR can serve as a reliable marker for escalating treatment by incorporating CDK 4/6 inhibitors in the adjuvant or neoadjuvant setting irrespective of Her2 neu status.