Clinicopathological Features and Survival Outcomes of Metaplastic Breast Carcinoma - An Observational Multi-Centric Study.

Purpose: To describe the clinicopathological features, and subtypes of metaplastic breast cancer (MpBC) in Pakistan and further to understand its response to treatment, including region-specific survival outcomes. Patients and Methods: This retrospective cohort study was conducted at two private tertiary care hospitals in Karachi, Pakistan. Our selection criteria included a total of 215 patients who were diagnosed with MpBC at an age older than 18 years from 1994 to 2021. Data regarding clinicopathological features, staging, receptor status, treatment modalities, recurrence, and survival was obtained. Death was scored as an event, and patients who were alive were censored at the time of the last follow-up. Results: The incidence of MpBC at our study centers is 3.21%. The median age of diagnosis was 50 years (range 22 to 80 years) and most patients presented at Stages II (45.1%) and III (44.2%). Among patients who received neoadjuvant chemotherapy, 31.7% achieved complete pathological response. The 3-year survival of those who received neoadjuvant chemotherapy was 96%. During our study, 19.1% of patients died and the median survival duration was 9 years 7 months 9 days. Survival of patients was significantly lower in patients who had metastasis (p-value = 0.042) and those who had tumor recurrence (p-value = 0.001). Conclusion: Metaplastic breast cancer is an extremely rare variant of breast cancer with features that exist as a spectrum. Our study demonstrated considerable success with the use of neoadjuvant chemotherapy. The pathological complete response achieved in our study is one of the highest ever reported. Our success, though limited, warrants further research in the use of neoadjuvant chemotherapy in MpBC.