Real-world evidence of survival outcomes in breast cancer subtypes after neoadjuvant chemotherapy in a Brazilian reference center.

Abstract

Background: Neoadjuvant chemotherapy (NAC), traditionally used for locally advanced disease, is now applied for operable disease, particularly to treat aggressive breast cancer (BC). This study aimed to characterize the pathological complete response (pCR) and its relationship with overall survival (OS) and disease-free survival (DFS) among BC patients receiving NAC in a Brazilian public reference center, as well as the association between pCR and BC subtypes.

Methods: A retrospective cohort study used a comprehensive BC database from a Brazilian women's health reference center, including patients diagnosed between 2011 and 2020 who underwent NAC. We collected demographic, cancer-specific, and treatment-related data, analyzing OS and DFS based on pCR status using the semiparametric Kaplan-Meier method, with the date of BC diagnosis as the starting point.

Results: The study included 1,601 patients, with an average age of 49 years and a majority presenting stage IIIa disease (35%). Most had invasive nonspecial type (NST) BC (94%), and a significant portion (86.7%) exhibited a Ki-67 index <14. The overall pCR rate was 22.7%, with higher frequencies observed in the triple negative and luminal B subtypes. Patients who achieved pCR had significantly higher survival rates (89% alive vs. 61%, P<0.001) and better DFS (90% vs. 66%, P<0.001), except in the luminal A subtype, where pCR did not correlate with improved OS or DFS.

Conclusions: These updated real-world data (RWD) from BC patients who underwent NAC in Brazil revealed a pCR rate of 22.7% in all cancer subtypes and stages. pCR was not associated with better outcomes in patients with luminal A, contrasting with other subtypes.