Survival benefit of adjuvant chemotherapy in elderly patients with stage I triple-negative breast cancer: a cohort study based on the SEER database.

Background: This study analyzed the trend and prognostic role of postoperative adjuvant chemotherapy (POCT) in patients with stage I triple-negative breast cancer (TNBC) aged more than 65 years. In addition, the relationship between POCT and survival rate was also determined. Methods: The Surveillance, Epidemiology, and End Results (SEER) database was collected to determine 3,307 TNBC elderly women aged ≥65 years between 2010 and 2016, and they were divided into POCT and non-POCT groups. Propensity score matching (PSM) method was used to offset the differences in baseline characteristics between the groups. Kaplan-Meier plots were tested to contrast overall survival (OS) and breast cancer-specific survival (BCSS) between the two groups. The Cox proportional hazard model was constructed to assess the prognostic factors affecting OS and BCSS. Results: Younger age, higher histological grade, married, postoperative radiotherapy, lumpectomy, larger tumor, and closer year of diagnosis were related to an enhanced likelihood of adjuvant chemotherapy. After PSM, POCT was related to increased 5-year OS [hazard ratio (HR): 0.571, 95% confidence interval (CI): 0.432-0.753, respectively], without significant difference in BCSS improvement. Exploratory subgroup analysis demonstrated that POCT contributed to OS improvement in both IA and IB patients, but did not improve BCSS in IA and IB patients. Conclusions: In elderly patients ≥65 years, POCT improved 5-year OS in stage I TNBC patients, while further exploration with larger prospective trials are needed.