Long-term outcomes for neoadjuvant versus adjuvant chemotherapy in operable breast cancer patients with hormone receptor-positive, HER2-negative

Objective To compare the long-term survival outcomes of patients with operable hormone receptor-positive, human epidermal growth factor receptor 2-negative (HR+/HER2-) breast cancer at stage II and T3N1M0 receiving neoadjuvant chemotherapy (NACT) versus adjuvant chemotherapy (ACT) using data extracted from the Surveillance, Epidemiology, and End Results (SEER) database. Methods Data on 33,552 patients were extracted from the SEER database between 2010 and 2020. Patients were categorized into the NACT group and the ACT group. The primary endpoints were overall survival (OS) and breast cancer-specific survival (BCSS). After propensity score matching (PSM), Kaplan-Meier survival analysis and Cox proportional hazards regression models were used to assess the effects of NACT versus ACT on survival outcomes. Subgroup analysis was performed to explore the impact of various clinical and pathological factors on survival outcomes. Results After PSM, the NACT group showed significantly inferior 5-year OS (87.4% vs 91.8%, P0.0001) and BCSS (89.3% vs 93.7%, P0.0001) compared to the ACT group. Even among patients achieving objective response to NACT, multivariate Cox regression demonstrated significantly higher risks of breast cancer-specific death (HR = 1.42, 95%CI: 1.17-1.73, P0.001) and all-cause death (HR = 1.31, 95%CI: 1.10-1.57, P = 0.002) versus the ACT group. Conclusion In patients with operable HR+/HER2- breast cancer at stage II and T3N1M0, NACT was associated with inferior OS and BCSS compared to ACT. These findings suggest caution when selecting NACT for this patient subset.