The role of adjuvant chemotherapy in stage I-III male breast cancer: a SEER-based analysis.

Background And Aims: Male breast cancer is an uncommon disease. The benefit of adjuvant chemotherapy in the treatment of male breast cancer patients has not been determined. The aim of this study was to explore the value of adjuvant chemotherapy in men with stage I-III breast cancer, and we hypothesized that some male patients may safely skip adjuvant chemotherapy.

Methods: Male breast cancer patients between 2010 and 2015 from the Surveillance Epidemiology and End Results database were included. Univariate and multivariate Cox analyses were used to analyse the factors associated with survival. The propensity score matching method was adopted to balance baseline characteristics. Kaplan-Meier curves were used to evaluate the impacts of adjuvant chemotherapy on survival. The primary endpoint was survival.

Results: We enrolled 514 patients for this study, including 257 patients treated with chemotherapy and 257 patients without. There was a significant difference in overall survival (OS) but not in breast cancer-specific survival (BCSS) between the two groups ( < 0.001 for OS and  = 0.128 for BCSS, respectively). Compared with the non-chemotherapy group, the chemotherapy group had a higher 4-year OS rate (97.5% 95.2%,  < 0.001), while 4-year BCSS was similar (98% 98.8%,  = 0.128). The chemotherapy group had longer OS than the non-chemotherapy group among HR+, HER2-, tumour size >2 cm, lymph node-positive male breast cancer patients ( < 0.05). Regardless of tumour size, there were no differences in OS or BCSS between the chemotherapy and non-chemotherapy cohorts for lymph node-negative patients (OS:  > 0.05, BCSS:  > 0.05). Adjuvant chemotherapy showed no significant effects on both OS and BCSS in patients with stage I (OS:  = 0.100, BCSS:  = 0.858) and stage IIA breast cancer (OS:  > 0.05, BCSS:  > 0.05).

Conclusion: For stage I and stage IIA patients, adjuvant chemotherapy could not improve OS and BCSS. Therefore, adjuvant chemotherapy might be skipped for stage I and stage IIA male breast cancer patients.