The role of radiation therapy in the multidisciplinary management of male breast cancer: A systematic review and meta-analysis on behalf of the Clinical Oncology Breast Cancer Group (COBCG).

Male breast cancer (MaBC) is an uncommon disease. It is generally assimilated to post-menopausal female breast cancer and treated accordingly. However, the real impact of radiation therapy, after both mastectomy and breast conservation, has yet to be established. We performed a systematic review and meta-analysis to assess the clinical impact of radiation therapy in MBC patients to support the clinical decision-making process and to inform future research. We performed a systematic search of 'male', 'breast', 'cancer', 'radiotherapy' and corresponding synonyms on PubMed/MEDLINE and EMBASE databases. We included interventional studies reporting on radiation therapy effect on overall survival (OS) in MBC patients. Reviews, editorials, letters to the editor, conference abstracts and case reports, and studies with less than 20 MaBC patients or without data on OS were excluded. We extracted relevant characteristics and outcomes for each study, including the hazard ratio (HR) for OS, after adjustment for potential confounders. We calculated an overall adjusted hazard ratio (aHR) for OS for patients receiving radiation therapy compared to those who did not. A random effect model was used. The search strategy yielded 10,260 articles. After removal of duplicates (n = 8254), 2006 articles remained and underwent abstract screening. A total of 168 manuscripts was selected for full text screening. After full text screening, 22 articles were included in the qualitative systematic review. Among them, 14 were included in the quantitative synthesis, reporting on 80.219 MaBC patients. A statistically significant reduction in the risk of death was observed for patients receiving radiation therapy, with a pooled aHR = 0.73 (95 %CI: 0.66-0.81) for OS. Significant heterogeneity among reported aHR estimates was seen (I2=77 %). A significant clinical benefit on OS has been observed when including radiation therapy in the therapeutic algorithm of patients with MaBC. These findings, which are based on retrospective studies and tumour registry reports, deserve further investigation to identify MaBC patient subgroups who most benefit from radiation therapy.