Post Mastectomy Radiation Therapy Impact on Clinical Outcomes of Male Breast Cancer: A Meta-Analysis of Comparative Studies

Abstract

Male breast cancer accounts for less than 1 percent of all cancer diagnoses in men. Because it is rare, it does not lend itself to large, randomized trials. In general, the approach to the treatment of early, non-metastatic male breast cancer has largely been extrapolated from female breast cancer trials though it is deemed to be a different disease. Data on early-stage post mastectomy radiation therapy (PMRT) is limited, and its benefits remain unclear. We conducted this meta-analysis to determine the impact of PMRT on recurrence patterns and survival outcomes using the available male breast cancer data. A review of the medical literature was conducted using online databases. Inclusion criteria consisted of English language, diagnosis of invasive non-metastatic male breast cancer (MBC), comparative studies of PMRT versus none, and studies that reported the incidence of local and distant recurrences as well as survival data in the compared arms. A meta-analysis using the Mantel-Haenszel method for calculating the weighted pooled relative risk (RR) under the fixed effects model was conducted. Subsequently, the heterogeneity statistic was incorporated to calculate the summary RR under the random effects model. Ten retrospective comparative studies with 3912 patients were included and analyzed. Eight studies reported survival data. Six and three studies reported local and distant recurrence incidence, respectively. PMRT did not have an impact on overall survival or distant recurrences. However, PMRT significantly lowered the RR of locoregional recurrences (RR = 0.53, 95% CI 0.31-0.92). In addition, when survival was analyzed by TNM stage and N status, PMRT was found to have a significant reduction in RR of death in stage III (RR = 0.85, 95% CI 0.75-0.97), N1 (RR = 0.77, 95% CI 0.61-0.98), and N2 (RR = 0.61, 95% CI 0.49-0.78) disease. This is the first meta-analysis to show that PMRT is associated with a lower relative risk of death in stage III MBC as well as N1 and N2 disease. It also demonstrates a significant reduction in RR of locoregional recurrences. In the absence of randomized clinical trials, it represents the most compelling data supporting the use of PMRT in this MBC patient population using MBC data.