Post‐mastectomy Radiotherapy for pT3N0 Breast Cancers: A Retrospective,Multi‐Institution Review

The role of post‐mastectomy radiotherapy for pT3N0 breast cancers remains undefined. The purpose of this study was to report institutional outcomes for women with pT3N0 breast cancers treated with and without post‐mastectomy radiotherapy. We collected data from two large tumor registries on pT3N0 breast cancers diagnosed between 1985 and 2014. Kaplan–Meier estimates were used to analyze freedom from local‐regional recurrence (FFLR), relapse free survival, and overall survival. This analysis identified 93 women with pT3N0 breast cancers. Of these, 53 received post‐mastectomy radiotherapy and 40 did not. Median follow‐up was 6.2 years and 5.3 years in the non‐post‐mastectomy radiotherapy and post‐mastectomy radiotherapy cohorts, respectively. Women not undergoing post‐mastectomy radiotherapy were more likely to be diagnosed in the 1980s and 1990s and were less likely to receive systemic therapies than women receiving post‐mastectomy radiotherapy (p < 0.05). There was a trend toward increased FFLR in the women receiving post‐mastectomy radiotherapy (p = 0.15). FFLR in the post‐mastectomy radiotherapy cohort was 98% at both 5 and 10 years. For women not receiving post‐mastectomy radiotherapy, FFLR was 88% at both 5 and 10 years. Women not receiving post‐mastectomy radiotherapy in our study had an isolated local‐regional failure rate of 12% at 10 years, despite receiving inferior systemic treatment by current standards. Local‐regional control after post‐mastectomy radiotherapy for pT3N0 breast cancers was excellent. Further research is needed to define post‐mastectomy radiotherapy indications for this patient population when receiving chemotherapy and endocrine therapy in line with current guidelines.