Is Postmastectomy Radiation Therapy Indicated in Patients with Close or Positive Margins?

Background: The indications for Post Mastectomy Radiation Therapy (PMRT) for positive or close margins are unclear. We examined the indications for PMRT in mastectomy patients with close or positive margins and determined patterns for relapse and survival. Methods: The pathology reports of 610 patients treated with a mastectomy from 1999-2012 were reviewed. Of these, 72 patients had a positive or <2 mm margin. Demographic, tumor characteristics, treatments and survival were compared between women treated with and without PMRT. Results: The mean follow up was 4.1 years. Patients who received PMRT were younger (p = 0.03) and more likely to receive chemotherapy (p = 0.03). Patients with lymphovascular invasion (LVI) were more likely to undergo PMRT (p = 0.02). Seven patients who did not receive PMRT recurred. There was no correlation with locoregional failure. The disease free survival was better in the PMRT group (p = 0.03), but the overall survival was the same. Conclusion: We found that women with a close or positive margin who were younger, had LVI, and who received chemotherapy received PMRT. The disease free survival was better in the PMRT cohort, but the overall survival was similar. Long-term follow up of patients is warranted to see if PMRT offers a survival advantage.