Biological Subtype Predicts Risk of Locoregional Recurrence After Mastectomy and Impact of Postmastectomy Radiation in a Large National Database

TN patients had the highest risk of LRR and the least benefit from PMRT; these patients may benefit from alternative treatment strategies. In contrast, in the era of HER2-directed therapy, the role of local therapy may need to be reassessed among HER2 patients.