After a median follow-up of 15 years, adjuvant radiotherapy significantly decreased the risk of 10y-IBTR as first event in luminal-A (from 19 to 9%; HR = 0.46; 95% CI = 0.29–0.74; p = 0.001) and luminal-B (non Her2 enriched; from 24 to 8%; HR = 0.33; 95% CI = 0.16–0.65; p = 0.001) phenotypes but not for Her2-enriched (from 15 to 19%; HR = 1.29; 95% CI = 0.38–4.40; p = 0.6), and triple negative BC patients (from 21 to 6%; HR = 0.25; 95% CI = 0.05–1.12; p = 0.08). This evidence concerns the gene ERBB2 and breast cancer.