Patients who were ER/PR positive but did not receive hormone therapy were 14%, 41% and 65% less likely to receive radiation after BCS in stage I (RR = 0.86; 95% CI: 0.83, 0.89), II (RR = 0.59; 95% CI: 0.49, 0.68), and III (RR = 0.35; 95% CI: 0.16, 0.60) cancers, respectively, than those who were ER/PR positive and received hormone therapy. The gene discussed is ESR1; the disease is cancer.