Long-term outcomes of adjuvant radiation in elderly Asians with early stage IIA breast cancer after breast-conserving surgery: a population-based study

The benefit of postoperative radiotherapy (RT) for Asian older patients with early-stage breast cancer remains unclear. This study aimed to investigate the use of adjuvant RT in clinical practice to treat elderly Asians by evaluating relevant clinical factors. A total of 1,180 older adults with American Joint Committee on Cancer stage T2N0 breast cancer with tumors ≤ 3 cm were enrolled from the Taiwan Cancer Registry between January 2011 and December 2020. We used multivariable Cox proportional hazards models to control for clinical factors and propensity score matching for sensitivity analysis. Overall survival (OS) and recurrence-free survival (RFS) were estimated using the Kaplan–Meier method and the log-rank test. Among the patients aged > 70 years who received hormone therapy, RFS differed significantly between those who received adjuvant RT and those who did not (hazard ratio [HR] = 0.115, p = 0.01). The 5-year OS rate was 93% and 76% for those with and without adjuvant RT, respectively (HR = 0.34, 95% confidence interval [CI], 0.26–0.46, p < 0.001). After covariate adjustment, the OS advantage from RT was significant both for patients aged 65–70 years (HR = 0.284, 95% CI, 0.155–0.520) and those aged > 70 years (HR = 0.512, 95% CI, 0.358–0.734). RFS was significantly improved by adjuvant RT in patients aged > 70 years with hormone-positive tumors. Furthermore, OS advantage was observed in Asian older adults with early breast cancer who received RT following conservative breast surgery. Adding RT to adjuvant systemic therapy is beneficial and well-tolerable in older Asian patients with small T2 tumors.