3677 - Long Term Outcomes of Adjuvant Radiation in Early-Stage Breast Cancer Women with 65 Years or Older after Breast-Conserving Surgery

S. M. Lin¹, H. Y. Ku², T. W. Liu², and H. J. Chang²; ¹Chang Gung Memorial Hospital, Taoyuan 333, Taiwan, ²National Health Research Institute, Miaoli 350, Taiwan

Purpose/Objective(s): The benefit of postoperative radiotherapy for early-stage breast cancer in elderly Asian population remains unclear. This study aimed to investigate the role of adjuvant radiotherapy in early-stage breast cancer considering various clinical factors including age. Materials/

Methods: A total of 1202 patients diagnosed with AJCC stage I-IIA breast cancer and tumor less than 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. The overall survival (OS) and recurrence-free survival (RFS) were estimated with the Kaplan–Meier method and log rank test method.
Results: After covariate adjustment, OS and RFS did improve significantly in patients over 70 years old receiving adjuvant hormone therapy and radiotherapy. The 5-year OS rates were 93% and 73% for those with and without adjuvant radiotherapy, respectively (hazard ratio [HR] = 0.50, 95%CI=0.32-0.79, p<0.001). For hormone-negative early breast cancer, the benefit of adjuvant radiotherapy to OS for patients with age more than 70 was not observed; while RFS was improved significantly (HR = 0.047, 95% CI= 0.01-0.32, p<0.001).
Conclusion: Adjuvant radiotherapy did improve the clinical outcomes of elderly patients with early breast cancer in Asia irrespective of hormone status. The results should be further clarified in larger population.