Researchers of a phase 3 randomized trial worked to provide data on the omission of irradiation in women who were at least 65 years of age with hormone receptor–positive, node-negative, T1 or T2 primary breast cancer (tumors ≤3 cm in the largest dimension) who had been given treatment of breast-conserving surgery with clear excision margins and adjuvant endocrine treatment. The researchers randomly assigned women to be given either whole-breast irradiation (n=658) or no irradiation (n=668) with a median follow up of 9.1 years. Within 10 years, the cumulative incidence of the recurrence of local breast cancer was 9.5% (95% confidence interval [CI], 6.8 to 12.3) in the group without radiotherapy and 0.9% (95% CI, 0.1 to 1.7) in the group with radiotherapy. At 10 years, the overall survival was nearly the same in both groups with 80.8% (95% CI, 77.2 to 84.3) survival in the no radiotherapy group and 80.7% (95% CI, 76.9 to 84.3) survival in the radiotherapy group. There was no significant difference in the prevalence of regional recurrence and breast cancer-specific survival among the groups.

Reference: Kunkler IA, Williams LJ, Jack WJL, Cameron DA, Dixon JM. Breast-Conserving Surgery with or without Irradiation in Early Breast Cancer. N Engl J Med. 2023;388:585-594. doi:10.1056/NEJMoa2207586