Omitting irradiation after breast-conserving surgery increases incidence of local recurrence in women 65 years of age or older with low-risk, hormone receptor–positive early breast cancer, but has no detrimental effect on distant recurrence or overall survival, as shown by a study recently published on The New England Journal of Medicine.

This phase 3 randomized trial enrolled 1326 women who had hormone receptor–positive, node-negative primary breast cancer treated with breast-conserving surgery with clear excision margins and adjuvant endocrine therapy. Patients were randomly assigned to receive whole-breast irradiation or no irradiation; after a median follow-up of 9.1 years the cumulative incidence of local breast cancer recurrence within 10 years was 9.5% in the no-radiotherapy group and 0.9% in the radiotherapy group. The incidence of local recurrence up to 10 years among patients who received radiotherapy remained low, whereas that among patients who did not receive radiotherapy continued to increase with no apparent plateau. «However, the absolute difference in the incidence of local recurrence at 10 years was modest, 8.6 percentage points», authors say. «Despite this difference, irradiation had no substantial effect on the incidence of regional or distant metastases (1.6% in the no-radiotherapy group and 3% in the radiotherapy group) or on breast cancer–specific or overall survival at 10 years, almost identical in the two groups (80.8% with no radiotherapy and 80.7% with radiotherapy). This data provide robust evidence indicating that irradiation can be safely omitted in women 65 years of age or older who have grade 1 or 2, ER-high cancers treated by breast-conserving therapy, provided that they receive 5 years of adjuvant endocrine therapy», authors conclude.