In early stage breast cancer, radiotherapy is an integral part of locoregional treatment with breast-conserving surgery. However, few older patients are included in the clinical trials upon which these recommendations are based. Therefore, we performed a systematic review and meta-analysis to evaluate outcomes of radiotherapy after breast-conserving surgery in older patients.

A systematic search of PubMed and Embase was undertaken. Inclusion was restricted to randomized controlled trials in postmenopausal breast cancer patients. Pooled odds ratios were calculated for locoregional recurrence, distant recurrence, and overall survival.

We included 5 randomized clinical trials comprising 3,190 patients. Overall, 39 % of the patients were ≥ 70 years old, and most had hormone receptor-positive T1 tumors without nodal involvement. All patients received adjuvant systemic therapy. Patients who received radiotherapy had a lower relative risk of locoregional recurrence (pooled odds ratio [OR] 0.36; 95 % confidence interval [CI] 0.25-0.50). The 5-year absolute risk was 2.2 % (95 % CI 1.6-3.1) among patients who received radiotherapy, versus 6.5 % (95 % CI 5.3-7.9) among patients who did not. The absolute risk difference was 4.3 % (95 % CI 2.9-5.7), corresponding with a number needed to treat of 24. No differences were observed for distant recurrence or overall survival.

Although patients who received radiotherapy had a lower relative risk of locoregional recurrence, the absolute risk was low, and overall survival was not affected. We propose that the debate should not only focus on the relative risk but also on the absolute benefit of radiotherapy and the number needed to treat. Both treatment options may be reasonable in clinical practice.