Postmastectomy radiotherapy is associated with a lower locoregional recurrence rate and improved disease-free and overall survival when combined with chemotherapy in premenopausal high-risk breast-cancer patients. However, whether the same benefits apply also in postmenopausal women treated with adjuvant tamoxifen for similar high-risk cancer is unclear. In a randomised trial among postmenopausal women who had undergone mastectomy, we compared adjuvant tamoxifen alone with tamoxifen plus postoperative radiotherapy.

Between 1982 and 1990, postmenopausal women with high-risk breast cancer (stage II or III) were randomly assigned adjuvant tamoxifen (30 mg daily for 1 year) alone (689) or with postoperative radiotherapy to the chest wall and regional lymph nodes (686). Median follow-up was 123 months. The endpoints were first site of recurrence (locoregional recurrence, distant metastases, or both), and disease-free and overall survival.

Locoregional recurrence occurred in 52 (8%) of the radiotherapy plus tamoxifen group and 242 (35%) of the tamoxifen only group (p<0.001). In total there were 321 (47%) and 411 (60%) recurrences, respectively. Disease-free survival was 36% in the radiotherapy plus tamoxifen group and 24% in the tamoxifen alone group (p<0.001). Overall survival was also higher in the radiotherapy group (385 vs 434 deaths; survival 45 vs 36% at 10 years, p=0.03).

Postoperative radiotherapy decreased the risk of locoregional recurrence and was associated with improved survival in high-risk postmenopausal breast-cancer patients after mastectomy and limited axillary dissection, with 1 year of adjuvant tamoxifen treatment. Improved survival in high-risk breast cancer can best be achieved by a strategy of both locoregional and systemic tumour control.