Impact of delayed radiotherapy on local control in node-negative breast cancer patients treated with breast-conserving surgery and adjuvant radiotherapy without chemotherapy

Abstract

Aim and background To evaluate the effect of the surgery-radiotherapy interval (SRI) on local control in node-negative breast cancer patients treated with breast-conserving surgery and adjuvant radiotherapy without chemotherapy. Methods From February 1992 to January 2002, 171 patients with node-negative breast cancer underwent breast-conserving surgery and adjuvant radiotherapy without chemotherapy. The whole breast was irradiated up to 50.4 Gy in 28 fractions followed by a 10-Gy boost to the tumor bed. Forty-four patients received tamoxifen in addition to radiotherapy. Patients were divided into 2 groups according to the length of SRI: <6 weeks (128 patients) versus ≥6 weeks (43 patients). The median follow-up period was 87 months (range, 22–167). Results The 8-year local control rates of patients with SRI <6 weeks and ≥6 weeks were 94.5% and 92.7%, respectively (P = 0.1140). When age, tumor size, resection margin status, combination with hormonal therapy, and SRI were incorporated into the Cox proportional hazards model, SRI <6 weeks and age at diagnosis ≥40 years were associated with increased local control (P = 0.0343 and 0.0264, respectively). In the subgroup analysis, SRI <6 weeks was correlated with a higher local control rate for patients aged <40 years (P = 0.0142). Among older patients, however, there was no statistical difference in local control according to SRI (P = 0.6655). Treatment interval had no impact on overall and distant metastasis-free survival. Conclusions Early radiotherapy within 6 weeks of breast-conserving surgery is associated with increased local control in patients with node-negative breast cancer not undergoing chemotherapy.