Purpose: Postoperative breast irradiation is considered standard after breast-preserving surgery for cancer. We evaluated the efficacy of radiation therapy in the prevention of local recurrence in a patient population that had small-size breast cancer with features that suggested low biologic aggressiveness.
Patients and methods: Women (n = 264) older than 40 years who were treated by breast resection with > or = 1 cm of tumor-free margin and axillary nodal dissection were randomly assigned to receive or not to receive breast irradiation (cumulative dose, 50 Gy) after surgery. The tumor was required to be < or = 20 mm, node negative, progesterone receptor positive, well to moderately well differentiated and unifocal, and of low cell proliferation rate (ie, S phase fraction < or = 7% or nuclear Ki-67 expression < 10%) and had to lack an extensive intraductal component. The median follow-up time was 12.1 years after random assignment.
Results: Sixteen (11.6%) and 34 (27.2%) cancers recurred locally in the radiotherapy and the control arms, respectively (P = .0013). Time to local recurrence was longer in the radiotherapy arm (hazard ratio [HR], 0.36; 95% CI, 0.20 to 0.65; P = .00071). Twenty-one patients assigned to radiotherapy and 26 assigned to control died during the follow-up. There were no differences in overall survival time (HR, 0.63; 95% CI, 0.35 to 1.12; P = .11), distant disease-free survival (P = .94), or breast cancer-specific survival (P = .56) between the radiation therapy and control groups.
Conclusion: Radiation therapy after breast resection reduces the frequency of ipsilateral breast recurrences, even among women with small-size breast cancers that have favorable histologic features and that are resected with at least a 1-cm margin. Postoperative radiotherapy did not significantly improve survival.