Impact of a higher radiation dose on local control and survival in breast-conserving therapy of early breast cancer: 10-year results of the randomized boost versus no boost EORTC 22881-10882 trial.

PURPOSE: To investigate the long-term impact of a boost radiation dose of 16 Gy on local control, fibrosis, and overall survival for patients with stage I and II breast cancer who underwent breast-conserving therapy. PATIENTS AND METHODS: A total of 5,318 patients with microscopically complete excision followed by whole-breast irradiation of 50 Gy were randomly assigned to receive either a boost dose of 16 Gy (2,661 patients) or no boost dose (2,657 patients), with a median follow-up of 10.8 years. RESULTS: The median age was 55 years. Local recurrence was reported as the first treatment failure in 278 patients with no boost versus 165 patients with boost; at 10 years, the cumulative incidence of local recurrence was 10.2% versus 6.2% for the no boost and the boost group, respectively (P < .0001). The hazard ratio of local recurrence was 0.59 (0.46 to 0.76) in favor of the boost, with no statistically significant interaction per age group. The absolute risk reduction at 10 years per age group was the largest in patients