Timing of radiotherapy following breast-conserving surgery: outcome of 1393 patients at a single institution

The role of postoperative radiotherapy in breast-conserving therapy is undisputed. However, optimal timing of adjuvant radiotherapy is an issue of ongoing debate. This retrospective clinical cohort study was performed to investigate the impact of a delay in surgery-radiotherapy intervals on local control and overall survival. Data from an unselected cohort of 1393 patients treated at a single institution over a 17-year period (1990-2006) were analyzed. Patients were assigned to two groups (CT+/CT-) according to chemotherapy status. A delay in the initiation of radiotherapy was defined as >7 weeks (CT- group) and >24 weeks (CT+ group). The 10-year regional recurrence-free survival for the CT- and CT+ groups were 95.6 and 86.0%, respectively. A significant increase in the median surgery-radiotherapy interval was observed over time (CT- patients: median of 5 weeks in 1990-1992 to a median of 6 weeks in 2005-2006; CT+ patients: median of 5 weeks in 1990-1992 to a median of 21 weeks in 2005-2006). There was no association between a delay in radiotherapy and an increased local recurrence rate (CT- group: p=0.990 for intervals 0-6 weeks vs. ≥7 weeks; CT+ group: p=0.644 for intervals 0-15 weeks vs. ≥24 weeks) or decreased overall survival (CT- group: p=0.386 for intervals 0-6 weeks vs. ≥7 weeks; CT+ group: p=0.305 for intervals 0-15 weeks vs. ≥24 weeks). In the present cohort, a delay of radiotherapy was not associated with decreased local control or overall survival in the two groups (CT-/CT+). However, in the absence of randomized evidence, delays in the initiation of radiotherapy should be avoided. (orig.)