Clinical relevance of the timing of radiotherapy after breast-conserving surgery Results of a large, single-centre, population-based cohort study

Purpose To investigate the effect of the timing of radiation therapy after breast-conserving surgery in relation to distant metastasis-free survival and disease-specific survival. Methods The analysis was performed in relation to 4189 women all undergoing breast-conserving therapy (BCT). Three groups were defined with respect to lymph node status and the use of adjuvant systemic therapy (AST). Patients were categorized into time intervals: < 37 days, 37-53 days, 54-112 days and > 112 days. Results For women without lymph node metastases and with favourable characteristics aged > 55 years, an improved treatment efficacy was noted when starting radiotherapy with a time interval of < 37 days. The same was observed for women with lymph nodes metastases receiving AST aged <= 50 years. Finally, for women aged > 50 years with negative lymph node status but with unfavourable characteristics and receiving AST, an improved treatment efficacy was noted when starting radiotherapy after a time interval of >= 37 days. Conclusion The results of our study further support the hypothesis that the timing of radiotherapy may have an impact on treatment efficacy and that further studies (preferably randomized trials) are indicated.