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.