Long-term survival effect of the interval between mastectomy and radiotherapy in locally advanced breast cancer.

Introduction: The timing of postmastectomy radiotherapy (PMRT) may influence locoregional recurrence and survival outcomes. In this study, we assessed the long-term survival effect of the interval between surgery and PMRT in locally advanced breast cancer treated with mastectomy and adjuvant chemotherapy.

Methods: In this retrospective study, we included women with locally advanced breast cancer who underwent adjuvant chemotherapy and PMRT after mastectomy between 1999 and 2007. Based on the interval between surgery and PMRT, the patients were classified into three groups: Group 1 (≤4 vs >4 months), Group 2 (≤5 vs >5 months), and Group 3 (≤6 vs >6 months). Univariate and multivariate regression analyses were performed to determine the prognostic factors of survival outcomes.

Results: A total of 340 women were included in this study, and the median follow-up duration was 79.8 months. The median surgery-PMRT interval was 5 months. The surgery-PMRT interval including Group 1, Group 2, and Group 3 was not significantly associated with locoregional recurrence-free survival, distant metastasis-free survival, disease-free survival, and overall survival. In addition, in the subgroup analysis of the effect of surgery-PMRT interval on survival outcomes according to various clinicopathologic factors, the surgery-PMRT interval was also not associated with survival outcomes in different age groups, tumor stage, and breast cancer subtypes.

Conclusion: Our findings suggest that the delay in the start of PMRT in locally advanced breast cancer does not increase the likelihood of locoregional recurrence, distant metastasis, and death.