Effect of Time Interval between Breast-Conserving Surgery and Radiation Therapy on Outcomes of Node-Positive Breast Cancer Patients Treated with Adjuvant Doxorubicin/Cyclophosphamide Followed by Taxane

PURPOSE: This study evaluated the effect of surgery-radiotherapy interval (SRI) on outcomes in patients treated with adjuvant radiotherapy (RT) after breast-conserving surgery (BCS) and adjuvant four cycles of doxorubicin/cyclophosphamide (AC) followed by four cycles of taxane. MATERIALS AND METHODS: From 1999 to 2007, 397 eligible patients were diagnosed. The effect of SRI on outcomes was analyzed using a Cox proportional hazards model, and a maximal chi-square method was used to identify optimal cut-off value of SRI for each outcome. RESULTS: The median SRI was 6.7 months (range, 5.6 to 10.3 months). A SRI of 7 months was the significant cut-off value for distant metastasis-free survival (DMFS) and disease-free survival (DFS) using a maximal chi-square method. For overall survival, a significant cut-off value was not found. The patients with SRI > 7 months had worse 6-year DMFS and DFS than those with SRI ≤ 7 months on univariate analysis (DMFS, 81% vs. 91%, p=0.003; DFS, 78% vs. 89%, p=0.002). On multivariate analysis, SRI > 7 months did not affect DMFS and DFS. CONCLUSION: RT delayed for more than 7 months after BCS and adjuvant four cycles of AC followed by four cycles of taxane did not compromise clinical outcomes.