Large Tumor Size is an Indicator for the Timely Administration of Adjuvant Radiotherapy in Luminal Breast Cancer with Positive Lymph Node

PURPOSE: The optimum timing of adjuvant radiotherapy for breast cancer patients who had undergone surgery remains unclear. The present study aimed to identify the clinical factors which could assist the selecting of time interval (TI) between surgery and adjuvant radiotherapy in luminal breast cancer with lymph node metastasis. PATIENTS AND METHODS: This retrospective study included 1054 luminal breast cancer patients with lymph node metastasis, diagnosed between May 2004 and December 2014, and treated with surgery followed by adjuvant therapy. Overall survival (OS) and disease-free survival (DFS) were compared between patients in the short and long TI groups. Multivariate analysis was performed to examine clinical factors associated with DFS. Subgroups analysis was further performed based on the significant predictors of DFS to explore the association of TI and tumor prognosis. RESULTS: For the whole group of patients, there was no difference in OS and DFS between patients with long and short TI. Multivariate analysis showed that age, N stage and tumor size were significant predictors of DFS. Subgroup analysis demonstrated that neither age nor N stage were informative in TI selection; in contrast, in patients with large tumors, a short TI was associated with better DFS than a long TI. In patients with small tumors, there was no significant association between TI and tumor prognosis. In the multivariable analysis, TI was independent predictor of DFS and local recurrence-free survival in patients with large tumors. CONCLUSION: Large tumor size is an indicator for the timely administration of adjuvant radiotherapy in luminal breast cancer with positive lymph node.