Impact of postmastectomy radiation therapy in T1-2 breast cancer patients with 1-3 positive axillary lymph nodes

The effect of postmastectomy radiotherapy (PMRT) on T1-2 breast cancer patients with 1-3 positive axillary lymph nodes is controversial up to now. The purpose of this study was to evaluate the impact of postmastectomy radiotherapy for these patients. The prognostic factor effecting locoregional free-survival (LRFS) was also analyzed. In the retrospective clinical data of 1674 eligible patients, survival analysis was performed using the method of Kaplan-Meier and the log-rank test. Cox regression analysis was applied to identify the significant prognostic factors. We found PMRT increased 5-year LRFS (p=0.003), but could not improve 5-year disease-free survival or overall survival statistically. For patients without PMRT, multivariate analysis revealed that age, lymph node ratio and molecule subtype were risk factors effecting LRFS. To further analyze the role of PMRT, we grouped all the patients into low risk group (0 or 1 risk factor) and high risk group (2 or 3 risk factors) depending on these risk factors. We found that in low-risk group, PMRT increased only 5-year LRFS (p=0.012). However, in high-risk group, PMRT increased both 5-year LRFS (p=0.005) and 5-year disease-free survival (p=0.033), but could not improve 5-year overall survival statistically. Thus, these data provide the evidence that PMRT could improve LRFS for T1-2 breast cancer patients with 1-3 positive axillary lymph nodes. Additionally, PMRT could improve LRFS and disease-free survival for high risk patients. Age, lymph node ratio and molecule subtype were high risk factors effecting LRFS in our study.