Risk factors for locoregional recurrence after postmastectomy radiotherapy in breast cancer patients with four or more positive axillary lymph nodes

Background We investigated risk factors for locoregional recurrence (LRR) in breast cancer patients with 4 or more positive axillary lymph nodes receiving postmastectomy radiotherapy (PMRT). Methods Medical records (1998-2007) were retrospectively reviewed for the population of interest. The Kaplan-Meier method was used to calculate the survival rate; Cox regression models were used for univariate and multivariate analysis of predictors of breast cancer LRR. Results The study enrolled 439 patients. Median duration of follow-up was 54 months. The 5-year rates of locoregional recurrence-free survival (LRRFS), distant metastasis-free survival (DMFS), and breast cancer-specific survival (BCSS) were 87.8%, 59.5%, and 70.7% respectively. In patients with LRR and no concomitant metastasis, and in those without LRR, the 5-year rates of DMFS were 21.1% and 65.7% respectively (p < 0.001), and the 5-year rates of BCSS were 34.5% and 76.4% respectively (p < 0.001). Univariate analysis showed that menopausal status (p = 0.041), pN stage (p = 0.006), and positivity for HER2 [human epidermal growth factor receptor 2 (p = 0.003)] or the triple-negative disease subtype (p < 0.001) were determinants of LRRFS. Multivariate analysis showed that pN3 stage [hazard ratio (HR): 2.241; 95% confidence interval (CI): 1.270 to 3.957; p = 0.005], HER2 positivity (HR: 2.705; 95% CI: 1.371 to 5.335; p = 0.004), and triple-negative disease subtype (HR: 4.617; 95% CI: 2.192 to 9.723; p < 0.001) were independent prognostic factors of LRRFS. Conclusions In breast cancer patients with 4 or more positive axillary lymph nodes who undergo PMRT for breast cancer, LRR significantly influences survival. Patients who developed LRR carried a high risk for distant metastasis and death. Pathologic stage (pN3), HER2 positivity, and the triple-negative disease subtype are risk factors that significantly influence LRRFS.