Clinical Significance of Extracapsular Invasion at Sentinel Lymph Nodes in Breast Cancer Patients with Sentinel Lymph Node Involvement

Abstract

Background: A certain number of patients have extracapsular invasion (ECI) at the sentinel lymph node (SLN), but only a few reports describe its clinical significance. This study aimed to determine the clinical significance of ECI at SLN in breast cancer patients with involved SLN. Methods: This study evaluated ECI at SLN in 131 consecutive SLN-positive patients who underwent axillary lymph node dissection between 2003 and 2008 at the National Kyushu Cancer Center with regard to their long-term prognosis and non-SLN metastasis. Results: Of the 131 patients, 46 (35 %) tested positive for ECI at SLN. Of these 46 patients, 61 % (28/46) had non-SLN metastasis compared with 28 % (24/85) in ECI-negative group (χ2 test; P < 0.001). Multivariate analysis showed that ECI at SLN is significantly predictive for non-SLN metastasis [hazard ratio (HR) 3.2; 95 % confidence interval (CI) 1.4–7.1; P = 0.005]. The 5-year recurrence-free survival (RFS) rates were 71.3 % in the ECI-positive group and 89.9 %in the ECI-negative group (P = 0.001, log-rank test). Cox-regression analysis showed that ECI at SLN independently predicts lower RFS (HR 4.5; 95 % CI 1.8–11.7; P = 0.002). Conclusions: The findings show that ECI at SLN is an independent predictor of both non-SLN metastasis and poor prognosis for breast cancer patients with involved SLN. The clinical significance of ECI at SLN in operable-stage breast cancer warrants further study.