Prognostic Significance of Tumor-Positive Internal Mammary Sentinel Lymph Nodes in Breast Cancer : A Multicenter Cohort Study

INTRODUCTION: The introduction of the sentinel lymph node biopsy (SLNB) in breast cancer has renewed interest in lymphatic drainage to the internal mammary (IM) nodes. The clinical impact of tumor positive IM nodes is not completely clear. This study evaluated the incidence and impact on overall survival of metastatic IM SLNs. METHODS: Between 1997 and 2010, 3685 patients underwent surgery including SLNB for primary breast cancer following an intratumoral or peritumoral radioactive-tracer injection. The presence of lymph node metastases was categorized according to the TNM-classification. Cumulative overall survival was estimated and the influence of metastases in the IM nodes and other factors was assessed by Cox-regression-analysis. RESULTS: In 754 patients (20.5 %) ipsilateral IM lymph nodes were visualized on preoperative lymphoscintigraphy, retrieval rate of IM SLNs was 81.0 %. IM metastases were detected in 130 patients (21.3 % of retrieved SLNs and 3.5 % of all patients respectively). The presence of IM metastases was associated with axillary metastases (p < 0.001). After a median follow-up of 61.2 months, 10.9 % of patients had died. In a multivariate analysis IM metastases did not have a significant effect on overall survival [HR] 1.20; CI: 0.73-1.98. In patients without axillary metastases (n = 2398), the presence of IM metastases (n = 43) was associated with worse survival [HR] 2.68; 95 % CI: 1.30-5.54. CONCLUSION: Overall, the presence of IM metastases did not effect overall survival independent of other prognostic factors including axillary metastases. However, the small subgroup of patients who had IM metastases alone had worse outcome than patients without any regional lymph node metastases