Background: In breast cancer, a direct relationship exists between prognosis and the number of lymph nodes involved with metastatic disease. This study was undertaken to determine whether metastatic disease confined to the sentinel lymph nodes (SLN) has better prognosis than metastatic disease spread to non-SLNs, regardless of the number of nodes involved. Methods: The study group consisted of 449 breast cancer patients with positive axillary SLN who underwent regional nodal dissection. Cox proportional-hazard regression models were used to assess the association of the number of positive SLNs and non-SLNs with overall survival (OS) and disease-free survival (DFS). Results: In patients with disease confined to the SLNs, as the number of positive SLNs increased the OS and DFS remained the same. Once disease was present beyond the SLN, both DFS and OS were negatively impacted. On multivariate analysis non-SLN status remained an independent predictor of OS. A direct comparison was performed on the subset of patients with two positive lymph nodes. Group 1 had all disease confined to the SLNs (two positive SLNs), and group 2 had non-SLN disease (one positive SLN and one positive non-SLN). Despite an identical number of positive nodes, the OS rates were significantly worse in the group with disease present in a non-SLN (P = 0.004). Conclusion: The number of nodes involved with metastatic disease does not impact OS and DFS if all disease is confined to the SLNs. Non-SLN involvement negatively influences OS and DFS independent of the number of positive nodes.
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