Factors that predict the burden of axillary disease in breast cancer patients with a positive sentinel node

This study identifies clinical and pathologic factors predictive of having > or =4 involved axillary lymph nodes in breast cancer patients with a positive sentinel node. These factors may influence radiation therapy decisions. We reviewed the records of 201 patients with positive SLN who underwent axillary dissection; 34 of these patients had > or =4 positive axillary lymph nodes. Factors associated with > or = 4 lymph nodes were evaluated by chi(2) test, and multivariate logistic regression model was used to identify independent factors. On univariate analysis, presence of lymphovascular space invasion, extracapsular extension, increased number of positive SLN, increased size of tumor, macrometastases within the SLN, and decreased number of negative SLN were all significantly associated with having > or = 4 involved axillary lymph nodes. On multivariate analysis, presence of extracapsular extension (odds ratio [OR] = 3.76, P = 0.004), increased number of positive SLN (OR = 3.99, P = 0.006), increased size of tumor (OR = 3.33, P = 0.011 for size of 2.1 to 5 cm and OR = 8.28, P = 0.018 for size >5 cm), and decreased number of negative SLN (OR = 2.62, P = 0.037) were found to be significant. We have identified primary tumor and SLN variables that predict for a greater probability of having a significant burden of residual disease in the axilla that may affect treatment recommendations.