Validation of clinical prediction rules for a low probability of nonsentinel and extensive lymph node involvement in breast cancer patients

Background: Two recently developed clinical prediction rules aim to anticipate the lack of nonsentinel lymph node metastases and the involvement of less than 4 lymph nodes in breast cancer patients with positive sentinel lymph nodes (SLNs). Methods: The University of Louisville Breast SLN Study clinical prediction rules were validated on an independent set of SLN-positive patients with tumors ≤15 mm. Results: The data on 475 and 473 patients, respectively, were used for the validation. The areas under the receiver operating characteristic curves were similar to the originals for both predictive tools (.70 and .76). The lowest score of 1 identified 5 of 7 patients with disease limited to the SLNs and 161 of 165 as having less than 4 involved lymph nodes. Conclusions: A subset of patients with SLN-only involvement and less than 4 metastatic lymph nodes can probably be identified by means of the Louisville clinical prediction rules, but prediction of the lack of non-SLN metastasis seems less reliable.