Validation of the Louisville breast sentinel node prediction models and a proposed modification to guide management of the node positive axilla

Abstract

The ACOSOG Z11 trial is rapidly changing use of axillary dissection, but it is not known how generalizable the Z11 results are. This study compares characteristics of the Z11 patients with the larger group of sentinel node-positive patients and evaluates two previously described Louisville algorithms to determine whether they might still be useful to predict extent of axillary node involvement and guide management of the axilla. The Yale Breast Center database was queried to calculate the Louisville prediction points for patients with a positive sentinel node and to compare the predicted with actual results. Of 1215 sentinel node biopsies performed between 2004 and 2010, 282 (23%) had at least one positive node. Thirty-one per cent of these patients would have been eligible for Z11. This group had much less axillary node involvement than the 69 per cent who were ineligible. The Yale data confirmed the accuracy of the two Louisville models and showed that tumor size, number of positive sentinel nodes, and proportion of positive sentinel nodes were all significant predictors. However, these results were much more robust if at least three sentinel nodes had been removed. The Z11 patients were clearly a good risk group. The data validate the two Louisville models and suggest that the models may be useful to select patients to avoid axillary dissection, both among the currently Z11-eligible and -ineligible populations. A modified algorithm is proposed in which all patients with a positive sentinel node have at least three total nodes removed.