Predicting possibility of positive non-sentinel nodes in sentinel node–positive breast cancer patients: A Singapore series.

51 Background: Sentinel lymph node (SLN) biopsy is an accepted method for determining the axillary status in early breast cancer patients. If positive, a standard axillary clearance is performed. However, recent studies have shown that many of these patients may not have additional positive non sentinel nodes, and the removal of these additional nodes may not be necessary or confer any benefit. We set out to identify factors that determine non sentinel node positivity and whether this could be predicted from our series of early breast cancer patients. Methods: We retrospectively reviewed 337 of our early breast cancer patients from 2005 to 2008 who had atleast one positive sentinel node and had undergone a full axillary clearance. Tumour factors and sentinel node variables were collected and compared between those patients with additional positive non sentinel nodes and those with no positive nodes in the axillary clearance. Results: Five factors were found on univariate analysis to be associated with non sentinel node positivity. They are ratio of positive SLN to total number of SLN, number of positive SLNs, size of metastasis in the SLN, tumour size and lymphovascular invasion. The first 3 factors were used to model a logistic-regression model which has good prediction ability to predict positivity of non SLNs (value under ROC curve 0.726 [95% CI 0.666-0.786]). Conclusions: Tumor factors and SLN variables are able to help us predict the possibilty of additional positive non SLN once at least a SLN is positive. This can help the surgeon and patient in the decision making process on the need for a full axillary clearance.