Ratio and log odds of positive lymph nodes in breast cancer patients with mastectomy

• We examine prognostic role of nodal indices in breast cancer patients.
• Ratio-based nodal indices are better than traditional number of positive lymph nodes.
• Lymph node ratio is best when sufficient number of lymph nodes is harvested.
• Log odds index shows superior prediction if limited lymph nodes harvest occurs.

PurposeThis study aimed to investigate the predictive role of lymph nodes (LNs) and assess the prognostic significance of the ratio of positive LNs (LNR) and log odds of positive LNs (LODDS) in breast cancer patients who have undergone a mastectomy.Patients and methodsAll of the breast cancer patients in the Taiwan Cancer Database during 2002–2006 were considered. We excluded patients who had inflammatory breast cancer, stage 0 and IV disease, breast conservative surgery or survival <1 month. The primary end point was overall survival (OS). A Cox hazards model was constructed and compared via Nagelkerke R2 (R2N) and receiver operating characteristics (ROC).ResultsA total of 11,349 (6042 node-negative, 5307 node-positive) patients were enrolled, and 10.5% patients had a limited number of LNs harvested. In a multivariate Cox model, LNR and LODDS demonstrated prognostic significance (<0.001). For node-positive patients, a model with LNR showed the best fit (P < 0.001; R2N = 18.2%) when sufficient LNs were examined. However, a model with LODDS showed the best fit in patients with a limited number of LNs harvested (P < 0.001; R2N = 21.1%), even in node-negative patients (P = 0.004; R2N = 13.5%). The area under the ROC curve (AUC) was highest for LODDS (AUC: 0.761), followed by LNR (AUC: 0.757). A limited LN harvest induced an AUC value for an approximate 3.6% loss (LNR) or 3.1% loss (LODDS).ConclusionThe prognostic superiority of LNR is confounded by a limited LN harvest, thus making LODDS the most powerful and unified prognostic classifier in breast cancer patients who have had a mastectomy.