Validation of international predictive nomograms for non-sentinel lymph node metastases in Hong Kong breast cancer patients with positive sentinel lymph nodes

Background: Management of the axilla in breast cancer patients has been evolving over the past decade with progressive de-escalation in axillary surgery. In this study, we investigated the factors predicting non -sentinel lymph node (NSLN) metastases in sentinel lymph node (SLN) positive breast cancer patients in Hong Kong and assessed international predictive scoring systems [Memorial Sloan Kettering Cancer Center (MSKCC), MD Anderson Cancer Center (MDACC), Tenon score] for their accuracy and applicability in our locality.<br /> Methods: This is a retrospective study of 126 breast cancer patients who received completion axillary dissection after a positive SLN biopsy (SLNB) between April 2011 and April 2019. Their MSKCC, MDACC and Tenon predictive scores for NSLN metastases were compared with receiver operating characteristic (ROC) analysis. Multivariate logistic regression was performed to identify independent predictors of non -sentinel node metastases.<br /> Results: The majority had early disease, with only 7.1% (9 patients) having T3 disease. Only 35 patients (27.8%) had positive NSLN after axillary dissection. The area under the ROC curve (AUROC) of MDACC (0.708, 95% CI: 0.583-0.833) was the highest, followed by MSKCC (0.674, 95% CI: 0.553-0.795) and Tenon (0.660, 95% CI: 0.531-0.789). The AUROC improved after excluding patients with micrometastases only on SLNB. All three normograms showed poorer performance when there was only one positive SLN. Multivariate analysis found grade (OR: 0.107, 95% CI: 0.14-0.801, P=0.03), ratio of positive to negative SLN (OR: 0.005, 95% CI: 0.001-0.639, P=0.033) and extranodal spread (OR: 2.754, 95% CI: 0.979-7.745, P<0.05) as significant independent predictors of NSLN metastases.<br /> Conclusions: MSKCC, MDACC and Tenon scores all show acceptable accuracy in predicting NSLN metastases but are less accurate in patients with only one positive SLN or micrometastases. MDACC shows the best accuracy in our subset of patients in Hong Kong.