Risk Factors and a Predictive Nomogram for Non-Sentinel Lymph Node Metastases in Chinese Breast Cancer Patients with One or Two Sentinel Lymph Node Macrometastases and Mastectomy

Background: Two ongoing prospective randomized trials are evaluating whether omitting axillary lymph node dissection (alnd) in patients with breast cancer (bca) and sentinel lymph node (sln) macrometastases undergoing mastectomy is safe. Determining predictive risk factors for non-sln metastases and developing a model to predict the probability of those patients having non-sln metastases is also important. Methods: This retrospective study enrolled 396 patients with bca and 1–2 slns with macrometastases who underwent alnd and mastectomy between January 2012 and December 2016. Factors influencing the non-sln metastases were determined, and a predictive nomogram was formulated. Performance of the nomogram was evaluated by its area under the curve (auc). Results: We developed a predictive nomogram with an auc of 0.81 (cross-validation 95% confidence interval: 0.75 to 0.86) that included 4 factors (tumour size, histologic grade, and number of negative slns and axillary lymph nodes on imaging). Conclusions: Our predictive nomogram assesses the risk of non-sln metastases in patients with bca and 1–2 sln macrometastases undergoing mastectomy.