Abstract: Background and purpose: When patients have positive sentinel lymph node (SLN), axillary lymph node dissection (ALND) is usually performed, but most of them have no metastasis in the non-sentinel lymph node (nSLN). It is of great significance to predict metastasis of nSLN precisely. The aim of the study was to establish a nomogram for the intraoperative prediction of nSLN metastasis in breast cancer patients using one-step nucleic acid amplification (OSNA) techniques and to direct the subsequent therapy for breast cancer effectively. Methods: Of 552 breast cancer patients who underwent SLN biopsy in the 2010 OSNA clinical trial, 103 with SLN metastasis treated with ALND were assessed to establish a nomogram for intraoperative prediction of nSLN based on the molecular diagnosis. A validation cohort of 61 patients who met the similar criteria in the 2015 OSNA clinical trial subsequently validated it. Results: Primary tumor size, total tumor load, the number of positive SLNs and negative SLNs were associated with the presence of nSLN metastasis based on the multivariable logistic regression results, and a nomogram was established with these variables. Its area under the ROC curve was 0.814 for the predictive model and it was 0.842 in the re-validation cohort. The tumor size assessed by the postoperative histological examination was replaced by the size evaluated by the imaging examination, and the area under the ROC curve was 0.838. There was no statistically significant difference in the accuracy compared with the former validation data (P=0.740 6). Conclusion: The predictive nomogram based on the molecular diagnosis can predict the nSLN metastases intra/post-operatively. It appears to be obviously superior to other predictive models and may help to guide the axillary management and to make decisions about radiation target region.

Key words: Breast cancer, Sentinel lymph node, Molecular diagnostic techniques