Whole sentinel lymph node analysis by a molecular assay predicts axillary node status in breast cancer

BACKGROUND: The one-step nucleic acid amplification (OSNA) assay is a rapid procedure for the detection of lymph node (LN) metastases using molecular biological techniques. The aim of this study was to assess the reliability of the whole sentinel lymph node (SLN) analysis by the OSNA assay as a predictor of non-SLN metastases. METHODS: Consecutive 742 patients with breast cancer were enroled in the study. The association of non-SLN or ⩾4 LN metastases with clinicopathological variables was investigated using multivariate logistic analysis. RESULTS: In total, 130 patients with a positive SLN who underwent complete axillary LN dissection were investigated. The frequency of non-SLN metastases in patients who were OSNA+ and ++ was 19.3% and 53.4%, respectively, and that in patients with ⩾4 LN metastases who were OSNA+ and ++ was 7.0% and 27.4%, respectively. The cytokeratin 19 (CK19) mRNA copy number (⩾5.0 × 10(3); OSNA++) in the SLN was the most significant predictors of non-SLN metastases (P=0.003). The CK19 mRNA copy number (⩾1.0 × 10(5)) in the SLN was the only independent predictor of ⩾4 LN metastases (P=0.014). CONCLUSION: Whole SLN analysis using the OSNA assay could become a valuable method for predicting non-SLN and ⩾4 LN metastases.