Intraoperative prediction of non‑sentinel lymph node metastases in breast cancer using cytokeratin 19 mRNA copy number: A retrospective analysis

Abstract : One‑step nucleic acid amplification (OSNA) is a molecular procedure used intraoperatively for the detection of sentinel lymph node (SLN) metastases. The aim of the present study was to define a cut‑off of cytokeratin (CK)19 mRNA copy number predictive of positive completion axillary lymph node dissection (ALND). The OSNA procedure was employed for SLN analysis in 812 patients with T1‑T2 N0 breast cancer. A total of 197 patients with SLN metastases were retrospectively analyzed. A total of 40 patients (20%) had non‑SLN metastases. Receiver operating characteristics curve analysis established a cut‑off of 5,000 CK19 mRNA copy number with 75% sensitivity and 72% specificity. The positive and negative predictive values were 40.5 and 92%, respectively. Multivariate analysis showed that this cut‑off and tumor localization in the outer or lower‑outer quadrant of the breast were significantly associated with non‑SNL involvement (P<0.001 and P=0.025, respectively). The findings of the present study support the conventional cut‑off of 5,000 copies for intraoperative decision to perform ALND, whereas ALND can safely be avoided in patients with tumor located outside the outer or lower‑outer quadrant of the breast if the CK19 mRNA copy number is <5,000.