One-step Nucleic Acid Amplification (OSNA): Intraoperative Rapid Molecular Diagnostic Method for the Detection of Sentinel Lymph Node Metastases in Breast Cancer Patients in Korean Cohort

Purpose: Sentinel lymph node (SLN) biopsy has become a standard procedure in breast cancer patient management. Accurate intraoperative assessment of metastasis of SLNs is essential for appropriate selection to avoid unnecessary axillary dissection. The aim of this study was to evaluate the performance of one-step nucleic acid amplification (OSNA) assay for detection of sentinel lymph node metastasis examination in breast cancer patients. Methods: In this study, we compared intraoperative OSNA to histological investigation with multi-level observation in 284 sentinel lymph nodes of 199 patients. Surgically obtained sentinel lymph nodes were sectioned into 2 mm intervals of up to four pieces, half of which were examined with the OSNA assay. The other half of adjacent pieces were histopathologically examined both intraoperatively and postoperatively. The presence/absence of metastases was judged by observing hematoxylin and eosin staining and cytokeratin (AE1/ AE3) immunohistochemically stained multiple slides from one lymph node. Results: Among 199 patients included, 36 cases were positive on histological examination and 34 cases were positive on OSNA assay. There were 14 discordant cases. The overall concordance with histology was 93.0% (95% confidence interval [CI], 0.86-0.96), with a sensitivity of 77.8% (95% CI, 0.61-0.90), specificity of 96.3% (95% CI, 0.92-0.99), positive predictive value of 82.4% (95% CI, 0.65-0.93) and negative predictive value of 95.2% (95% CI, 0.91-0.98). The kappa statistic analysis indicated substantial agreement of both methods, with a value of 0.76 (95% CI, 0.64-0.88). The average turnaround time was 39.0 minutes. Conclusion: The results of this study indicate that the OSNA assay has equivalent accuracy to histopathology in detecting breast cancer metastasis to lymph nodes when each method is assigned two alternate blocks of four blocks sectioned at 2 mm intervals.