The Performance of the One Step Nucleic acid Amplification (OSNA) Assay in Breast Cancer Patients with Receiving Preoperative Systemic Therapy.

Background: The OSNA (One Step Nucleic acid Amplification) assay is a semi-automated lymph node examination method using molecular biological technique. The OSNA assay has been validated for breast cancer patients without receiving preoperative systemic therapy (PST) by several clinical studies and has currently become more popular as sentinel lymph node (SLN) examination method with the following two main advantages; 1) to allow examination of the whole portion of a node, 2) to allow intraoperative judgment of metastasis positive or negative. However, the feasibility of the OSNA assay in breast cancer patients treated by PST has never been confirmed. In this multi-central clinical study, we compared the judgments of the OSNA assay and of pathological examination on lymph nodes dissected after receiving PST to evaluate the performance of the OSNA assay. Material & Methods: Three hundred two nodes dissected from the 80 breast cancer patients who received PST were examined. Each lymph node was divided at 2mm intervals and the slices were alternately applied to the OSNA assay and pathological examination with H&E staining and CK19 immunohistochemical staining of permanent-section. In pathological examination, judgments of metastasis positive or negative were determined by one central-review pathologist according to the criteria of AJCC 7th edition ("positive" if >0.2mm metastases were detected). Result: The overall concordance rate between the OSNA assay and pathological examination was 91.1% (275/302) with sensitivity of 88.3% (53/60) and specificity of 91.7% (222/242) (Table). These results are very similar to those of the Japanese clinical validation study in breast cancer patients without receiving PST which was conducted by the almost same protocol (Tamaki Y, et al. Clin Cancer Res, 2009, 15: 2879-2884). Conclusion & Discussion: These results indicate the OSNA assay can be applicable for breast cancer patients after receiving PST as well as breast cancer patients without receiving PST. The OSNA assay will enable to examine the whole portion of nodes, leading to more detection of metastases (especially micrometastases) and more exact nodal staging for breast cancer patients treated by PST. Also, for the patients who receive sentinel lymph node biopsy after PST, the OSNA assay will be useful as intraoperative examination method of SLNs because it is expected to provide more correct judgments than current intraoperative methods such as frozen-section or touch-print cytology. [ABSTRACT FROM AUTHOR]