Routine Clinical Use of the One-Step Nucleic Acid Amplification Assay for Detection of Sentinel Lymph Node Metastases in Breast Cancer Patients: Results of a Multicenter Study in Japan

The objective of this study was to confirm, by means of a multicenter study conducted in Japan, the reliability and usefulness of the one-step nucleic acid amplification (OSNA) assay in routine clinical use for sentinel lymph node biopsy (SLNB) of breast cancer patients. Patients with Tis-T2N0M0 breast cancer who underwent SLNB before systemic chemotherapy comprised the study cohort. A whole sentinel lymph node (SLN) was examined intraoperatively with the OSNA assay except for a 1-mm-thick, central slice of the lymph node, which underwent pathologic examination after the operation. For patients who underwent axillary dissection, non-SLNs were examined with routine pathologic examination. In total, 417 SLNBs from 413 patients were analyzed. SLN metastases were detected with greater sensitivity by the OSNA assay than by pathologic examination (22.5% vs 15.8%; P < .001), as expected from the difference in size of the specimens examined. Patients who had SLN metastases assessed with the OSNA assay proved to harbor non-SLN metastases with an overall risk ratio of 33.7%. The risk of non-SLN metastasis was significantly lower for patients who had positive SLNs assessed as OSNA+ than for those who had SLNs assessed as OSNA++ (17.6% vs 44%; P = .012). The OSNA assay can be used for routine clinical SLNB, and its assessment for volume of metastasis may be a powerful predictive factor for non-SLN metastasis. Further studies with more patients are needed to confirm the usefulness of this assay for selection in the clinical setting of patients who do not need axillary dissection.