[A novel diagnostic method for detection of lymph node metastases]

In order to improve the sensitivity of diagnosis of regional lymph node metastases in cancer patients, the novel molecular method called the one-step nucleic acid amplification (OSNA) assay using cytokeratin 19 mRNA as a molecular marker was developed. In this method, the supernatant of a homogenized lymph node solution is directly analyzed without the mRNA purification process that is usually required in RT-PCR. Therefore the results are available within 30 min via a simple procedure, and the results correlate well with the number of cancer cells in the lymph node. We conducted multicenter clinical trials in Japan to evaluate the OSNA assay for the detection of lymph node metastases in breast cancer, colorectal cancer, gastric cancer, and lung cancer. The results showed that the OSNA assay provides a judgment performance equivalent to that of 2-mm-interval histopathologic examinations of lymph nodes in each type of cancer. Furthermore, the OSNA assay is unlikely to yield false-positives for histopathologically negative lymph nodes. Following these results, the OSNA assay was approved as a diagnostic method for lymph node status in breast, colorectal, and gastric cancer patients by the Japanese Ministry of Health, Labor and Welfare. The OSNA assay is promising as a quick, simple, subjective, quantitative method for the detection of lymph node metastases in various cancers.