Rapid diagnosis of lymph node metastasis in lung cancer with loop-mediated isothermal amplification assay using carcinoembryonic antigen-mRNA.

We investigated the clinical utility of our novel loop-mediated isothermal amplification (LAMP) assay developed as a rapid molecular diagnostic method, using carcinoembryonic antigen (CEA)-mRNA as a marker for detecting tumor cells in patients with non-small cell lung cancer (NSCLC). We evaluated the sensitivity of our LAMP technique using a known quantity of synthesized standard CEA-mRNA. On the basis of those results, we performed LAMP analysis of clinical specimens of 22 primary tumors and 144 lymph nodes obtained from 22 NSCLC patients, and compared the results with those of conventional reverse transcription-polymerase chain reaction (RT-PCR). Standard curves were obtained from the amplification products within 25 min using the LAMP method, which indicated that the limitation to detect extracted CEA-mRNA copies was 100 copies. Further, CEA-mRNA was detected in all 22 primary tumors. Of the 12 lymph nodes shown to be metastasis-positive by hematoxylin-eosin (H-E) staining, 10 showed significant amplification of products in the LAMP assay, while 2 micrometastatic nodes with less than 100 copies of CEA-mRNA were not detectable. Of the 132 histologically non-metastatic lymph nodes, 23 (17%) were judged to be metastasis-positive by the LAMP assay. As compared to the results obtained from conventional RT-PCR used as a control, the LAMP assay was 81% sensitive and 100% specific, while the negative and positive predictive values were 91% and 100%, respectively. These results suggest that our LAMP method using CEA-mRNA as a target molecule has potential to rapidly diagnose nodal metastasis in patients with NSCLC.