Liquid biopsy has been adopted into one of diagnostic tests of EGFR mutation for patients with advanced or metastatic non-small cell lung cancer (NSCLC). Loop-mediated isothermal amplification (LAMP) has been widely used for the rapid detection in virology or bacteriology, which allows quick amplification of DNA (60 min) with certain cost-effectiveness (WHO recommendations on the use of TB-LAMP presents the price per test is 7 euros). Theoretically, LAMP could enable us to make a quick diagnosis of oncogene as well. Here we developed a set of unique primers for detecting EGFR mutations, and investigated the efficacy of EGFR-LAMP assay using plasma samples of patients with resected NSCLC tumor.
All samples were collected from patients with suspected primary lung cancer at Saitama Cardiovascular and Respiratory Center between January 2019 and September 2020. All tumor tissues were taken by surgery or surgical biopsy, and the EGFR status of them were investigated by the Therascreen EGFR PCR Kit. Among them, only cases with EGFR mutated tumors were selected for further investigation. The LAMP and NGS assays were conducted for DNA products extracted from preoperative plasma samples. The detection rates of both assays were calculated and compared each other.
Among 57 EGFR mutated tumors or metastatic lymph nodes, 51 preoperative plasma specimens were available for investigation of EGFR status by the NGS and the LAMP assays. The NGS assay detected only 2 EGFR-mutated samples (2/51), one of which showed EGFR mutation by the LAMP assay (1/51). The detection rates of EGFR mutation were extremely low in both assays (1.9% in the LAMP assay, and 3.9% in the NGS assay, respectively). The two cases were advanced papillary adenocarcinoma showing IIIA and IVA in pathological stage, while most of remaining cases consisted of stage I-II lung cancer (44/49).
This is the first report of LAMP liquid biopsy detecting oncogene in a plasma sample. The EGFR-LAMP assay similar performance to the NGS assay in terms of detecting EGFR mutation in NSCLC tumors. The LAMP assay has advantage of time-saving, cost-effective, and simple test compared to the NGS assay. However, further investigation is required for development of more sensitive assay.
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Legal entity responsible for the study
Eiken Chemical Co., Ltd.
A. Matsui, S. Michiyuki: Financial Interests, Personal and Institutional, Full or part-time Employment: Eiken Chemical Co., Ltd. All other authors have declared no conflicts of interest.