RAS Mutational Status Detection in Tissue, Plasma, and Stool Samples for Colorectal Cancer

OBJECTIVE: RAS gene testing on tumor tissue biopsies is required for metastatic colorectal cancer (CRC) patients. However, it is infeasible for patients after curative surgery and repeated biopsy. This study is aimed at evaluating the consistency of RAS genes in patient's plasma, stool, and tumor tissue samples, to explore whether plasma and stool samples can supplement or replace tumor tissue to assess baseline RAS gene status. METHODS: Between June 2016 and October 2017, 53 patients with stage I-IV CRC from the Liaoning Cancer Hospital and the Department of Medical Oncology of the First Hospital of China Medical University were enrolled in the study. Patient tissues, peripheral blood, and stool samples were collected, and RAS gene tests were performed. RESULTS: Analysis of the KRAS gene in tissue, plasma, and stool samples from 53 CRC patients detected 25 cases (47%) of KRAS gene mutations in the tissue samples, 20 cases (38%) of KRAS gene mutations in plasma, and 18 (34%) KRAS gene mutations in fecal samples. The overall consistency of KRAS gene status between tissue samples and plasma samples was 77.4% (p ≤ 0.05) and between tissue samples and stool samples was 83% (p ≤ 0.05). In stage IV cases, the agreement of KRAS gene status between tissue and plasma samples was 93.8% (p ≤ 0.05) and 93.8% (p ≤ 0.05) between tissue and stool samples. CONCLUSION: There was a high overall consistency in KRAS mutational assessment between plasma, stool, and tissue samples. In stage IV patients, the consistency of KRAS gene detection between tissue and stools or plasma was higher.