Detection of KRAS Mutations in Plasma DNA Using a fully Automated Rapid Detection System in Colorectal Cancer Patients

Abstract

KRAS mutations have been recognized as predictive markers of primary resistance to anti-EGFR-antibodies in colorectal cancer patients. In addition, newly detected KRAS mutations have been reported to be related with acquired resistance to chemotherapy containing anti-EGFR antibody. Considering this evidence, monitoring of KRAS mutations is indispensable for making treatment decisions, and the method should be non-invasive allowing repeated examinations. Recently, we established a novel automated sensitive detection system for KRAS mutations, named mutation-biased PCR quenching probe system (MBP-QP). The goal of our study was to investigate the potential for monitoring KRAS mutations during treatment with anti-EGFR antibodies. The detection limit of MBP-QP using a control plasmid containing KRAS mutations was 1-9 copies, and 0.05-0.3% mutant plasmid was detectable in a mixture of wild type and mutants. One-hundred twenty colorectal cancer patients were genotyped for KRAS mutations with MBP-QP as well as polymerase chain reaction reverse sequence-specific oligonucleotide (PCR-rSSO), which has already been applied to cancer tissue samples in the clinical setting. Concordance rates between plasma DNA and cancer tissues were 68% with MBP-QP and 66% with PCR-rSSO, indicating that these systems are equivalent in terms of detecting KRAS mutations with plasma DNA. KRAS mutations in plasma DNA were frequently observed in systemic metastatic cancer patients, and in three patients KRAS mutations appeared after chemotherapy containing anti-EGFR antibody. A prospective study is needed for clarifying whether KRAS mutations detected in plasma DNA are predictive markers of treatment efficacy with anti-EGFR antibody.

The Use of Circulating Tumor DNA to Monitor and Predict Response to Treatment in Colorectal Cancer

“…Mutations of genes related to the EGFR signalling pathway, such as in EGFR, KRAS, BRAF , and PIK3CA , have been measured in studies that have monitored the response to cetuximab and panitumumab in mCRC patients. The measurement of KRAS mutations in ctDNA show an increase in level of ctDNA prior to disease progression in a number of small (n < 10) descriptive studies (Yamada et al, 2016; Hosoya et al, 2017; Trojan et al, 2017; Ghatalia et al, 2018; Klein-Scory et al, 2018; Knebel et al, 2019). Another study of 24 KRAS WT patients undergoing treatment with chemotherapy and either cetuximab or panitumumab demonstrated that KRAS mutations could be detected in ctDNA in the majority of affected patients up to 3 months prior to detection of disease progression with a CT scan (Yamada et al, 2016).…”