A Trial Protocol of Precision Medicine for Patients with RAS Wild Metastatic Colorectal Cancer Using Liquid Biopsy (RAS-liquid Study): A Prospective, Multicenter Observational Study

Abstract

Background: Anti-epidermal growth factor receptor (EGFR) therapy has been identified to prolong the survival of metastatic colorectal cancer (mCRC) patients without RAS mutations. However, its efficacy is not always consistent for these patients. Genomic profiles of primary tumors and metastases are not always concordant; thus, chemotherapeutic agents can alter the tumor molecular profile. This molecular heterogeneity may explain resistance to anti-EGFR therapy. Liquid biopsy using circulating tumor DNA (ctDNA) is a novel, non-invasive diagnostic tool that can accommodate this molecular heterogeneity, providing a comprehensive, real-time view of the molecular landscape. In this study, we evaluated the predictive value of genomic mutations in ctDNA for primary and acquired resistance to anti-EGFR therapy. Methods/Design: This study is a prospective, multicenter, observational study of mCRC patients with wildtype tissue RAS treated with cytotoxic agents and anti-EGFR antibodies as first-line therapy. Genomic mutations, including RAS, BRAF, PIK3CA, and EGFR in ctDNA, are assessed via Droplet Digital PCR before starting chemotherapy and every 3 months thereafter until disease progression. The target sample size is estimated to be 100. The primary endpoint is the response rate in patients without RAS mutation in their blood sample before starting chemotherapy. Discussion: This study will clarify the predictive value of baseline RAS mutation in ctDNA for responses to anti-EGFR therapy; the frequency of emerging RAS, BRAF, PIK3CA, and EGFR mutations in ctDNA; and the association with secondary resistance to anti-EGFR therapy in first-line therapy for wild-type tissue RAS mCRC patients.

Multicenter, single‐arm, phase II study of the continuous use of panitumumab in combination with FOLFIRI after FOLFOX for RAS wild‐type metastatic colorectal cancer: Exploratory sequential examination of acquired mutations in circulating cell‐free DNA

“…Droplet digital PCR can offer the possibility to detect mutant DNA at allele frequencies below 0.5% 16 . Furthermore, in a recent study, the protocol involved the application of a mutation allele frequency threshold above 0.1% 17 . Considering these factors, we adapted two cut‐off values to determine RAS/BRAF mutations.…”

“…16 Furthermore, in a recent study, the protocol involved the application of a mutation allele frequency threshold above 0.1%. 17 Considering these factors, we adapted two cut-off values to determine RAS/BRAF mutations. One was the conventional cut-off value for detecting RAS/BRAF mutations in formalin-fixed paraffinembedded samples (300 indexes for the majority of mutation detection beads).…”

Liquid biopsy to detect resistance mutations against anti-epidermal growth factor receptor therapy in metastatic colorectal cancer

“…Clinical studies are currently being conducted to standardize the frequency of sampling and interpretation of results. Two prospective studies have attempted to establish the prognostic value of liquid biopsy protocols; both studies including periodic three-monthly ctDNA analyses and clinical follow-up in CRC wt KRAS patients exposed to 5-fluorouracil regimens plus anti-EGFR antibodies[ 72 , 73 ]. Finally, current international guidelines, such as ESMO, have concluded that although there is insufficient evidence to recommend follow-up with liquid biopsy, such analysis could be useful for detecting secondary resistance to anti-EFGR[ 4 ].…”