Plasma Dynamics of RAS/RAF Mutations in Patients With Metastatic Colorectal Cancer Receiving Chemotherapy and Anti-EGFR Treatment.

BACKGROUND: RAS and RAF mutations in colorectal cancer (CRC) hold value in precision medicine. Liquid biopsy is an alternative to tumor tissue biopsy, and circulating tumor DNA (ctDNA) has been intensively investigated, but the clinical relevance of RAS and RAF mutations in plasma is yet to be determined. This study aimed to investigate the clinical aspects of RAS/RAF mutations during combination treatment.

PATIENTS AND METHODS: Patients with RAS/RAF tumor wild-type metastatic CRC treated with combination chemotherapy and an EGFR inhibitor were included. Blood samples were collected at baseline and every treatment cycle and analyzed for 31 RAS, RAF, and EGFR mutations until progressive disease or censoring using droplet digital PCR.

RESULTS: Forty-six patients were prospectively enrolled onto the study. At baseline, 7% had detectable RAS/RAF mutations in ctDNA. During the treatment course, the fraction of patients with mutated ctDNA increased to 22%. The emergence of mutations did not correlate with response or risk of progression while receiving treatment (P = 1.0).

CONCLUSION: Emergence of plasma RAS/RAF mutations was not correlated with the effect of combination chemotherapy and EGFR inhibition in patients with RAS/RAF wild-type metastatic CRC.