Monitoring of RAS mutant clones in plasma of patients with RAS mutant metastatic colorectal cancer

ABSTRACT

PurposeSome patients with histologically confirmed primary mCRC and mutated RAS reported undetectable RAS mutant clones in plasma after receiving anti-VEGF treatment. The aim was to prospectively assess it with its potential therapeutic implications.MethodsRAS mutant genes in solid biopsy (before first-line treatment FOLFOX/CAPOX + bevacizumab) were compared in liquid biopsy (before second-line treatment panitumumab + FOLFIRI), using Idylla™ system. Discordant results between solid/liquid biopsies were assessed by the next-generation sequencing (NGS) test (solid/liquid biopsies).ResultsTwenty-three patients were assessed (seven had RAS mutant discrepancies between solid/liquid biopsies). The NGS test confirmed that 3/23 (13%) patients had undetectable RAS mutant clones in liquid biopsy and 3/23 (13%) presented discrepancies in solid biopsy (Idylla™ system vs. NGS test).ConclusionThirteen percentage of patients had undetectable RAS mutant clones in liquid biopsy after first-line treatment. However, some discrepancies between solid and liquid biopsies have been observed. These results suggest a need to improve accuracy of RAS analyses, especially in solid biopsies.