Optimal Anti-EGFR Treatment of mCRC Patients With Low-Frequency RAS Mutation

The present hypothesis is that anti-EGFR agents are active in tumors with low-level RAS mutation when the majority of tumor cells is still sensitive. While response rate may be high and may reflect sensitivity to anti-EGFR agents, PFS is anticipated to be shorter than in RAS wild-type patients due to the faster development of resistance when sensitive cells are eradicated and when the RAS-mutant anti-EGFR resistant clones become predominant. The characteristics of low-level RAS mutant tumors would be: * Objective response rate (ORR) high (reflecting the sensitive clone) * Progression-free survival (PFS) short (reflecting the more rapid outgrowth of RAS mutant clones)