CtDNA-guided rechallenge with anti-EGFR therapy in RASwt metastatic colorectal cancer: Evidence from clinical practice.

Aim: To apply extended ctDNA-based RAS genotyping to clinical criteria for improving the selection of patients eligible for anti-EGFR-based rechallenge in a real-world setting.

Methods: ctDNA testing was prospectively applied to RASwt mCRC progressed after a first-line anti-EGFR-containing regimen and at least one other line. The primary endpoint was the objective response rate.

Results: Among ten enrolled patients, the anti-EGFR rechallenge resulted in an objective response rate and disease control rate of 70% and 90%. The median progression-free survival was 11.3 months and overall survival was not reached. Compared with a historical cohort retreated with anti-EGFR agents based on clinical criteria, the ctDNA-driven approach resulted in a higher chance of achieving an objective response and longer survival.

Conclusions: Blood-based RASwt status may enrich metastatic colorectal cancer more likely to benefit from anti-EGFR-based rechallenge. RAS genotyping in ctDNA represents a feasible, fast, and cost-effective tool to be implemented in the clinic for advancing precision medicine.