[Re-Administration of Anti-EGFR Antibody Drugs for Unresectable Colorectal Cancer-Focusing on Tumor Markers].

The 2022 edition of the Guidelines for the Treatment of Colorectal Cancer described rechallenge therapy as a backward treatment for unresectable colorectal cancer, but currently, there is no evidence to support its benefit. We reviewed 6 cases of rechallenge therapy in which tumor marker trends could be followed in our department. Two cases had a rapid decline in tumor markers that was maintained for 7-8 months. In 3 cases, PR was also confirmed on imaging. In contrast, there was 1 case with no decrease in tumor markers at all. Our findings suggest that cases of wild-type RAS prior to rechallenge therapy and cases that are responsive to initial anti-EGFR antibody drugs may have been involved in the effect of rechallenge therapy.