Liquid biopsy for optimizing the rechallenge of cetuximab in metastatic colorectal cancer: Additional study of E-Rechallenge Trial.

585Background: Several previous reports indicated that cetuximab (Cmab) rechallenge may be efficacious in some patients for whom Cmab was previously effective. Liquid biopsy can detect the some emerging mutations for resistance with Cmab. Considering the plasticity and elasticity of sensitive clone, we assumed we could identify the patients with benefit from Cmab rechallenge by liquid biopsy. This current study investigates the predictability of efficacy for Cmab rechallenge by liquid biopsy in the E-Rechallenge Trial. Methods: The E-Rechallenge Trial is a multicenter phase II study in mCRC patients who have become refractory to fluoropyrimidines, L-OHP, CPT-11, Cmab, and bevacizumab, and in whom previous treatment with Cmab was effective in any earlier line (achieving CR, PR, or SD that persisted for ≥ 6 months). The other main eligibility criteria are; RAS wild type, measurable disease, aEFI ≥ 16 weeks between the last dose of Cmab during previous treatment and the start of Cmab rechallenge. Protocol tr...