• Histologically confirmed colorectal adenocarcinoma

• Initial RAS/BRAF wild-type status

• Received first-line treatment with FOLFOX, FOLFIRI, or FOLFOXIRI combined with cetuximab, with documented clinical benefit (CR/PR/SD) and progression-free survival (PFS) ≥ 6 months

• Disease progression occurred during or within 3 months after cetuximab-based first-line therapy

• Experienced further tumor progression after receiving second-line or subsequent treatments

• At least 4 months have elapsed since the last administration of cetuximab

• At least one measurable lesion according to RECIST v1.1

• RAS/BRAF wild-type status confirmed by blood-based ctDNA testing

• Normal hematologic function (platelets \> 90 × 10⁹/L; white blood cells \> 3 × 10⁹/L; neutrophils \> 1.5 × 10⁹/L; hemoglobin \> 10.0 g/100 ml)

• Serum bilirubin ≤ 1.5 × upper limit of normal (ULN), transaminases ≤ 5 × ULN

• No ascites, normal coagulation function, serum albumin ≥ 35 g/L

• Child-Pugh class A liver function

• Serum creatinine below ULN or calculated creatinine clearance \> 50 ml/min (using the Cockcroft-Gault formula)

• ECOG performance status of 0-1

• Expected survival \> 3 months

• Signed written informed consent

• Willing and able to undergo follow-up until death, study completion, or study termination