The FDA has granted approval to cetuximab (Erbitux) for use in combination with FOLFIRI (irinotecan, fluorouracil, leucovorin) for first-line treatment of patients with KRAS mutation–negative (wild-type), EGFR-expressing metastatic colorectal cancer as determined by FDA-approved tests for this use. FDA also approved the TheraScreen KRAS RGQ PCR Kit (by QIAGEN) concurrently with this cetuximab approval.
The approval was based on retrospective analyses in the patient subsets according to KRAS mutation status in tumor samples from patients enrolled in the CRYSTAL trial and in two supportive studies, CA225025 and EMR 62 202-047 (or OPUS trial). The addition of cetuximab to chemotherapy or best supportive care resulted in improved overall survival, progression-free survival, and overall responses rates in the subset with KRAS wild-type tumors, whereas there was no benefit or potential harm in patients with KRAS mutant tumors.
The approval of the companion diagnostic, the TheraScreen KRAS RGQ PCR Kit, provides a reliable way to identify these subsets of patients with colon cancer. This genetic assay is a real-time polymerase chain reaction assay detecting seven different mutations of the KRAS gene in a tumor specimen.
The recommended dose and schedule for cetuximab is 400 mg/m2 administered intravenously as a 120-minute infusion as an initial dose, followed by 250 mg/m2 infused over 30 minutes weekly in combination with FOLFIRI. Cetuximab administration should be completed 1 hour prior to FOLFIRI.
Product labeling for cetuximab provides “limitation of use” information specifying that the drug is not indicated for treatment of KRAS mutation–positive colorectal cancer. ■