Which mutations preclude cetuximab use in colorectal cancer?

All RAS mutations (KRAS and NRAS codons 12, 13, 59, 61, 117, 146) and BRAF V600E predict no benefit from cetuximab/panitumumab. Extended RAS testing (beyond KRAS exon 2) identifies an additional 15% of patients. Only RAS/BRAF wild-type patients should receive EGFR antibody therapy.

Does tumor sidedness affect cetuximab benefit in RAS WT colorectal cancer?

Yes, dramatically. Left-sided (splenic flexure to rectum) RAS WT mCRC: cetuximab + FOLFOX/FOLFIRI achieves ORR 65–70% and significant OS benefit. Right-sided RAS WT mCRC: cetuximab shows minimal benefit, VEGF inhibitors (bevacizumab) preferred. Sidedness is a clinical decision biomarker independent of RAS status.

Cetuximab KRAS Wild-Type Probability for Response

Assess KRAS/NRAS/BRAF mutation status impact on cetuximab and panitumumab response in metastatic colorectal cancer. RAS-mutated tumors do not benefit from EGFR antibodies.

Use the full interactive calculator below, or

Cetuximab KRAS Wild-Type Probability for Response

Frequently Asked Questions

Which mutations preclude cetuximab use in colorectal cancer?

Does tumor sidedness affect cetuximab benefit in RAS WT colorectal cancer?