A 60-year-old man undergoes a right hemicolectomy for stage III colon cancer. Pathology shows a KRAS mutation in exon 2. Which targeted therapy is contraindicated for this patient if metastatic disease develops?

• A Bevacizumab (anti-VEGF)
• B Pembrolizumab (anti-PD-1)
• C Regorafenib (multi-kinase inhibitor)
• D Cetuximab (anti-EGFR) ✓

Explanation

Anti-EGFR monoclonal antibodies like cetuximab and panitumumab are only effective in patients with wild-type RAS (KRAS and NRAS exons 2, 3, and 4). A KRAS mutation constitutively activates the downstream signaling pathway, rendering EGFR blockade ineffective. Bevacizumab targets VEGF and is independent of KRAS status. Pembrolizumab is indicated specifically for MSI-H/dMMR tumors.

Reference: Cancer Principles and Practice of Oncology (DeVita, Hellman, and Rosenberg's), 12th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.