A 65-year-old patient with MSI-H (mismatch repair deficient) colorectal cancer metastatic to the liver presents for first-line treatment. She has KRAS/NRAS/BRAF wild-type tumor. What is the most appropriate first-line systemic therapy?

• A FOLFOX + cetuximab
• B FOLFOXIRI + bevacizumab
• C Pembrolizumab monotherapy ✓
• D FOLFIRI + panitumumab

Explanation

The KEYNOTE-177 trial demonstrated that pembrolizumab (anti-PD-1) monotherapy provides superior progression-free survival compared to chemotherapy as first-line treatment in MSI-H/dMMR metastatic colorectal cancer, with fewer adverse effects. This established immunotherapy as the preferred first-line option for this molecular subtype. EGFR inhibitors (cetuximab, panitumumab) benefit RAS/BRAF wild-type left-sided tumors but do not specifically target MSI-H status. FOLFOXIRI + bevacizumab is used for high-burden disease but is not preferred over pembrolizumab in dMMR tumors.

Reference: Bailey & Love's Short Practice of Surgery, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.