MSI-H CRC Immunotherapy — RACP Adult Medicine MCQ

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ModerateMedical OncologyMSI-H CRC ImmunotherapyRACP Adult Medicine

A 55-year-old man with newly diagnosed colorectal cancer. Tumour is MSI-H/dMMR. First-line systemic therapy for metastatic disease?

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Correct answer: D — Pembrolizumab monotherapy

MSI-H/dMMR mCRC: first-line pembrolizumab (KEYNOTE-177). Higher CR rate than chemo. May also indicate Lynch syndrome – germline testing needed.

Reference: Cancer Council – 2022; PBS – 2025