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Metastatic CRC — RACP Adult Medicine MCQ

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ModerateMedical OncologyMetastatic CRCRACP Adult Medicine

A 70-year-old woman with metastatic colorectal cancer achieves a partial response to FOLFOX chemotherapy. Molecular testing shows the tumour is KRAS/NRAS wild-type and microsatellite stable. What targeted agent can be added to chemotherapy?

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Correct answer: C — Cetuximab (anti-EGFR)

For metastatic CRC that is RAS wild-type (KRAS and NRAS), anti-EGFR therapy (cetuximab or panitumumab) can be added to chemotherapy. RAS mutations predict resistance to anti-EGFR therapy. Bevacizumab is an alternative regardless of RAS status. Pembrolizumab is first-line for MSI-high/dMMR tumours only (KEYNOTE-177 trial), not MSS tumours. PBS criteria in Australia require confirmed RAS wild-type for anti-EGFR agent funding.

Reference: Cancer Council Australia – 2022 – CRC Optimal Care Pathway; PBS – 2025 – Cetuximab Listing