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Checkpoint Inhibitor Colitis — RACP Adult Medicine MCQ

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ModerateGastroenterologyCheckpoint Inhibitor ColitisRACP Adult Medicine

A 55-year-old man on pembrolizumab (anti-PD-1) for melanoma develops Grade 3 diarrhoea (>7 stools/day above baseline) with bloody stools at week 8 of treatment. CT shows colonic wall thickening. Colonoscopy shows diffuse mucosal inflammation. Stool C. difficile is negative. What is the most appropriate management?

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Correct answer: B — Hold pembrolizumab and start IV methylprednisolone 1-2 mg/kg/day

Grade 3 immune-mediated colitis (>7 stools/day, bloody, requiring hospitalisation) requires holding checkpoint inhibitor and commencing high-dose IV corticosteroids (methylprednisolone 1-2 mg/kg/day). If no improvement in 3-5 days, infliximab 5 mg/kg is second-line. C. difficile and CMV must be excluded. Grade 3-4 colitis may require permanent discontinuation. irAE colitis resembles IBD histologically.

Reference: ASCO – 2024 – irAE Management Guidelines; eviQ 2024