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Pseudoprogression Lung — SCE Medical Oncology MCQ

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HardLung CancerPseudoprogression LungSCE Medical Oncology

During pembrolizumab maintenance, a clinically well patient develops one new subpleural opacity with an organising-pneumonia pattern while all known tumour sites continue to shrink. Infection assessment is negative. What is the best interpretation and immediate strategy?

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Correct answer: B — Classify unconfirmed progression, assess immune pneumonitis and arrange short-interval confirmation imaging

Explanation lettering: E = shown as A · D = shown as B · A = shown as C · C = shown as D · B = shown as E

D is correct. A new lesion meets conventional progression criteria, but in a stable patient receiving immunotherapy iRECIST classifies the first event as unconfirmed until repeat imaging establishes growth or additional disease. The organising-pneumonia morphology and discordant response also require assessment for immune pneumonitis; biopsy is useful when diagnosis would materially alter care. Pseudoprogression cannot be presumed, infection still requires clinical exclusion, and neither antifungal therapy nor SABR follows automatically from one pattern. Symptoms, oxygenation or more extensive pneumonitis would require urgent toxicity treatment rather than simply waiting for confirmation.

Reference: iRECIST guideline: https://pmc.ncbi.nlm.nih.gov/articles/PMC5648544/