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GIST — SCE Medical Oncology MCQ

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HardGI CancersGISTSCE Medical Oncology

A high-recurrence-risk small-bowel GIST is completely resected and sequencing shows PDGFRA D842V. Should adjuvant imatinib be prescribed?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: A — Do not use adjuvant imatinib because D842V causes primary resistance

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

B is correct. PDGFRA D842V stabilises an active kinase conformation to which imatinib binds poorly, producing primary resistance. A high Miettinen recurrence risk does not create drug sensitivity, so standard three-year adjuvant imatinib should not be used for this genotype. Dose escalation does not overcome D842V resistance, treatment duration cannot fix intrinsic resistance, and the mutation does not make recurrence impossible. Avapritinib has activity in advanced D842V-mutant GIST but has no established routine adjuvant role, which is why surveillance and specialist GIST review remain essential after resection.

Reference: PDGFRA D842V-mutant GIST molecular review: https://pubmed.ncbi.nlm.nih.gov/33572358/