PDGFRA and gastrointestinal stromal tumor: Treatment with imatinib, a tyrosine kinase inhibitor, in GIST harboring a variant in exon 11 of KIT, has significantly improved the survival for patients with advanced disease from 18 to more than 70 months.7,8 Response to imatinib is dependent on the specific underlying genotype, such as mutations in KIT exon 11 rendering a better response rate compared with KIT exon 9 variants.5 Avapritinib, a new targeted therapy, has proven excellent efficacy in PDGFRα p.Asp842Val GIST, known to be resistant to imatinib.8,9