Moreover, in the majority of patients with PDGFRα D842V-mutant GIST treated with avapritinib, ctDNA levels fell below the limit of detection (0.05%) by two months on treatment and large declines in on-treatment ctDNA levels were associated with high baseline ctDNA, an independent risk factor for progression. The gene discussed is PDGFRA; the disease is gastrointestinal stromal tumor.