PDGFRA and gastrointestinal stromal tumor: Primary resistance refers to the progression of tumors during the first six months of treatment, mainly seen in KIT exon 9 mutant GIST and PDGFRA exon 18 D842 V mutant GIST treated with 400 mg of imatinib per day, as well as wild-type (mainly SDH-deficient) GIST, accounting for 10%-14%.