The reason for this phenomenon may be complicated, but the prognosis of patients with KIT exon 9-mutated GISTs is worse than that of patients with other GISTs [25,26], and KIT exon 9-mutated GIST patients are also the only mutation genotype deriving a significant benefit in progression-free survival from the higher imatinib dose (800 mg/day) [26], which may explain the difference between the MDT and non-MDT groups. The gene discussed is KIT; the disease is gastrointestinal stromal tumor.