The results from randomized clinical trials indicate that adjuvant imatinib improves recurrence-free survival when administered after surgery to patients with operable gastrointestinal stromal tumor (GIST), and in one trial1 3 years of treatment with adjuvant imatinib improved also overall survival compared with 1 year of imatinib. At present, 3 years of adjuvant therapy with imatinib is considered the standard of care for patients who have undergone surgery for high-risk GIST, unless the tumor harbors a mutation that confers resistance to imatinib (eg, PDGFRA exon 18 mutation D842V) or is wild-type for both KIT and PDGFRA.