Adjuvant Imatinib for Patients Resected for <scp>GIST</scp> : A Quality Assurance Study

BACKGROUND: The administration of adjuvant Imatinib for three years is a standard care of treatment in Denmark and indicated after resection of GIST with high and intermediate risk of recurrence. There are no reported real-world data on the safety of the treatment and the impact of adjusted treatment for the outcome of recurrence. METHODS: This is a retrospective study quality assuring the tolerability of three-year treatment and amplify this duration effective to reduce the risk of relapse. The primary endpoint is to assure the safety of the treatment. Secondary endpoints are recurrence-free-survival and overall survival. RESULTS: From January 1st 2019 to 31st December 2023, 225 patients were collected, 71 were referred to adjuvant treatment. Further six patients were excluded due to a short follow-up, ending with 65 eligible patients for inclusion. In a median follow-up of three years, a total of 60% were reduced in dosage due to toxicity, majority continuing with 400 mg and 17% were interrupted due to toxicity. There was no significant difference in the group of recurrence and treatment reduction or interruption. A total of 23% had relapse with a median time from diagnosis to recurrence of 4.5 years. INTERPRETATION: Three years of adjuvant Imatinib is a tolerable duration with no significant rate of recurrence among patients who were reduced or interrupted in treatment due to toxicity. This study reports a significance between high mitotic index and the relapse rate and a relation between recurrence and tumor site, tumor size and KIT exon 9 mutation.