A randomized study of 6 vs 3 years of adjuvant imatinib in patients with localized GIST at high risk of relapse.

Abstract

Background: The administration of adjuvant imatinib during three years is indicated after resection of primary localized GIST at high risk of recurrence, but many patients relapse afterwards.

Methods: IMADGIST (NCT02260505) was a multicenter open-label, randomized phase III study evaluating the maintenance of imatinib for 3 more years (6-years arm) compared to Interruption (3-years arm) from the day of randomization, conducted in the French Sarcoma Group. The primary endpoint was intent-to treat disease-free survival (DFS). Secondary endpoints include overall survival, time to imatinib resistance, response after imatinib reintroduction at relapse, safety.

Results: From December 24^th 2014 to April 4^th 2023; 136 patients aged ≥18, ECOG PS ≤2, with a localized GIST with a R0 or R1 surgery, and a risk of tumor recurrence ≥35% according to NCCN risk classification were randomized in 14 centers. Sixty-five patients were randomized to the 3-Years arm vs. 71 in the 6-Years arm. There were 68 males and females. Primary sites were gastric and small bowel in 60 (44%) and 64 (47%) patients respectively. Respectively 52 (38%) and 71 (52%) of patients had a risk of relapse of 35-70% and >70%.. With a median follow-up of 55 (IQR=46-59) months post randomization, DFS was significantly superior in the 6-Years arm (HR: 0.40 [0.20-0.69], p=0.0008). Time to imatinib resistance, survival, adverse events and quality of life are not different in the 2 arms.

Conclusions: Three additional years of adjuvant imatinib reduces the risk of relapse in patients who have received 3 years of adjuvant imatinib with an acceptable tolerance.