Perioperative Imatinib Treatment Continuation Patterns and Long-Term Outcomes in Locally Advanced Gastrointestinal Stromal Tumors After Neoadjuvant Therapy: An Exploratory Two-Center Retrospective Study.

PURPOSE: To describe perioperative imatinib continuation patterns and explore associations with long-term outcomes in patients with locally advanced gastrointestinal stromal tumors (GIST) undergoing curative-intent surgery after neoadjuvant therapy. MATERIALS AND METHODS: We retrospectively screened 395 patients receiving preoperative imatinib at two centers from 2012 to 2024. The analytic cohort comprised 171 patients with primary locally advanced GIST who underwent curative-intent surgery after neoadjuvant imatinib. Total perioperative exposure combined neoadjuvant and adjuvant treatment durations. Kaplan-Meier, Cox regression, and a 36-month landmark analysis were performed. Recurrence patterns and post-recurrence management were reviewed in 39 recurrent cases. RESULTS: Median follow-up was 46 months; 39 patients (22.8%) recurred and 20 (11.7%) died. Five-year overall survival was 76.1%, 91.7%, and 96.7% for total exposure ≤36, >36 to ≤48, and >48 months, respectively, whereas recurrence-free survival did not differ significantly. In the landmark cohort (n=97), exposure >36 months was not significantly associated with post-landmark recurrence-free survival (HR, 0.881; 95% CI, 0.319 to 2.431; P=0.807) or overall survival (HR, 0.238; 95% CI, 0.043 to 1.303; P=0.098). Liver metastasis (53.8%) and peritoneal/abdominal dissemination (48.7%) were the most frequently documented first recurrence sites; 38.5% had multisite recurrence and 15.4% received local treatment. CONCLUSION: Longer perioperative imatinib exposure showed favorable survival patterns in fixed-exposure analyses, but the association was attenuated in landmark analysis. These surgery-conditioned findings are exploratory and do not establish an optimal treatment duration.