Timing of Adjuvant Imatinib Initiation and Recurrence-Free Survival After Curative Resection for Intermediate- and...

Adjuvant imatinib reduces recurrence risk after curative resection for intermediate- and high-risk gastrointestinal stromal tumors, but the optimal timing of postoperative initiation remains unclear. This multicenter real-world cohort study evaluated 596 patients with modified National Institutes of Health intermediate- or high-risk gastrointestinal stromal tumors who underwent R0 resection followed by adjuvant imatinib therapy at five centers in China. Postoperative imatinib initiation timing was modeled as a continuous variable using a multivariable restricted cubic spline Cox model, and the derived threshold was further evaluated using propensity score overlap weighting. The lowest recurrence risk occurred at 6.22 weeks after surgery, with a 95% confidence interval of 1.29-7.65 weeks; therefore, 8 weeks was selected as a clinically interpretable threshold. After overlap weighting, baseline covariates were well balanced between the planned initiation group (≤ 8 weeks, n = 476) and delayed initiation group (> 8 weeks, n = 120). Delayed initiation was associated with worse 5-year recurrence-free survival (70.8% vs. 82.4%) and remained independently associated with an increased risk of recurrence-free survival events in weighted analysis. Severe postoperative complications were independently associated with delayed initiation. These findings suggest that unnecessary delays in adjuvant imatinib initiation should be minimized once postoperative recovery permits and support timely transition to adjuvant targeted therapy as part of postoperative gastrointestinal stromal tumor management.