Comparative efficacy of neoadjuvant imatinib therapy in gastric versus rectal gastrointestinal stromal tumors: a two-center retrospective cohort study

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OBJECTIVE: This study aimed to evaluate and compare tumor response, survival outcomes, and prognostic factors in gastric versus rectal GIST patients treated with neoadjuvant IM. METHODS: We conducted a two-center retrospective cohort study of 134 patients with locally advanced gastric (n = 83) and rectal (n = 51) GISTs who received neoadjuvant IM followed by surgery between 2012 and 2024. Radiologic and pathologic responses were assessed, and survival outcomes were analyzed using Kaplan-Meier and Cox regression models. RESULTS: Preoperative IM (Pre-IM) duration was stratified by the median of 9 months (IQR: 6–12 months). Before IM therapy, the mean tumor size was significantly larger in the gastric group than in the rectal group (12.07 ± 5.42 cm vs. 6.42 ± 2.96 cm, P < 0.001). Both groups demonstrated significant tumor shrinkage after IM (post-treatment size: 8.35 ± 4.33 cm vs. 4.25 ± 2.11 cm, P < 0.001), with comparable percentage reduction in size (29.7%±19.3% vs. 32.5%±17.7%, P = 0.402). Radiologic and pathologic response rates were also similar between the groups. However, rectal GISTs exhibited significantly better overall survival (5-year OS: 98.0% vs. 78.5%, P = 0.003) and a trend toward improved relapse-free survival (5-year RFS: 87.2% vs. 70.1%, P = 0.057). These survival benefits persisted across subgroups stratified by tumor size and Pre-IM duration, with a significant OS advantage observed in rectal GIST patients treated for ≥ 9 months (P = 0.025). Multivariate Cox regression confirmed rectal tumor location as an independent predictor of improved RFS (HR = 0.242, P = 0.022) and OS (HR = 0.044, P = 0.003). CONCLUSION: Gastric and rectal GISTs showed similar antitumor responses to neoadjuvant IM, while survival appeared more favorable for rectal tumors, particularly with extended Pre-IM. However, this result may be influenced by confounding factors and requires further validation in larger prospective studies.

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