Surgical outcomes and recurrence risk factors for rectal gastrointestinal stromal tumors: A comparison of transabdominal and transanal resection.

Abstract

114 Background: Rectal gastrointestinal stromal tumors (GISTs) are rare mesenchymal neoplasms that present unique surgical challenges due to pelvic anatomy and the need for sphincter preservation. While transanal excision (TAE) is a minimally invasive option for small tumors, and transabdominal resection (TAR) is standard for larger lesions, the optimal approach for intermediate-sized (3-5 cm) tumors remains controversial due to a lack of comparative evidence. Therefore, this study analyzes the clinicopathological characteristics of rectal GISTs in a large single-center cohort, compares perioperative and survival outcomes between TAE and TAR for 3-5 cm tumors, and investigates risk factors for postoperative recurrence. Methods: This retrospective study included 97 patients who underwent surgical resection for rectal GIST at Zhongshan Hospital, Fudan University, between July 2006 and January 2023. Clinicopathological data and follow-up information (recurrence, metastasis, and overall survival [OS]) were collected. Patients were divided into two groups based on surgical approach: TAE and TAR. Perioperative outcomes, disease-free survival (DFS), and OS were compared between the two groups for tumors sized 3-5 cm. Risk factors for recurrence were analyzed using Cox regression models. Results: Of the 97 patients with rectal GIST, 37 had tumors sized 3-5 cm and were included in the comparative analysis (23 in the transanal excision [TAE] group and 14 in the transabdominal resection [TAR] group). Baseline clinicopathological characteristics were comparable between the two groups. For tumors sized 3-5 cm, the TAE group demonstrated significantly better perioperative outcomes than the TAR group, including shorter operative time (median [range], 180 [120-260] vs. 325 [210-420] minutes, P<0.001), less estimated blood loss (50 [0-270] vs. 225 [50-600] mL, P<0.001), and shorter postoperative hospital stay (6 [3-14] vs. 12 [7-24] days, P<0.001).After a median follow-up of 81.1 months, no significant difference was observed in disease-free survival (DFS) or overall survival (OS) between the TAE and TAR groups for 3-5 cm tumors (log-rank P=0.116 and P=0.089, respectively). Multivariable Cox regression analysis of the entire cohort (N=83) identified mitotic count >5/50 HPF (HR=8.88, P<0.001) and vascular invasion (HR=5.15, P=0.031) as independent risk factors for worse DFS, while postoperative imatinib therapy was an independent protective factor (HR=0.28, P=0.020). Conclusions: Our study shows that for carefully selected patients with 3-5 cm rectal GIST, TAE offers significant advantages in perioperative outcomes without compromising long-term oncologic prognosis. Recurrence is primarily driven by tumor biology (mitotic count, vascular invasion) and postoperative imatinib therapy confers a protective effect.