EP1049 - Organ-Preserving Wide Local Excision for Rectal Gastrointestinal Stromal Tumors: A Case Series from a Tertiary Center

Purpose/Background: Rectal gastrointestinal stromal tumors (GISTs) are rare, accounting for < 5% of all GISTs. Their deep pelvic location poses unique challenges for sphincter preservation and oncologic clearance. The advent of neoadjuvant tyrosine kinase inhibitors (TKIs) such as imatinib has enhanced the feasibility of organ preservation and safer resections. Multidisciplinary strategies and minimally invasive techniques are central to optimizing outcomes.

Methods/Interventions: We conducted a retrospective review of four patients with histologically confirmed rectal GIST treated at a tertiary referral center between 2020 and 2023. Clinical presentation, tumor characteristics, treatment modalities, operative details, pathology, and follow-up outcomes were analyzed. All patients were discussed at a multidisciplinary tumor board.

Results/Outcomes: All four patients underwent wide local excision without formal rectal resection, achieving negative margins and no postoperative recurrence. The first patient, a 41-year-old male with a 9.9 cm low rectal GIST, received neoadjuvant imatinib and underwent combined laparoscopic-transanal wide local excision with diverting colostomy in December 2023. He remains disease-free at 20 months. The second patient, a 40-year-old female with a 7.5 cm anterior anorectal mass and high mitotic index, underwent transperineal wide local excision with partial vaginal resection and VRAM flap reconstruction in May 2023. She remains recurrence-free at 27 months. The third patient, a 36-year-old female with recurrent rectal GIST and peritoneal/ovarian dissemination, underwent laparoscopic omentectomy, left oophorectomy, and transperineal wide local excision of rectal disease in March 2023 . She remains disease-free at 26 months. The fourth patient, a 58-year-old male with a 6 cm bilobed pelvic mass abutting the rectum and puborectalis, underwent transperineal wide local excision in March 2020. He remains recurrence-free at 48 months.

Patients 1-3 received neoadjuvant imatinib and subsequently completed 3 years of adjuvant therapy. No perioperative complications occurred.

Conclusion/Discussion: Rectal GISTs, though rare, can be effectively managed with organ-preserving wide local excision using minimally invasive and transperineal approaches. Neoadjuvant imatinib facilitated tumor downsizing and safe resection in three patients. Plastic surgical reconstruction was beneficial in one complex case. All patients achieved R0 resection and remained recurrence-free, supporting wide local excision as a viable, organ-preserving strategy in selected patients.

Summary of Rectal GIST Cases