Skip to main content
2026 ASCRS Annual Scientific Meeting Main banner
Icon Legend
This session is not in your schedule.
This session is in your schedule. Click again to remove it.
Presentation Icons
CME
CME
Invitation/Ticketed Event
Invitation/Ticketed Event
Invited Lectureship
Invited Lectureship
Award Recipient
Award Recipient
Live Streamed Session
Live Streamed Session
Nurses Contact Hours
Nurses Contact Hours
Self-Assessment
Self-Assessment
Live Q&A and Polling
Live Q&A and Polling
Social
Social
Industry
Industry

Session:: ePosters-Sun1230-M4: Other Neoplasia and Endoscopy

EP396 - Treatment Modalities And Outcomes In Anal Gastrointestinal Stromal Tumors: A National Cancer Database Analysis

Sunday, May 10, 2026
1:08 PM - 1:13 PM ET

    ePoster Presenter(s)

  • Alexia Benson, MD

    Research Fellow
    University of South Florida
    University of South Florida
    Tampa, FL, United States

    Disclosure information not submitted.

    View ePoster

    • Senior Author(s)

  • PC

    Paul Cavallaro, MD

    Assistant Professor of Surgery
    University of South Florida
    Tampa, Florida, United States

    Disclosure information not submitted.

    • Author(s)

  • Taylor L. Garza, MD

    Resident
    University of South Florida
    University of South Florida
    Tampa, FL, United States

    Disclosure information not submitted.

  • JM

    Jorge Marcet, MD

    Director, Division of Colon and Rectal Surgery
    USF Morsani College of Medicine
    Tampa, Florida, United States

    Disclosure information not submitted.

  • Robert D. Bennett, MD

    Attending Physician
    University of South Florida
    Tampa, Florida, United States

    All disclosed relationships have been reviewed and managed prior to the start of this activity. Any relevant relationships will be listed below. This individual has no financial relationships to disclose

  • AC

    Allen P. Chudzinski, M.D.

    Professor of Surgery
    University of South Florida Morsani College of Medicine
    Tampa, Florida, United States

    Disclosure information not submitted.

  • CM

    Carolina Martinez, MD

    Assistant Professor
    University of South Florida
    Tampa, Florida, United States

    Disclosure information not submitted.

Purpose/Background: Gastrointestinal stromal tumors (GISTs) comprise less than 1% of digestive tract malignancies, with anal primaries representing an exceptionally rare subset. Prior registry-based studies are limited to a National Cancer Database (NCDB) study (1998-2012) on resected anorectal tumors (N=333) and a SEER analysis that considered the anal and rectal sites as a singular primary. We conducted an updated NCDB analysis spanning data from 2004 to 2022 to include demographics, tumor characteristics, treatment modalities and outcomes, evaluating rectal and anal GISTs as separate primaries as the latter remain poorly defined in existing literature.

Methods/Interventions: Patients with anal and rectal GISTS diagnosed between 2004 and 2018 were identified from the NCDB using the ICD-O-3 histology code 8936. Primary site codes for anus (also taking into consideration overlapping sites of the anus and rectum) included C21.0, C21.1, C21.8.

Variables of interest included demographics, tumor characteristics and treatment modalities such as primary site surgery, use of neoadjuvant therapy, systemic therapy following surgery and surgical margin status. Descriptive analyses were performed to assess treatment patterns and outcomes.

Results/Outcomes: In this cohort, a total of 1266 patients were included, of which only 55 were anal GISTs. Median age was 65 years (range 40-90) and there was a statistically significant difference in sex distribution (p < 0.01) with 22 (40%) males, 33 (60%) females with anal primary. The median tumor size was 41.5mm.

Among the 55 patients, four (7%) did not receive any treatment. Sixteen (29%) underwent surgery alone (14 local excisions and 2 APRs), of which three (18.7%) showed positive tumor margins (all local excisions). Thirteen (23.6%) received chemotherapy alone. Eight (14.5%) received neoadjuvant chemotherapy with surgery (5 local excisions and 3 APRs), of which five (62.5%) showed positive tumor margins (4 local excisions and 1 APR). Thirteen (24%) underwent surgery followed by adjuvant systemic therapy, of which eight (61.5%) had evidence of residual tumor margins.

When examining tumor size with sequence of systemic therapy and surgery, patients who did not receive either systemic therapy or surgery had a mean tumor size of 37.36 mm, those who received neoadjuvant therapy prior to surgery had a larger median tumor size of 62.4 mm and those patients who received systemic therapy after surgery had a mean tumor size of 36.35 mm.

Based on primary site and surgical margins, higher percentages of residual tumor burden were evident in anal GIST tumors (50%, 42.8%, 37.5%) compared to rectal (23.7%), and among the anal tumors, the anal canal tumors had the highest percentages of residual tumor margins (50%).

Conclusion/Discussion: Management of anal GISTs is not clearly defined in existing literature. In this national cohort, residual tumor burden was frequent, particularly after local tumor excision and despite neoadjuvant therapy, likely due to patient and surgeon preference to maintain sphincter function and avoid a stoma. Further studies on optimal treatment strategies are needed for these rare tumors.

Mean tumor size vs Surgical Procedure
Mean tumor sizes were compared against the surgical procedures - None, Local tumor excision, or abdominoperineal resection, based on 3 subcategories of anal primary (site codes C21.0, C21.1, C21.8)