(P 201) METASTATIC PATTERNS, TREATMENT MODALITIES, AND OVERALL SURVIVAL IN OLIGOMETASTATIC GIST: A SINGLE-CENTER RETROSPECTIVE STUDY

Author(s)

Hayes Pearce, BS

Medical Student
University of Miami Miller School of Medicine
MIAMI, Florida, United States

Co-Author(s)

LS

Leonardo Simonelli, MS

University of Miami Miller School of Medicine
Princeton Junction, New Jersey, United States
NS

Nikita Sharma, BS

University of Miami Miller School of Medicine
Miami, Florida, United States
MM

Maiya-Mari Messina, BS

University of Miami Miller School of Medicine
Miami, Florida, United States
YC

Yu-Cherng Channing Chang, MD

University of Miami Hospital, Department of Radiology
Miami, Florida, United States
MS

Mohammed Saleh, MD

University of Miami Hospital, Department of Radiology
Miami, Florida, United States
Gina D'Amato, MD

Professor of Medicine/Sarcoma Medical Oncology
University of Miami Sylvester Comprehensive Cancer Center
Miami, Florida, United States
Emily Jonczak, MD (she/her/hers)

Assistant Professor; Division of Oncology; Sarcoma
Sylvester Comprehensive Cancer Center
Miami, Florida, United States
Jonathan C. Trent, MD, PhD

Director
Sarcoma Medical Research Program, University of Miami – Sylvester Comprehensive Cancer Center
Miami, Florida, United States
AL

Alan Livingstone, MD

University of Miami Hospital, Department of Surgical Oncology
Miami, Florida, United States
DF

Dido Franceschi, MD

University of Miami Hospital, Department of Surgical Oncology
Miami, Florida, United States
NM

Nipun Merchant, MD

University of Miami Hospital, Department of Surgical Oncology
Miami, Florida, United States
CH

Caitlin Hester, MD

University of Miami Hospital, Department of Surgical Oncology
Miami, Florida, United States
Francesco Alessandrino, MD (he/him/his)

Assistant Professor In Clinical Radiology
University of Miami Miller School of Medicine
Miami, Florida, United States
JG

Julie Grossman, MD

Assistant Professor of Surgery
University of Miami Hospital, Department of Surgical Oncology
Miami, Florida, United States

Objective: Treatment of oligometastatic gastrointestinal stromal tumor (GIST), defined as fewer than five metastatic lesions, remains challenging. Metastatic site and patient factors guide management, limiting consensus on treatment and prognosis. We evaluated whether overall survival (OS) varies by metastatic site, ethnicity, and treatment.

Methods: We queried our prospectively maintained pan-sarcoma database for subjects with biopsy-proven GIST cases (Jan 2011–June 2025), collecting data on genomics, metastases, treatment, ethnicity, and OS. Associations between treatment and metastatic sites were assessed by Chi-square tests. OS for metastatic sites and treatments were estimated by Kaplan-Meier analysis and compared by log-rank test. The Mantel-Haenszel test was used to calculate hazard ratios (HR).

Results: Of 525 subjects, 96 (18.3%) had oligometastatic GIST (median age at diagnosis: 54 years; median OS: 13.9 years; 49/47 M/F). 91.6% were KIT-positive (exon 11: 66; exon 9: 15; exon 17: 7). No association was found between exon status and OS. The liver was the most frequent metastatic site (43), then peritoneum (38) and lymph nodes (4). There was no significant OS difference for liver vs peritoneal metastases or Hispanic vs non-Hispanic ethnicity. Notably, surgery plus systemic therapy (55/96) was significantly associated with longer median OS (14.67 years) vs systemic therapy alone (9.65 years), with a HR of 0.479 (95% CI 0.232–0.988, p=0.04). 21/55 underwent surgery for multifocal disease after response to systemic therapy (TKI), 18/55 for unifocal disease after TKI response, 13/55 for unifocal progression with poor TKI response, and 3/55 for bleeding or obstruction.

Conclusion: Surgery plus systemic therapy had longer median OS than systemic therapy alone. This highlights the need for prospective studies to define optimal treatment and develop standardized care strategies.