15-year survivorship in patients with metastatic gastrointestinal stromal tumors.

Abstract

11525 Background: Prior studies of metastatic gastrointestinal stromal tumors (mGIST) have largely focused on 5-year survival when evaluating long-term outcomes, but factors underlying longer-term survival remain less understood. This retrospective study aimed to identify factors associated with 15-year survivorship in patients with mGIST. Methods: Patients with mGIST treated at Oregon Health & Science University between 2003-2023 were identified from the Knight Cancer Registry. Data were abstracted through manual chart review. Patients were categorized into two cohorts: those who died before 15 years of follow-up, and those who survived ≥15 years following mGIST diagnosis. Chi-square and independent samples t-tests were performed to compare clinicopathologic variables between the two groups. Results: Of the 111 eligible patients (66 male [59.5%]; 45 female [40.5%]; median [IQR] age, 57 [46-71] years, 88.3% Non-Hispanic White), nineteen (17.1%) survived ≥15 years after mGIST diagnosis. Factors associated with 15-year survival were younger age at metastatic diagnosis (44 [32-56] vs. 60 [53-73], p<0.001) and metastasectomy (n=12 [63.2%] vs. 27 [29.3%], p=0.008). Most (68.4%) patients who underwent metastasectomy did so before they developed resistance to imatinib. Patients who underwent metastasectomy before developing resistance were more likely to achieve 15-year survival, however, this association was not observed in those who underwent metastasectomy after imatinib resistance. Patients who underwent metastasectomy also experienced a longer median time to imatinib resistance relative to those who did not (55 months vs. 23 months, p=0.001). Conclusions: This retrospective study supports that younger age at metastatic diagnosis and metastasectomy before the development of imatinib resistance are factors associated with 15-year survivorship in patients with mGISTs. These findings suggest that surgical resection of metastases in select patients may prolong the duration of imatinib response and potentially improve long-term outcomes. Tumor and treatment factors associated with 15-year survivorship in mGIST. Variable Total (n=111) 15-year nonsurvivors (n=92) 15-year survivors (n=19) p-value Synchronous metastases 53 (47.7%) 43 (46.7%) 10 (52.6%) 0.64 Metachronous metastases 58 (52.2%) 49 (53.3%) 9 (47.4%) 0.7 Primary tumor size, cm (median, IQR) 8 (5.5-11.5) 8 (5.5-12) 8.1 (5.7-10.5) 0.79 Underwent metastasectomy 57 (51.4%) 42 (45.7%) 15 (78.9%) 0.008 Underwent metastasectomy before imatinib resistance 39 (35.1%) 27 (29.3%) 12 (63.2%) 0.04 Underwent metastasectomy after imatinib resistance 15 (13.5%) 12 (13.0%) 3 (15.8%) 0.75 Time to metastasectomy, months (median, IQR) 6 (16-42.5) 16 (6-41) 9 (4-86) 0.84 Development of imatinib resistance 69 (62.2%) 60 (65.2%) 9 (47.4%) 0.14 Time to imatinib resistance, months (median, IQR) 42 (22-81) 35.5 (20.5-63.3) 125.5 (95-149.5) <0.00001