A. Singh1,2, B. S. Chitti3, C. E. Devoe1, G. Wernicke1, H. Rahman4, C. Sison4, and B. Parashar5; 1Department of Radiation Medicine, Northwell Health, Lake Success, NY, 2University of California, Los Angeles, Los Angeles, CA, 3Northwell, New Hyde Park, NY, 4Office of Academic Affairs, Northwell Health, New York, NY, 5Northwell, Lake Success, NY
Purpose/Objective(s): Gastrointestinal Stromal Tumors (GISTs) typically present as subepithelial neoplasms of the stomach with rarer occurrences in the small bowel & esophagus. Rarely treated with radiation, standard care includes imatinib and surgical resection. Due to GIST’s recent classification, it is unclear whether differences in patient outcomes exist across age. This analysis investigated GIST outcomes for patients aged =70 & <70 years using the Surveillance, Epidemiology, & End Results (SEER) Program. Materials/
Methods: Gastrointestinal stromal sarcoma (ICD-O-3 8936/3) data was obtained from SEER*STAT version 8.4.0.1 for the period 2000-2019. Codes pulled included age, sex, primary tumor localization, surgical status, & overall survival. Geriatric age was defined as =70 years. Statistical methods included univariate analysis using the KM survival estimate (95% confidence interval) for five-year survival & Log-Rank tests to observe statistical significance of the survival distribution. Multivariate analysis was used to determine the hazard ratio of death for geriatric patients when controlled for sex, stage, year of diagnosis, subsite, and surgery. Results: Of 13615, 13579 patients were included in analysis. The prevalence of GIST by subsite was the following: 7846 stomach, 3564 small intestine, 336 rectum, 84 esophagus, and 1875 in other sites. Radiation analysis was not done due to lack of treatment data. Analysis of patients regardless of surgical status with tumors in stomach, small intestine, and other subsites for non-geriatric and geriatric patients yielded 5-year survival rates of 79.9% (78.6%–81.2%), 80.4% (78.6%–82.1%), and 63.4% (60.5%–66.1%) versus 57.9% (55.8%–59.9%), 52.5% (49.1%–55.8%), and 38.4% (34.8%–42.0%) respectively. Non-geriatric and geriatric patient data yielded 5-year survival rates of 77.4% (76.4%–78.3%) and 53.3% (51.7%–54.8%) respectively (p<.0001). With respect to no surgery and surgery, the younger cohort yielded 5-year survival rates of 48.7% (45.8%–51.4%) and 83.7% (82.7%–84.7%) respectively (p<.0001), while geriatric data yielded rates of 29.3% (26.5%–32.1%) and 62.8% (60.9%–64.6%) respectively (p<.0001). Multivariable Cox PH regression model yielded a hazard ratio of 2.62 (2.48–2.77) for geriatric patients when adjusted for sex, year of diagnosis, stage, surgery and subsite (p<.0001). Conclusion: This was the first SEER analysis investigating GIST survival by subsite. We observed lower survival rates overall for geriatric patients in terms of 5-year survival. The estimated hazard of death in geriatric patients was observed to be 2.62 times higher compared to younger patients. Surgery appeared to enhance survival rates in both groups, suggesting surgery’s importance in overall GIST survival. Further GIST research is needed to confirm this strategy’s clinical effectiveness. Limitations include selection bias as this was a retrospective study. In addition, geriatric patients may have additional comorbidities.
