Clinicopathological features and survival outcomes in patients with high microsatellite instability small intestine cancers: A National Cancer Database analysis.

Abstract

e15726 Background: Small intestine cancer (SIC) is a rare malignancy, accounting for less than 5% of all gastrointestinal cancers. The incidence of SIC has been increasing in recent decades. Microsatellite instability (MSI) is identified in approximately 10-15% of SIC cases, which has implications for prognosis and treatment. Prognosis and treatment strategies for SIC are often extrapolated from studies on colorectal cancer due to the rarity of the disease and the lack of specific clinical trials. Methods: The National Cancer Database (NCDB) Public Use File (PUF) for SIC was utilized to identify 394 adult patients diagnosed with tumors localized to the small intestine between 2004 and 2022, with high MSI (identified using CS site-specific factor 5, codes 050 and 060). Demographic information was obtained, and Kaplan-Meier analysis was used to analyze overall survival. A Cox regression model was applied to obtain hazard ratios and assess the association of patient characteristics and treatment methods with survival. SPSS version 30 was used to perform all analyses. Results: The majority of SIC patients were male (57.6%), white (78.4%), with a median age at diagnosis of 63. 63.5% of patients were treated at academic centers. The primary sites of disease were as follows: duodenum (38.1%), ileum (18.8%), jejunum (25.4%), overlapping lesions (1.8%), and unspecified sites (16%). Adenocarcinoma represented 91.9% of all histological types. Of the patients, 56.8% had moderate or well-differentiated tumors, and 36.5% had poorly differentiated tumors. Most patients presented at stage II (42.4%), followed by stage III (27.9%), stage I (7.1%), and stage IV (10.7%). Most patients received surgery (90.6%), chemotherapy was given to 43.1%, immunotherapy to 5.3%, and only 4.1% received radiation treatment. The median overall survival (OS) was 124.7 months; for stage III: 105 months, and for stage IV: 13 months. Median OS was not reached for stages I and II (log-rank comparison p < 0.001). In the Cox regression model, factors associated with increased mortality (p < 0.001) included increasing age at diagnosis (HR 1.1), stage IV (HR 2.8), and lymphovascular invasion (HR 1.6). Factors associated with decreased mortality (p < 0.05) included receipt of chemotherapy (HR 0.6) and immunotherapy (HR 0.5). Conclusions: This is the first study to analyze MSI-H SIC using the NCDB. Understanding patient characteristics and overall survival is essential for improving outcomes in this rare malignancy.