The HCUP-NIS contains data from 1,050 hospitals and represents a 20% stratified sample of US community hospitals (9). Since the HCUP-NIS is a discharge-level database, each line represents a single unique hospitalization. Institutional Review Board approval is not required when using this database, since it is made available to researchers in a de-identified format. Study design and sample A retrospective cross-sectional design was used for this study. Discharges with LOS greater than 365 days or total charges greater than $1 million were excluded from the analysis. Patients hospitalized with any listed diagnosis of GISTs were identified using the International

Inhibitors,research,lifescience,medical Inhibitors,research,lifescience,medical Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes including 171.5, 171.8, 171.9, 215.1 or 238.1 (10). A control group consisting of patients without any diagnosis of GISTs or other cancers was identified. Cases and controls were matched based on age and gender in a 1:4 ratio using a greedy match algorithm (11). Statistical medical Analysis All analyses were performed using PROCSURVEY procedures in Statistical Analysis System (SAS) version 9.2 to account for the

complex sampling design of the HCUP-NIS. Hospitalization rates for GISTs were reported by patient-, Inhibitors,research,lifescience,medical hospital-, and discharge-level characteristics. Rates were calculated by dividing the number of weighted hospitalizations associated with GISTs in each category by the total number of hospitalizations in that category. In addition, common comorbid diagnoses and procedures performed among patients with GISTs were assessed. Hospitalization Inhibitors,research,lifescience,medical characteristics among patients with GISTs were compared to Inhibitors,research,lifescience,medical the control group using χ2 test and t-test. Linear regression (PROC SURVEYREG) was used to determine the factors predicting total charges among patients with GISTs. Factors predicting mortality among patients with GISTs were determined using logistic regression (PROC SURVEYLOGISTIC). Results reported in the study are weighted estimates. Results Table 1 describes the hospitalization

rates for GISTs and compares the patient-, hospital-, and discharge-level characteristics among patients with and without a diagnosis of GISTs. In 2009, there were a total of 14,562 hospitalizations among patients with GISTs in the US. The overall hospitalization STK38 rate of patients with GISTs was 44/100,000 admissions. In terms of patient-level characteristics, the highest rates for GISTs were among patients aged 50-64 years, males, having household income of $63,000 or more, and with private insurance, respectively. As per hospital-level characteristics, rates were the highest for hospitalizations that took place in small hospitals, urban hospitals, hospitals located in the South, and teaching hospitals, respectively.