Epidemiology of Gallbladder Cancer in the Unites States

A Population-Based Study

Motasem Alkhayyat; Mohannad Abou Saleh; Thabet Qapaja; Mohammad Abureesh; Ashraf Almomani; Emad Mansoor; Prabhleen Chahal


Chin Clin Oncol. 2021;10(3):25 

In This Article



This is a retrospective, cohort analysis using a multiple health system research platform (Explorys Inc., Cleveland, OH, USA) developed by IBM Corporation, Watson Health.[23] Explorys include electronic health record (EHR) data of more than 50 million unique patients, from 26 healthcare systems with a total of 360 hospitals in the US from 1999 to date, representing approximately 15% of the population. Participating health systems are from all states and that provides a broad regional distribution of source population. Diagnoses, findings, and procedures are arranged into the Systematized Nomenclature of Medicine-Clinical Terms (SNOMED-CT) hierarchy[24] while prescription drug orders are mapped into SNOMED and RxNorm.[25] Access to Explorys is granted to participating healthcare systems. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). Source data are de-identified; therefore, Institutional Review Board (IRB) is not required. To keep patients' information confidentiality, Explorys rounds cell counts to the nearest 10. Explorys database has been validated previously in multiple fields including surgery and gastroenterology.[26–36]

Patient Selection

Using the Explorys platform, we identified a cohort of patients diagnosed with GBC between the period of December 1999 and December 2019. The study cohort (GBC) was identified by searching the database for a SNOMED-CT diagnosis of "primary malignant neoplasm of gallbladder" after excluding patients younger than 18 years old. The control group was then identified for those who have no GBC. Subsequently, a cohort of patients with first ever GBC diagnosis was identified between the period of December 2018 to December 2019 to calculate the incidence of GBC in the last year.

Risk Factors, and Predisposing Medical Conditions Associated With GBC

Sex, age, and race-based data were collected. Possible risk factors and predisposing medical conditions included smoking, alcohol abuse, obesity, diabetes mellitus (DM), family history of gastrointestinal (GI) cancer, primary sclerosing cholangitis (PSC), chronic viral hepatitis [hepatitis B virus (HBV) and hepatitis C virus (HCV)], chronic cholecystitis, and cholelithiasis was investigated using SNOMED-CT diagnostic codes.

Statistical Analysis

Demographics and associated diseases were characterized by descriptive statistics. The overall period prevalence was calculated by dividing the total number of individuals with GBC by the total number of individuals in Explorys [1999–2019], thus making sure that all patients in the denominator had an equal opportunity of being diagnosed with GBC. We also calculated the rate of new cases of GBC in the US in the past year [2018–2019] by dividing the number of individuals with first ever GBC diagnosis from December 2018 through December 2019 by the total number of individuals in Explorys in the past year in an attempt to provide a proxy estimate of annual incidence. A two-sided P value <0.05 was considered statistically significant, and all statistical analyses were performed using IBM SPSS Statistics version 25.