Abstract 753: Associations of inflammatory bowel disease and subsequent cancers in the United States elderly population
Authors: Wang Jeanny , D'Arcy Monica , Engels Eric , Song Minkyo 
Published: July 2021

Introduction: The risk for cancer may be elevated in patients with inflammatory bowel disease (IBD) due to chronic inflammation caused by IBD and/or immunosuppressive treatments. A comprehensive investigation of cancer as a complication of IBD in elderly patients is needed, as this population has a high background risk of cancer and are underrepresented in IBD studies.

Methods: We performed a case-control study using Surveillance Epidemiology and End Results-Medicare linked data. Cancer cases (N=1,986,735) included all patients aged 66-99 with a first invasive neoplasm diagnosed in 1992-2015. Cancer-free controls (N=200,000) were randomly selected from Medicare and matched by sex, age, and selection year. Medicare claims containing ulcerative colitis (UC) or Crohn's disease (CD) diagnosis codes occurring at least one year prior to selection were used to identify IBD patients. We estimated odds ratios (OR) and 95% confidence intervals (CI) with logistic regression, adjusting for the matching factors, race, and the average number of physician visits per year. A Bonferroni-corrected threshold of significance was defined as p &lt; 0.0003 for 156 tests. Colorectal cancer analyses were further adjusted for the average number of colorectal cancer screens per year occurring at least one year before selection.

Results: IBD, CD, and UC were present in 0.80%, 0.33%, and 0.53% of cancer cases and in 0.76%, 0.30%, and 0.52% of controls, respectively. Out of 52 cancers examined, IBD was significantly associated with cancers of the small intestine (OR=2.53; 95% CI=2.14-2.99), intrahepatic (1.93; 1.48-2.52) and extrahepatic bile ducts (1.73; 1.37-2.19), rectum (1.67; 1.43-1.94), colon (1.20; 1.10-1.31), and lung (1.14; 1.07-1.23). For hematological malignancies, IBD was significantly associated with myelodysplastic syndrome (MDS) (OR=1.45; 95% CI=1.28-1.65) and diffuse large B-cell lymphoma (DLBCL) (1.28; 1.13-1.46). An inverse association was observed for IBD and cancer of the uterus (0.72; 0.62-0.83). CD was associated with cancers of the small intestine (OR= 4.21; 95% CI= 3.40-5.22), myelodysplastic syndrome (1.74; 1.44-2.11), rectum (1.60; 1.1.26-2.03), and lung (1.29; 1.16-1.43) and. UC was associated with cancers of the gastrointestinal system: intrahepatic bile ducts (1.94; 1.41-2.67), rectum (1.88; 1.57-2.25), and colon (1.38; 1.25-1.53).

Conclusions: Our large population-based analysis evaluating a comprehensive range of cancers found IBD significantly associated with increased risk for cancers of the small intestine, biliary tract, colorectum, and lung. IBD was also associated with DLBCL and MDS. Positive associations with IBD and cancers of the gastrointestinal system may reflect complications of chronic inflammation, while associations with DLBCL and MDS may reflect the effect of immunosuppressive medications.

Citation Format: Jeanny Wang, Monica D'Arcy, Eric Engels, Minkyo Song. Associations of inflammatory bowel disease and subsequent cancers in the United States elderly population [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 753.