People with chronic conditions, such as diabetes or chronic obstructive pulmonary disease (COPD), spend enough time managing their symptoms and staying healthy. Should they worry that they might be at higher risk of developing cancer as well?
Some, but not all, epidemiologic studies have shown that people with some underlying chronic conditions may be at higher risk of certain types of cancer compared with those who do not have such conditions. For instance, a systematic review concluded that people with pancreatitis have a higher risk of developing pancreatic cancer compared to those without the disease, although the magnitude of relative risk varied greatly between 1.5 and 29 times. Also, ulcerative colitis has been associated with a 2.4-fold increased risk of colorectal cancer in a meta-analysis of eight population-based cohort studies. Results from another meta-analysis indicate that diabetes is associated with a 1.23-fold increased risk of breast cancer, and the elevation of risk is higher among postmenopausal women.
Some Conditions Associated With Risk Reduction
In contrast, several chronic diseases have been associated with a reduction in the risk of cancer. The systematic review of pancreatic cancer mentioned above also showed that in 8 out of 11 studies, a 23%-61% decrease of pancreatic cancer incidence was observed among those with allergies. A lower risk of some cancers has also been found in systemic lupus erythematosus (SLE) patients. In 2011, the British Journal of Cancer published a meta-analysis pooling data from 47,325 SLE patients revealed a 24% lower risk of breast cancer, 29% lower risk of endometrial cancer, and 34% lower risk of ovarian cancer.
Possible Underlying Mechanisms
The biological mechanisms underlying the development of cancer among individuals with chronic diseases are poorly understood. In some cases, the underlying condition itself may be a risk factor for a certain cancer (e.g., pancreatitis and pancreatic cancer). It is also possible that the treatments (e.g., immunosuppressant therapies) may affect the risks of developing cancer. Moreover, environmental exposures, lifestyle factors, and genetic susceptibility may be risk factors for both the chronic disease and specific forms of cancer (e.g., smoking may increase the risk of both COPD and lung cancer).
Over Age 65 Population Means More Chronic Diseases
It is estimated that the number of people over the age of 65 in the U.S. will grow from 39.6 million in 2009 to more than 72 million by 2030, and most people in this age group have one or more chronic diseases. Therefore, understanding the association between chronic diseases and cancer risk is becoming even more important. There are numerous studies that need to be done to fully understand the epidemiology and natural history of chronic diseases in relation to cancer incidence, and ultimately assist clinicians, patients, and policy makers to develop prevention, screening, and treatment interventions that can target high-risk groups.
Available Research Resources
The Epidemiology and Genomics Research Program’s (EGRP) Website provides links to research resources and NIH funding opportunities that may be useful:
- National and State Cancer Registries
- Cancer Epidemiology Cohorts
- Pharmacoepidemiology and Healthcare Databases
For additional information about research opportunities, please contact EGRP’s Clinical and Translational Epidemiology Branch (CTEB) with questions on studies and grant applications.
Yingjun (Grace) Zhou, M.S., is a Cancer Research Training Award Fellow in EGRP’s Clinical and Translational Epidemiology Branch. In this capacity, she is involved in projects related to cancer risk prediction models, pharmacoepidemiology, and pharmacogenomics. Prior to joining EGRP, Grace was a Special Volunteer in NCI’s intramural Division of Cancer Epidemiology and Genetics where she built risk prediction models using modern machine learning approaches and analyzed microbiome data. Grace received her Master of Science in epidemiology and biostatistics from George Mason University and Bachelor of Science in biochemistry from the Hunan Teachers University in China.