Among more than 50,000 Canadians with MS, the rates of breast and colorectal cancers were not increased compared with people without MS. However, the rates of bladder cancer may be increased. More research is needed to confirm these findings.
Multiple sclerosis involves an abnormal immune response that damages the brain and spinal cord (central nervous system). Since some emerging cancers can be eliminated by the immune system, there is a chance that people with MS could have an increased risk for cancer. Over the years, studies have examined the risk for cancer in people with MS. While overall, the results of these studies have been inconclusive, there are reports of an increased risk of breast and colorectal cancers in people with MS.
To explore these possible risks, the investigators examined the health records of 53,984 people with MS and 266,920 people without MS across two Canadian provinces. Researchers also used cancer registries to estimate incidence of breast, colorectal, and bladder cancer, among others.
They found no increase in the incidence (rate of new cases) of breast cancer and colorectal cancer in people with MS compared to people without MS.
The investigators found that people with MS had possible increased rates of bladder cancer than people without MS. More research is needed to confirm this increase, since people with MS tend to have urinary symptoms and treatments that themselves can be risk factors for bladder cancer. The authors point out the need for guidelines for monitoring urinary symptoms in people with MS.
One possible study limitation was that the researchers were unable to account for differences in health-affecting behaviors such as smoking, diet, physical activity, or the use of specific MS disease-modifying therapies.
Learn more about Coping with dual diagnoses and keeping up with preventive care recommendations.
“Cancer incidence and mortality rates in multiple sclerosis: A matched cohort study” by Ruth Ann Marrie, MD, PhD (University of Manitoba, Winnipeg), Patti A. Groome, PhD (Queen’s University, Kingston, Ontario), and colleagues is published in Neurology (published online, November 25, 2020). This study was funded by the MS Society of Canada.