A new study has found that some cancers are slightly more common in people with multiple sclerosis (MS) than in people without MS. The study is published in the October 9, 2024, online edition of Neurology®the medical journal of the American Academy of Neurology. Types of cancer that have a slightly increased risk include bladder, brain, and cervical cancer. The study does not prove that MS increases a person’s risk of cancer. It only shows an association.
With MS, the body’s immune system attacks myelin, the white, fatty substance that insulates and protects the nerves. MS is chronic and can be unpredictable and disabling.
“People with MS undergo more tests to monitor MS, which makes it more likely to detect other diseases,” said study author Emmanuelle Leray, PhD, of the University of Rennes in France. “We found an association between some types of cancer and MS, which may have different explanations depending on the person’s age and the types of cancer. Overall, our study found that the increased risk of cancer was quite small.”
For the study, researchers reviewed 10 years of data in the French national healthcare database. The researchers identified 140,649 people with MS and compared them by factors such as age, sex and residence with 562,596 people without MS. All participants were cancer-free three years before the study. They were followed for an average of eight years.
During the study, 8,368 people with MS and 31,796 people without MS developed cancer.
The researchers determined that there were 799 cancers per 100,000 person-years in people with MS and 736 cancers per 100,000 person-years in people without MS. Person-years represent both the number of people in the study and the amount of time each person spends in the study.
The researchers found that people with MS had a 6% increased risk of developing any type of cancer regardless of their age, sex and residence. They also found that the risk of cancer was higher in those under 55 years of age and lower in people 65 years of age and older compared to people without MS.
The researchers then looked at the types of cancer. People with MS had a 71% increased risk of bladder cancer, a 68% increased risk of brain cancer, and a 24% increased risk of cervical cancer. However, they also had a 20% lower risk of prostate cancer, a 10% lower risk of colorectal cancer, and a 9% lower risk of breast cancer.
“While our study found an increased risk of brain cancer, it may be due in part to earlier detection in people with MS, as they have regular brain scans that can detect cancer earlier, before the person develops it.” symptoms,” Leray said. “Frequent urinary tract infections in people with MS and the use of immunosuppressive medications may contribute to an increased risk of bladder and cervical cancer.”
Leray added: “The lower risk of colorectal and breast cancer may be due in part to fewer people with MS undergoing cancer screening at older ages, when they may experience more MS symptoms. More research is needed, including studies that take a closer look at how cancer screening may play a role.”
A limitation of the study was that the researchers could not adjust for factors such as education, income, smoking and alcohol consumption, since this information was not available in the national database.
The study was supported by the Rennes Institute of Clinical Neurosciences and the EDMUS-ARSEP Foundation.