Do people with multiple sclerosis have an increased risk of cancer?

A new study has found some cancers to be slightly more frequent in people with multiple sclerosis than in people without multiple sclerosis. The study is published in the October 9, 2024, online issue of Neurology^®, the medical journal of the American Academy of Neurology. Types of cancers found to have a small increased risk include bladder, brain, and cervical cancers. The study does not prove that multiple sclerosis increases a person’s risk of cancer. It only shows an association.

With multiple sclerosis, the body’s immune system attacks myelin, the fatty, white substance that insulates and protects the nerves. Multiple sclerosis is chronic and can be unpredictable and disabling.

“People with multiple sclerosis undergo an increased number of tests to monitor multiple sclerosis, making it more likely to detect other diseases,” said study author Emmanuelle Leray PhD, of Rennes University in France. “We found an association between some types of cancer and multiple sclerosis which may have different explanations depending on a person’s age and the types of cancer. Overall, our study found the increased risk of cancer was quite small.”

For the study, researchers reviewed 10 years of data in the French national healthcare database. Researchers identified 140,649 people with multiple sclerosis and matched them for factors such as age, sex, and residence to 562,596 people without multiple sclerosis. 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 multiple sclerosis and 31,796 people without multiple sclerosis developed cancer.

Researchers determined there were 799 cancers per 100,000 person-years for people with multiple sclerosis and 736 cancers per 100,000 person-years for people without multiple sclerosis. Person-years represent both the number of people in the study and the amount of time each person spends in the study.

Researchers found people with multiple sclerosis had a 6% increased risk of developing any type of cancer regardless of age, sex, and residence. They also found cancer risk was higher in those under 55 and lower in people 65 and older when compared to people without multiple sclerosis.

Researchers then looked at cancer types. People with multiple sclerosis had a 71% increased risk for bladder cancer, a 68% increased risk for brain cancer and a 24% increased risk for 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 a higher risk for brain cancer, it may be due in part to earlier detection in those with multiple sclerosis since they regularly have brain scans which may detect cancers earlier, before a person has symptoms,” said Leray. “Frequent urinary tract infections in people with multiple sclerosis and the use of immunosuppressant drugs may contribute to their higher risk of bladder and cervical cancers.”

Leray added, “The lower risk for colorectal and breast cancers may be due in part to fewer people with multiple sclerosis getting screened for cancer in older age when they may be experiencing more multiple sclerosis symptoms. More research is needed, including studies that look at more closely at how cancer screenings may play a role.”

A limitation of the study was that researchers were unable to 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.

Source: News Release
American Academy of Neurology
October 9, 2024