Cancer risk slightly elevated in MS patients: 10-year study
Findings may be due to higher testing rates, researchers say
People with multiple sclerosis (MS) may have a slightly higher cancer risk than the general population, according to a recent study in France that reviewed a decade of data from more than 140,000 MS patients.
The risk of bladder, brain, cervical, and kidney cancer was significantly increased in MS patients compared with controls, but certain cancers were less common in those with MS, the study found.
The researchers suggested that the increased risk may be due to surveillance bias, meaning MS patients are more likely to have cancer detected than the general population because of increased testing, screening, or surveillance.
“People with MS undergo an increased number of tests to monitor MS, making it more likely to detect other diseases,” study author Emmanuelle Leray, PhD, said in an American Academy of Neurology press release. “We found an association between some types of cancer and MS which may have different explanations depending on a person’s age and the types of cancer.” The risk “was quite small,” Leray said.
The study, “Cancer Risk Among Patients With Multiple Sclerosis,” was published in Neurology.
Studies conflict
MS is an autoimmune disease marked by inflammation and damage to the brain and spinal cord. Depending on which parts of the nervous system are affected, symptoms can vary widely from person to person.
Several factors associated with MS, such as the inflammatory nature of MS and the immune-suppressing effects of many disease-modifying therapies (DMTs), which may allow emerging cancers to go undetected by the immune system, can increase the risk of cancer. Other cancer risk factors, such as elevated blood pressure and chronic lung disease, are also more common in MS patients.
Studies investigating the risk in MS have generated conflicting results. Some studies show an elevated risk, while others a lower risk or no risk at all. Differences in study populations and methodologies have been cited to explain such discrepancies.
The team of scientists at Rennes University reviewed 10 years of data in the French national healthcare database to compare the risk of cancer in MS patients with a matched group of people from the general population in France.
A total of 140,649 people with MS, of whom 70.8% were women, were matched with 562,596 people without MS based on factors such as sex, age, residence, and insurance status. Eligible participants were cancer-free for three years before the study and were then followed for an average of 7.6 years.
Over the follow-up period, 5.9% of people with MS and 5.7% of controls had a cancer diagnosis. Across both groups, the most common cancer types in women were breast, colorectal, lung, and cervical cancer. In men, prostate, lung, and colorectal cancer were the most common.
Overall, there was a 6% relative increase in the risk of cancer among people with MS. However, after stratifying the data by sex, a significantly higher risk (8%) was observed solely in MS women.
Looking at the different cancer types, the researchers found that MS patients had a 71% higher risk of bladder cancer, a 68% higher risk of brain cancer, a 24% higher risk of cervical cancer, and a 16% greater risk of kidney cancer. While a causal relationship could not be excluded, the team said, the higher rates of some of these cancers may be due to more frequent health monitoring.
Screening, treatments may be factors
“While our study found a higher risk for brain cancer, it may be due in part to earlier detection in those with MS since they regularly have brain scans which may detect cancers earlier, before a person has symptoms,” Leray said. “Frequent urinary tract infections in people with MS and the use of immunosuppressant drugs may contribute to their higher risk of bladder and cervical cancers.”
Conversely, MS patients had a 20% lower risk of prostate cancer, a 10% lower risk of colorectal cancer, and a 9% lower risk of breast cancer. But the team also showed that fewer MS patients underwent screening for breast, cervical, and colorectal cancers, which they said may partly explain the results.
“The lower risk for colorectal and breast cancers may be due in part to fewer people with MS getting screened for cancer in older age when they may be experiencing more MS symptoms,” Leray said. “More research is needed, including studies that look at more closely at how cancer screenings may play a role.”
The risk of death due to cancer was slightly higher (6%) in MS patients than in controls, although the difference failed to reach significance.
Due to a lack of data in the database, the study was unable to adjust for other factors that influence cancer risk, such as smoking, alcohol consumption, education, and income, the researchers wrote. Overall, “MS was associated with a small overall increased cancer risk compared with that in the general population,” they wrote. “The risk fluctuated depending on the type of cancer.”
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