Small Increased Cancer Risk Seen in People With MS

People with multiple sclerosis (MS) had an increase in cancer risk compared with matched controls from the French general population, a retrospective study found.

A small increased risk for cancer was seen in the MS group versus controls (HR 1.06, 95% CI 1.03–1.08), according to Emanuelle Leray, PhD, of Rennes University in France. and co-authors.

However, after stratification by sex, the higher risk was observed only in women (women HR 1.08, 95% CI 1.05–1.11; men HR 1.01, 95% CI 0.97–1.06), they reported in Neurology.

Compared with controls:

• MS patients showed an increased risk for bladder (HR 1.71, 95% CI 1.54–1.89), brain (HR 1.68, 95% CI 1.42–1.98), cervical (HR 1.24, 95% CI 1.12–1.38), and kidney cancers (HR 1.16, 95% CI 1.01–1.33).
• MS patients had a reduced risk for prostate (HR 0.80, 95% CI 0.73–0.88), colorectal (HR 0.90, 95% CI 0.84–0.97), and breast cancers (HR 0.91, 95% CI 0.86–0.95).
• Cancer risk was higher in MS patients younger than 55 years (HR 1.20, 95% CI 1.15–1.24) but decreased in those 65 years and older (HR 0.89, 95% CI 0.85–0.94).
• There were fewer people in the MS cohort who received cancer screening at any of three French screening programs.

Leray and co-authors suggested that the increased cancer risk observed in younger MS patients might reflect varying generational screening practices and risk factors.

"There was a very large increase in the incidence of bladder cancer in both sexes and all age subgroups," they pointed out. "The incidence of cervical and kidney cancer was also increased, but not that of lung cancer. The incidence of prostate, breast, and colorectal cancer was decreased, partially because of lower cancer screening in the older MS age groups."

"More research is needed, specifically on the role played by ascertainment bias and screening adherence in the observed increased cancer risk in people with MS," the researchers recommended.

Leray and colleagues conducted a nationwide retrospective matched cohort study in France with data from the national health care database to determine the time to the first incident cancer. They compared people with MS (n=140,649, with 8,368 cancer cases) with matched controls (n=562,596, with 31,796 cancer cases) from 2012 to 2021.

Participants had no history of cancer in the 3 years before inclusion, and incident cancer during follow-up was identified through means including hospitalizations, chemotherapy, radiotherapy, or cancer–specific drug reimbursements, and other records.

The MS cohort had 70.8% women and the mean age at entry was 46.7 years, with a mean age at MS identification of 40.5 years. The control group was matched to the MS cohort on age, sex, residence, insurance scheme, and cohort entry date. Participants were followed for 7.6 years.

The MS and control groups differed in rates of screening through three French programs for breast (64.9% vs 71.6%), cervical (63.2% vs 64.1%), and colorectal cancers (34.6% and 36.9%; P<0.001 for all).

"Cancer screening tended to decrease with age in people with MS but not in controls, leading to a widening of the gap between the two groups," the researchers noted.

Other factors also may have influenced results, they noted. "Cancer risk was slightly increased in people with MS, particularly for urogenital cancers, possibly due to surveillance bias," Leray and colleagues wrote.

People with MS use health care services more often than the general population, which may have resulted in better identification of cancer cases and overestimation of the cancer risk in MS, they noted. "This issue is particularly relevant for the observed 68% risk increase in brain and CNS [central nervous system] cancers," Leray and co-authors noted, a finding consistent with previous studies. "This is further suggested by the 24% decrease in cancer mortality rates in MS for this cancer type."

The increase in bladder cancer remained significant across all subgroups and was more pronounced in women, the researchers added. Urological complications with MS like chronic urinary tract infection and indwelling catheterization may increase risk, they noted. Long-term cyclophosphamide treatment and lifestyle factors may also contribute.

"This remains a large increased risk that must be taken into account when providing preventive care to people with MS, and potential causes need to be further investigated," they emphasized.

Study limitations included data that were not originally collected for epidemiologic purposes and the use of algorithms to identify different diseases, the researchers said.

The administrative data lacked information about demographic and risk factors, so those variables — along type of MS, disability level, or cancer stage at diagnosis — were not included in the analysis.

This study was funded by the Institut des Neurosciences Cliniques de Rennes and the EDMUS-ARSEP Foundation.

Leray reported consulting and lecture fees or travel grants from Alexion, Biogen, Merck, Novartis, Roche, and Sanofi, not related to the submitted work.

Pierret C, et al "Cancer risk among patients with multiple sclerosis: a 10-year nationwide retrospective cohort study" Neurology 2024; DOI: 10.1212/WNL.0000000000209885.