A large-scale French study found patients with multiple sclerosis had a slightly elevated overall cancer risk compared to the general population, with significant variations by cancer type, age group, and sex.

The retrospective cohort study, published in Neurology, analyzed data on 140,649 multiple sclerosis (MS) patients and 562,596 matched controls from the French national health insurance database over from 2012 to 2021.

The study found overall cancer incidence was 799 per 100,000 person-years in MS patients vs. 736 per 100,000 person-years in controls, but cancer risk was increased in MS patients younger than 55 years but decreased in those 65 and older. Bladder cancer risk was markedly elevated in MS patients, especially in women. Brain/CNS, cervical, and kidney cancer risks also were increased among MS patients. However, prostate, breast, and colorectal cancer risks were decreased in MS patients. Crude cancer mortality rates were 2,378 per 100,000 person-years for MS patients vs. 2,381 for controls, with an adjusted incidence rate ratio of 1.06.

MS patients exhibited lower participation rates in national cancer screening programs, especially those aged 65 and older. The gap in screening rates widened with age. For example, in the 65-74 age group, breast cancer screening rates were 50.5% for MS patients vs 64.4% for controls.

The study utilized data from the Système National des Données de Santé (SNDS), which covers approximately 99% of the French population. MS patients were identified based on long-term disease status, hospitalizations, and disease-modifying therapy reimbursements. Cancer cases were identified through long-term disease status, hospitalizations, and cancer-specific treatments.

Researchers employed Fine and Gray models to calculate hazard ratios, accounting for death as a competing risk. They also analyzed cancer screening participation rates for breast, cervical, and colorectal cancer.

The study's strengths included its large sample size, long follow-up period, and use of nationwide data. Limitations included potential surveillance bias due to more frequent healthcare utilization by MS patients and the inability to adjust for lifestyle factors or MS clinical characteristics.

Conflict of interest disclosure can be found in the study.