Multiple Sclerosis and Cancer Risk: What Is the Relationship?

Compared with the general population, people with multiple sclerosis (MS) are at a slightly increased risk for cancer, according to study findings published in Neurology.

Researchers conducted a 10-year nationwide retrospective matched cohort study to compare the risk for cancer in people with vs without MS. Data from January 2012 to December 2021 were sourced from the Système National des Données de Santé. People with MS with no history of cancer in the previous 3 years were matched 1:4 with control patients based on age, sex, residence, insurance scheme, and cohort entry date. 2012 to 2021 was analyzed. The primary outcome was first incident cancer, defined as the date of the initial cancer treatment. Secondary outcomes included bladder, brain and central nervous system (CNS), breast, cervical, colorectal, kidney, lung, prostate, and skin cancer types. Fine and Gray models were used in statistical analyses.

A total of 140,649 people with MS were matched with 562,596 people without MS (mean age, 46.7; women, 70.8%; mean follow-up, 7.6 years). Incident cancer was identified in 8368 (5.9%) people with MS and 31,796 (5.7%) people without MS. Breast (35.8%), colorectal (10.1%), lung (6.9%), and cervical (6.9%) cancers were the most common among women, while prostate (24.3%), lung (12.7%), and colorectal (12.6%) cancers were the most common among men.

Cancer incidence was 799 and 736 per 100,000 person-years among people with and without MS, respectively. Overall, people with MS exhibited a slightly increased risk for cancer (hazard ratio [HR], 1.06; 95% CI, 1.03-1.08); however, this elevated risk was mostly observed in women (HR, 1.08; 95% CI, 1.05-1.11) vs men (HR, 1.01; 95% CI, 0.97-1.06).

People with vs without MS demonstrated higher risk for the following cancer types:

• Bladder: HR, 1.71; 95% CI, 1.54-1.89;
• Brain and CNS: HR, 1.68; 95% CI, 1.42-1.98;
• Cervical: HR, 1.24; 95% CI, 1.12-1.38; and,
• Kidney: HR, 1.16; 95% CI, 1.01-1.33.

In contrast, people with vs without MS demonstrated lower risk for the following cancer types:

• Prostate: HR, 0.80; 95% CI, 0.73-0.88;
• Colorectal: HR, 0.90; 95% CI, 0.84-0.97; and,
• Breast: HR, 0.91; 95% CI, 0.86-0.95.

For every cancer type, risk for cancer decreased with increasing age. The highest risk for cancer was observed among people with MS aged younger than 55 (HR, 1.20; 95% CI, 1.15-1.24), while the lowest risk for cancer was observed among those aged 65 and older (HR, 0.89; 95% CI, 0.85-0.94).

Study limitations include potential residual confounding and surveillance bias, inability to investigate the effect of clinical characteristics, and inability to adjust for long-term exposure to immune modulators.  

“More research is needed, specifically on the role played by ascertainment bias and screening adherence in the observed increased cancer risk in PwMS [people with MS],” the study authors concluded.

Disclosure: Multiple study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.