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News|Articles|April 6, 2026

Disease-Modifying Therapy Use Decreased in Patients With MS Diagnosed With Cancer

Fact checked by: Rose McNulty
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Key Takeaways

  • Multinational administrative cohorts (France, British Columbia) matched incident cancer cases with MS 1:2 to controls, evaluating MS-related care utilization across two years before and after first cancer-related event.
  • Neurologist visit frequency was modestly higher among cancer cases than controls but declined over time in both settings, with no meaningful pre/post-cancer change in incident rate ratios.
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Despite decreases in therapy use, hospitalizations for multiple sclerosis and neurologist visits were not affected significantly.

Patients with multiple sclerosis (MS) who were diagnosed with cancer had a sharp decline in the use of disease-modifying therapies (DMTs) after their diagnosis, according to a new study published in the Multiple Sclerosis Journal.1 There were no major impacts on hospitalizations or neurologist visits in these patients despite this decline, however.

Life expectancy is increasing in patients with MS across North America,2 which has led to the increased prevalence of comorbidities in this population, including cancer. The effect that cancer has on care for MS has not been as studied,1 including how it affects DMT adherence. This study aimed to evaluate how cancer affects care related to MS and the use of DMT in a retrospective cohort study.

The data for this study came from France and the province of British Columbia (BC) in Canada, using population-based health administrative data. Electronic health records that included sociodemographic data and the use of health services. Admission and discharge dates were both included for each hospitalization along with a diagnostic code. All medical procedures were recorded in France, and patients can acquire long-term disease status for a chronic disease that requires long or expensive treatments.

An algorithm was used to identify patients with MS based on diagnostic codes or prescription fills for DMT in BC. Patients with MS were identified through hospitalizations, drug reimbursements, or long-term disease status in France. The study included 2 population-based cohorts with data available from January 1, 1991, to March 31, 2020, in BC and from January 1, 2009, to December 31, 2021, in France. Cases were any patients with MS aged 18 years or older who had an incident case of cancer. The follow-up period was the 2 years before and after the first cancer-related event.

Health care use that was related to MS was based on neurologist visits, hospitalizations due to MS, and the use of DMT. The use of DMT was defined as having filled prescriptions for DMTs that were specific to MS as well as other non-specific or off-label drugs that can be used to treat MS.

There were 20,706 patients with MS who were included in the study, of which 6902 were cases of MS; they were matched 1:2 to 13,804 controls. Most of the participants were women (71.6% from France, 75.9% from BC). The mean (SD) age of the participants was 58.6 (12.5) years and 55.9 (11.6) years in France and BC, respectively. Breast, prostate, and colorectal cancer were the most common forms of cancer.

Patients with MS saw a neurologist more often than controls in both France (75.1% vs 72.7%) and BC (72.0% vs 68.7%), though both groups saw a decrease over time. Patients with MS had a slightly higher visit rate to the neurologist both before and after cancer. Incident rate ratios (IRR) did not differ before and after cancer. Hospitalization rates also did not differ between cases and controls before and after cancer.

However, fewer patients with MS taking a DMT for their condition received those DMTs in BC compared with France (13.4% vs 36.0%). Fewer patients with MS were on DMT after cancer compared with their controls (post-cancer OR, 0.48; 95% CI, 0.25-0.94). Cancer was found to have a negative effect on the use of DMTs (slope ratio, 0.36; 0.19-0.94), which remained after including off-label drugs. All time periods and all age groups were found to have the same association.

There were some limitations to this study. Population-based studies can have limited clinical data or data on lifestyle. The stage of the cancer and the severity of the cancer were not available. Minor misclassification is possible due to the DMT exposure windows being based on filled prescriptions.

“This study offers valuable insights into how the diagnosis of cancer affects MS neurological care and treatment decisions, yielding reassuring and consistent results across 2 regions on separate continents,” the authors concluded. “As the MS population grows and ages, this issue is becoming increasingly relevant.”

References

  1. Pierret C, Androdias G, Lebrun-Frenay C, et al. Impact of cancer on multiple sclerosis–related healthcare and disease-modifying drug use: a multinational cohort study. Mult Scler. Published online April 5, 2026. doi:10.1177/13524585261437966
  2. Life expectancy and MS. MS Society. Accessed April 6, 2026. https://www.mssociety.org.uk/about-ms/what-ms/life-expectancy-and-ms

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