Use of Disease-modifying Therapies and Risk of Cancer in People Living with MS


This population-based MS Canada-funded study investigated whether use of disease-modifying therapies (DMTs) is associated with cancer risk in people with MS. A team of Canadian researchers looked at over 14,000 cases of MS in Alberta over a ten-year period. Over 40% of these cases have taken at least one DMT. When compared to the general population, the researchers found no difference in cancer risk among people with MS, including those exposed to at least one DMT. The main finding is an age-related effect of DMTs on cancer risk, with a protective effect at younger ages and an increased risk at older ages when compared to people with MS not exposed to DMTs. Real-world studies like this one are needed to inform people living with MS and healthcare providers of potential health risks associated with DMT exposure.  


This population-based study aimed to understand whether exposure to DMT is associated with an increased risk of cancer in people with MS.

  • The researchers looked at 14,313 cases of MS in Alberta between 2008 to 2018 using health administrative data. 
  • During the study, over 40% of these individuals have taken at least one DMT (or have been exposed to a DMT). DMTs were looked at in these groups: 
    • modulating DMTs (39.6% were exposed to these DMTs) e.g. dimethyl fumarate, glatiramer acetate, interferon beta, minocycline, teriflunomide
    • sequestering DMTs (6.9% were exposed to these DMTs) e.g. fingolimod, natalizumab
    • depleting DMTs (1% were exposed to these DMTs) e.g. alemtuzumab, cladribine, cyclophosphamide, mitoxantrone, ocrelizumab, rituximab.


The researchers found that:

  • When compared to the general population, cancer risk for people with MS was similar.
  • There was also no difference in cancer risk for those taking DMTs compared to the general population. 
    • The most common cancers diagnosed among people with MS were breast, lung, prostate, colon, and endometrium. 
  • When they compared people with MS who had been exposed to a DMT to those who had not been exposed to a DMT, they found a difference in cancer risk that is associated with age. 
    • There was a protective effect for younger ages, and an increased cancer risk for those 62 years of age and older when exposed to any DMT. 
    • DMT exposure and this analysis did not take into account duration or dose of treatment.
    • Note that this result should be taken with caution due to the small sample size and short duration of follow-up.


Further research is needed to clarify whether the association found between older age and DMT exposure is indeed the case and a direct cause of the increased risk of cancer. Additionally, further studies with larger populations and longer follow-up will be needed to determine whether different types of DMTs (such as sequestering or depleting DMTs) influence cancer risk. 

These types of real-world studies are needed to understand the long-term health risks of DMTs for MS. Understanding the long-term risks of DMTs improves clinical care and supports people living with MS make informed decisions about their health. 


Jamie Greenfield a, Luanne M. Metz a, Amir Khakban b, Elisabet Rodriguez Llorian b, Kristina D. Michaux b, Anthony Traboulsee c, Jiwon Oh d, Penelope Smyth e, Larry D. Lynd b f, Andrew G.M. Bulloch g, Jeanne V.A. Williams g, Scott B. Patten g, CanProCo Study Group. Cancer risk, disease-modifying therapy, and age in multiple sclerosis: A retrospective population-based cohort study. Multiple Sclerosis and Related Disorders. (2023). Link to article – here.