People with multiple sclerosis (MS) who developed solid cancer experienced more clinical and radiographic disease activity around the time of cancer diagnosis than matched people with MS without cancer, according to findings from an Italian multicenter retrospective cohort study presented at MSToronto2026.

Researchers included 148 people with MS who developed solid cancer and 148 age- and sex-matched controls without cancer from 4 MS centers in Italy. MS activity was assessed during the 12 months before and after the index date using clinical relapses and new T2 or gadolinium-enhancing lesions.

Annualized relapse rates did not differ between groups during the year before enrollment (P=.777).

Key results included the following:

  • During the peri-index period, 20.7% of participants with cancer experienced at least 1 clinical relapse, compared with no relapses among controls (P<.001).
  • New T2 or gadolinium-enhancing lesions occurred more frequently among participants with cancer (P<.001).
  • After adjustment for disease-modifying therapy class and MRI region, participants with cancer had a higher lesion accrual rate than controls (incidence rate ratio, 5.91; 95% CI, 2.46-14.19; P<.001).
  • Among participants with cancer, older age and more advanced cancer stage were each associated with a lower composite risk of MS reactivation (P=.006 for both).
  • Findings remained consistent after excluding 35 participants who changed disease-modifying therapy class.

The retrospective design does not establish that cancer caused the observed increase in MS activity. The findings identify an association between cancer diagnosis and greater clinical and MRI activity that may be relevant when monitoring people with MS who develop malignancy.

Source

Di Gianvito V, Ponzano M, Frau J, et al. Cancer as a disease modifier in multiple sclerosis: an Italian multicenter matched cohort study. Paper presented at: MSToronto2026; October 20-23, 2026; Toronto, ON, Canada.