Multiple sclerosis outcomes after cancer diagnosis in people with recorded chemotherapy exposure: A real-world MSBase...

As more people with multiple sclerosis (MS) survive cancer, questions about MS management after cancer are increasingly relevant. This study aimed to describe post-cancer treatment patterns and MS outcomes in people with recorded chemotherapy exposure.

Using MSBase, we identified people with MS with cancer and chemotherapy exposure. Time to first relapse and 6-month confirmed disability progression (CDP) were analysed using Cox models with disease-modifying therapy (DMT) as a time-varying covariate. Outcomes were contextualised using 1:2 propensity-matched MS controls without cancer or chemotherapy.

In total, 363 individuals were followed for 2.8 years (median) after cancer. Older age at cancer was associated with lower relapse hazard (hazard ratio (HR) = 0.96 per year, p = 0.008), while DMT category was not. The DMT category was not associated with CDP. In matched analysis (256 vs. 505), relapse hazard was lower during the first year after cancer (HR = 0.30, p = 0.015) with no difference thereafter; CDP risk was similar (HR = 1.13, p = 0.60).

Post-cancer DMT category was not associated with relapse or CDP. Lower first-year relapse hazard, together with lower relapse hazard at older age, may provide cautious reassurance regarding early post-cancer inflammatory activity in similar clinical contexts, although the drivers of the first-year signal remain uncertain.