Cancer risk and mortality in patients with multiple sclerosis in Finland: a retrospective population-based cohort study
Anna Maunula, Sini M Laakso, Matias Viitala, Marja-Liisa Sumelahti, Sari AtulaBackground
Risk and outcome of cancer for patients with multiple sclerosis (pwMS) remain disputed. We aimed to investigate cancer incidence and cancer-specific mortality rates in pwMS compared with a matched population sample.
Methods
In this nationwide retrospective population-based study, pwMS in Finland were identified from the National MS-registry and the Care Register for Healthcare and matched to up to five population controls with data from 1974 until 2021. Standardised incidence rates, relative risks and HRs were calculated for all cancers and cancer subtypes utilising the Finnish Cancer Registry. A standardised mortality ratio (SMR) for cancer-specific causes was calculated, and survival analysis using a cumulative incidence function with a competing risk model of the probability of death was performed.
Results
We found 16 815 MS patients and selected 80 950 controls. Follow-up time was a median of 15.2 (8.2–22.9) years for pwMS and 17.5 (9.5–26.0) years for controls. Mean age at the diagnosis of first cancer was lower in pwMS (61.4y; SD 11.89) compared with controls (64.5y; 12.53; p<0.001). PwMS had a similar risk for all cancers (SIR 0.96; 95% CI 0.90 to 1.03) compared with controls. For males, the risk was lower (SIR 0.83; 95% CI 0.72 to 0.94). SMR showed that cancer-specific mortality for all cancers was similar to controls (1.02; 95% CI 0.93 to 1.11).
Conclusions
Patients with MS have a similar risk for cancer and equal cancer-specific mortality compared with population controls. However, pwMS are diagnosed with cancer at a younger age compared with controls.