Decreased risk of cancer in multiple sclerosis patients and analysis of the effect of disease modifying therapies on cancer risk

Background Although dysimmunity is considered an important link between multiple sclerosis (MS), family history and cancer risk, their relationship to the use of disease modifying therapies (DMT) is not fully understood. Objective To assess the observed versus expected number of cancers in MS patients, and family history of cancer, among DMT users and DMT naïve patients. Methods Cancer, DMT use, and family history of cancer were assessed using the New York State Multiple Sclerosis Consortium (NYSMSC) registry. Self-reported cancers in MS patients were tested for associations with DMT use, family history of cancer and other factors. Expected number of cancer cases was estimated using age- and gender-specific prevalence and incidence rates from the general population. Results The prevalence of cancer in males and females in the NYSMSC cohort was lower than expected (p < 0.001). Patients with cancer were older at MS diagnosis and more likely to be female (p < 0.001). MS patients with a personal history of cancer were more likely to report DMT use (p < 0.001) and family history of cancer (p < 0.001). Multivariable analysis did not support a higher risk of cancer after DMT initiation. Conclusions We report a lower than expected number of cancer cases in MS patients compared to the general population. MS patients with a personal history of cancer were more likely to report DMT use suggesting that DMTs may abrogate the lower incidence of cancer in MS.