Incidence and risk of cancer among multiple sclerosis patients: A matched population-based cohort study

Background and purpose Studies have not yet found conclusive results on the risk of cancer in patients with multiple sclerosis (MS). This study aimed to compare the incidence of all cancers and of specific types of cancer between MS patients and the general population by age and by sex. Methods All prevalent MS patients identified between 2008 and 2014 in the nationwide French health care database (Systeme National des Donnees de Sante) and without history of malignancy were included in a cohort study and followed up until cancer occurrence, date of death, or 31 December 2015, whichever came first. MS patients were matched based on sex and year of birth to non-MS controls from the general population without cancer before index date. Incidence rate was reported per 100,000 person-years (PY), and risk of cancer was estimated by type of cancer, age, and sex using a Cox model (hazard ratio [HR] and its 95% confidence interval [CI]). Results Overall, 576 cancers per 100,000 PY were observed in MS patients versus 424 per 100,000 PY in the control population. The risk of cancer was higher among MS patients than among population controls whether considered overall (HR = 1.36, 95% CI = 1.29-1.43) or for prostate (HR = 2.08, 95% CI = 1.68-2.58), colorectal and anal (HR = 1.35, 95% CI = 1.16-1.58), trachea, bronchus, and lung (HR = 2.36, 95% CI = 1.96-2.84), and to a lesser extent, breast cancer (HR = 1.12, 95% CI = 1.03-1.23). Conclusions MS patients were associated with increased risk of cancer compared to population controls.