Marrie RA, Maxwell C, Mahar A, et al. - Researchers used population-based data sources to compare incidence rates and cancer-specific mortality rates in MS and matched cohorts to assess if cancer risk varies in people with and without multiple sclerosis (MS). Using population-based administrative data from Manitoba and Ontario, Canada, a retrospective matched cohort study was performed. Fifty-three thousand nine hundred eighty-three MS cases and 269,915 controls were included. There is no difference in the incidence or mortality rates of breast and colorectal cancers among people with and without MS, but the incidence and mortality rates of bladder cancer has increased. Regarding prostate, uterine, and CNS cancers, the incidence differed between the MS and matched cohorts, but mortality rates did not. In the MS population, reported differences in the occurrence of certain cancers may indicate differences in ascertainment rather than true differences.