Cancer incidence following hospitalization for multiple sclerosis in Denmark.

Incidence of various cancers was evaluated in a cohort of 5359 multiple sclerosis (MS) patients, identified through hospital discharge records between 1977 and 1987 and followed for an average of 5.2 years. Computerized linkage with the Danish Cancer Registry uncovered 210 cancer cases which was significantly more than expected based on national rates (relative risk (RR) = 1.29). Over half of the excess, however, was observed for non-melanoma skin cancer and tumors of the urinary tract, which may be related to increased medical surveillance among MS patients compared to the Danish population as a whole. There was a significant excess of nasopharyngeal carcinomas in the cohort (RR = 17.3), but based on only 3 cases and seen only among women. Hematologic and lymphatic malignancies were not increased, adding little support to previous suggestions of a possible association of these malignancies with MS. An excess of brain tumors, seen only in women, may represent situations where the tumor caused symptoms which were interpreted as MS. Overall, the data suggest that a patient with MS is not at unusual risk for subsequent cancer development, but the relatively short follow-up of the population is a limitation of the investigation.