Abstract

The incidence of malignant neoplasms among 11 483 male and 34 618 female individuals with rheumatoid arthritis was studied using two separate nationwide data registers covering the whole Finnish population: the Social Insurance Institution's Population Data Register, which includes information on medication for certain chronic diseases, and the Finnish Cancer Registry, with data on all cancer patients diagnosed in Finland. The follow-up comprised a total of 213 911 person years. The total incidence of all malignant neoplasms was higher in males and on the level expected in females. The expected number of cases of leukemia, lymphomas, Hodgkin's disease and myeloma in both sexes was 59·6 as compared with the 130 cases observed. This difference is statistically highly significant (p<0·001). The incidence of cancer of the respiratory organs was higher in males, and the incidence of cancer of the rectum and stomach lower than expected in rheumatoid females.