The risk of cancer in rheumatoid patients in Japan.

In order to clarify the risk of cancer development in patients with rheumatoid arthritis (RA), the incidence of malignant tumors during a follow-up period was investigated in RA patients at the Center for Adult Diseases, Osaka, Japan. Six hundred and fifty-five eligible rheumatoid patients (131 males, 524 females) who were admitted to our institute between 1980 and 1989 were matched against the files of the Osaka Cancer Registry. Among them, a total of 26 patients (5 males, 21 females) were noted to have developed some kinds of cancer. The female RA patients demonstrated a significantly higher incidence of all cancers than the general population, with an observed/expected (O/E) ratio of 1.71 (95% confidence interval = 1.06-2.62). Cancer of the buccal cavity/pharynx and thyroid cancer also showed a higher incidence in female RA patients, with O/E ratios of 12.93 and 2.74, respectively.