Malignant neoplasms in autoimmune rheumatic diseases: examination of the risk of developing a malignancy among five different rheumatic diseases in one institution.

Relationships between autoimmune rheumatic diseases and malignant neoplasms have been discussed, but there is no study of the different rheumatic diseases examining the risk of developing cancer. Our study has examined probabilities for developing malignancy among patients with connective tissue diseases seen in a single institution. Patients with autoimmune rheumatic disease and malignancy were compared with patients with the same autoimmune rheumatic diseases without malignancy. All cases identified through record-linkage from 1964 to 1996 were selected. Four controls per case were randomly selected from a pool of 3228 patients. The rheumatic diseases considered were rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), primary Sjögren's syndrome (pSS), dermatomyositis-polymyositis (DM-PM), and systemic sclerosis (Scl). The statistical analysis was conducted by conditional logistic regression, testing rheumatic disease as main effect. We identified 72 cases and 288 controls. Fifty-three of the cases had solid tumors, and 19 had lymphoproliferative neoplasms. The risk of developing a malignancy was considerably higher in DM-PM than in SLE (odds ratio [OR] = 17.5, 95% confidence interval [CI] 4.1-75.7), in pSS than in SLE (OR = 5.7, 95% CI 2.2-15.1), and in Scl than in SLE (OR = 5.4, 95% CI 1.6-18.0). These risks persisted after controlling for rheumatic disease duration, the time the disease was active, and anti-rheumatic treatment. RA had an OR of 1.8 (95% CI 0.9-3.4) with respect to SLE. This is the first study which describes the magnitude of risks among rheumatic diseases associated with the probability of developing a malignant neoplasm whether lymphoproliferative or solid. The risks in this series depend on the primary rheumatic disease, with DM-PM, pSS, and Scl all having greater risk than SLE.