Systemic lupus erythematosus and the risk of malignancy

The objective of this study was to determine the relative risks of malignan cy and of site-specific malignancies in patients with systemic lupus erythe matosus (SLE). A cohort of 297 patients (91% Caucasian) with SLE were seen between 1975 an d 1994 and followed for a mean of 12 years at the University of Saskatchewa n Rheumatic Disease Unit. Expected cancer incidence rates were determined b ased on Province of Saskatchewan population statistics matched to each stud y patient for age, sex and calendar year of follow-up. Standardized inciden ce ratios (SIRs) of observed to expected cancers and 95% confidence interva ls (95% CI) were calculated. A total of 27 cases of cancer were observed, whereas only 16.9 were expecte d (SIR 1.59 (95% Ct 1.05-2.32)). For site-specific malignancies, an excess of cancer of the cervix (SIR 8.15 (95% CI 1.63-23.81)) as well as hemopoiet ic malignancy (SIR 4.9 (959/0 CI 1.57-11.43)) was found. The hemopoietic ca ncers were predominantly non-Hodgkin's lymphoma (SIR 7.01 (95% CI 1.88-17.9 6)). We did not find an association of malignancy with known risk factors, including use of cytotoxic agents. Increased risk of malignancy, notably non-Hodgkin's lymphoma and perhaps ce rvical cancer, should be regarded as a complication of SLE.