Objective: We conducted a retrospective cohort study to examine cancer risk in a large cohort of systemic lupus erythematosus (SLE) patients in California.
Methods: The cohort consisted of individuals with SLE derived from statewide patient discharge data during the period 1991-2002. SLE patients were followed using cancer registry data to examine patterns of cancer development. Standardized incidence ratios (SIRs) and 95% CI were calculated to compare the observed to expected numbers of cancers based on age-, race-, and sex-specific incidence rates in the California population.
Results: The 30,478 SLE patients were observed for 157,969 person-years. A total of 1,273 cancers occurred within the observation interval. Overall cancer risk was significantly elevated (SIR = 1.14, 95% CI = 1.07-1.20). SLE patients had higher risks of vagina/vulva (SIR = 3.27, 95% CI = 2.41-4.31) and liver cancers (SIR = 2.70, 95% CI = 1.54-4.24). Elevated risks of lung, kidney, and thyroid cancers and several hematopoietic malignancies were also observed. Individuals had significantly lower risks of several screenable cancers, including breast, cervix, and prostate.
Conclusions: These data suggest that risks of several cancer types are elevated among SLE patients. Detailed studies of endogenous and exogenous factors that drive these associations are needed.