Increased Risk of Malignancy in Patients with Systemic Lupus Erythematosus

BACKGROUND: Systemic lupus erythematosus is a chronic, multisystem, autoimmune disorder that primarily affects women. Morbidity and mortality have improved for lupus patients during the last 15 years. An increased risk of malignancy in patients with lupus has been shown in some, but not all studies. The purpose of this study was to ascertain cancer risk in lupus patients by linking two disease registries. METHODS: Participants in the Chicago Lupus Cohort included 616 women with lupus who were residents of Cook County, Illinois. They were seen during 1985-1995 at 4 University, inner city, and suburban inpatient and outpatient clinics in Chicago. Malignancies occurring in these subjects during the study interval, 1985-1995, were identified from the Illinois State Cancer Registry by matching name, birthdate, and social security number. Standardized incidence ratios (SIRs) were estimated for all malignancies in this cohort of lupus patients using age, gender, and all race or race-stratified specific cancer incidence data from Cook County, Illinois. RESULTS: The registry linkage study with the Illinois State Cancer Registry documented that 30 women with lupus had a malignancy. The expected number of malignancies for women in the lupus cohort was 15.0. There were 8 cases of breast cancer and 4 each of lung and cervical cancer. In the remaining 14 women, 12 different types of cancers were noted. The SIR and 95% confidence interval (CI) for malignancy for all women with lupus in the study were 2.0 (1.4, 2.9) and lung cancer was the only individual cancer increased in all women--SIR and 95% CI were 3.1 (1.3, 7.9). In the analysis stratified by race, the risk of malignancy (SIR and 95% CI) was increased in Caucasian women, 2.3 (1.4, 3.9). Breast cancer was the only individual cancer increased in Caucasian women with lupus with an SIR and 95% CI of 2.9 (1.4, 6.4). CONCLUSIONS: Lupus patients have an increased risk of malignancy. Breast, lung, and gynecological malignancies were the most common malignancies observed in the cohort and breast cancer was significantly increased in Caucasian women.