Breast, Ovarian and Endometrial Cancers in Women Diagnosed with SLE before Age 40

Abstract

Objectives: Various studies have confirmed an overall increase in cancers in systemic lupus, SLE. This increased incidence is largely driven by haematological malignancies, while for some cancers there may be a decreased incidence in SLE (breast, endometrial and ovary). Although 90% of SLE patients are female, only a few studies in the past have focussed on breast, endometrial, and ovarian cancer. To date, no study so far has looked at the incidence of these female reproductive cancers specifically in young females diagnosed with SLE, despite the fact that SLE is mostly diagnosed in female patients in child bearing years. Our objective was to determine the incidence of breast, ovarian and endometrial cancer in females diagnosed with SLE prior to age 40. Methods: Data were obtained from a multicentre cohort study of SLE patients from 23 centres. The SLE diagnosis was tablished by American College of Rheumatology Criteria or clinical criteria. Patients were followed up in outpatient clinics and cancer cases were ascertained through linkage with regional tumor registries. Standardized incidence ratios (SIR) were calculated for breast, ovarian and endometrial cancer by dividing the observed number events for a given cancer by the expected number of the respective cancer. Expected numbers of cancers were determined by multiplying the person years at risk in the cohort by age and sex matched general population cancer rates. Results: 5,406 females diagnosed with SLE under age 40 (mean age at diagnosis 26.8 years, standard deviation, SD, 7.4) were observed for a total of 44,073 patient-years (average follow up 8 years). A total of 121 cancers were diagnosed in this population during the observation period, 1/4 of these cancers accounted for breast (29), ovarian (1) and endometrial cancer (3).Data suggested a decrease in breast (SIR 0.38, 95% confidence interval, CI 0.26-0.55) and endometrial cancer (SIR 0.33, 95% CI 0.07-0.96). There was a trend towards a decrease in ovarian cancer (SIR 0.25, 95% CI 0.01-1.41) in female patients who were diagnosed with SLE under age 40. Conclusion: In the present cohort study, data suggested a decreased risk of breast and endometrial cancer in females who developed SLE prior to age 40. The data on ovarian cancer incidence are inconclusive. Limitations of the current analyses include that the general population cancer rates were not perfectly matched for geography, race/ethnicity and calendar year of cancer diagnosis.