To estimate the incidence and analyze any cancer-associated factors in patients with systemic lupus erythematosus (SLE), differentiating between hormone-sensitive (HS) and non-HS cancers.
This was a retrospective multicenter study of a patient cohort from the Systemic Lupus Erythematosus Registry of the Spanish Society of Rheumatology. Included were the first cancer post-SLE diagnosis, clinical and sociodemographic information, cumulative damage, severity, comorbidities, treatments, and refractoriness. Cancers were classified as HS (prostate, breast, endometrium, and ovarian) and non-HS (the remainder). The standardized incidence ratio (SIR) was calculated and logistic regression models were built.
A total of 3,539 patients (90.4% women) were included, 154 of whom had cancer (91% female), and 44 had HS cancer (100% female). The cancer SIR was 1.37 (95% confidence interval [95% CI] 1.15-1.59), with higher values in women age <65 years (SIR 2.38 [95% CI 1.84-2.91]). The SIR in women with HS versus non-HS cancer was 1.02 (95% CI 0.13-1.91) and 1.93 (95% CI 0.98-2.89). In HS versus non-HS cancers, SLE diagnostic age (odds ratio [OR] 1.04 [P = 0.002] versus 1.04 [P = 0.019]), and period of disease evolution (OR 1.01 [P < 0.001] versus 1.00 [P = 0.029]) were associated with cancer. The Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (OR 1.27 [P = 0.022]) and angiotensin-converting enzyme (ACE) inhibitor prescriptions (OR 2.87 [P = 0.048]) were associated with non-HS cancers.
Cancer incidence in patients with SLE was higher than in the Spanish population, particularly among young women. This increase might be due to non-HS cancers, which would be associated with SLE involving greater cumulative damage where more ACE inhibitors are prescribed.