Systemic Lupus Erythematosus and Mortality in Elderly Patients With Early Breast Cancer

Objective Patients with cancer and systemic lupus erythematosus (SLE) may have worse outcomes than those without SLE, given their comorbidities. We examined survival in elderly women with breast cancer (BC) and SLE and hypothesized that survival would be decreased compared with women with BC but without SLE. Methods We identified patients with BC and SLE and patients with BC without SLE in the Texas Cancer Registry and Surveillance, Epidemiology, and End Results, linked to Medicare claims. Overall survival (OS) was estimated after matching (age and cancer stage) and in multivariable Cox proportional hazards models adjusting for other cancer characteristics, treatment, and comorbidities. Two additional cohorts of women without cancer with and without SLE were also studied. Results We identified 494 BC SLE cases and 145,517 BC non‐SLE cases, of whom we matched 9,708. Women with SLE were less likely to receive radiation, breast conserving surgery, or endocrine therapy. The 8‐year OS estimate for women with early BC (stages 0–II) with and without SLE was 52% (95% confidence interval [95% CI] 45%–59%) and 74% (95% CI 73%–75%), respectively. In the Cox multivariable model, BC and SLE had increased risk of death (hazard ratio [HR] 1.65, 95% CI 1.38–1.98). Women with BC and SLE also had increased risk of death compared with women with SLE but without cancer (HR 1.42, 95% CI 1.05–1.92) after adjusting for SLE severity. Women with SLE and BC received less glucocorticoids, antimalarials, and immunosuppressants after cancer diagnosis than those without cancer. Conclusion Systemic lupus is a risk factor for increased mortality in women with early BC.