Background/Purpose: Women with systemic lupus erythematosus (SLE) who develop breast cancer (BC), may receive different therapies (e.g. radiation) than women with BC who do not have SLE. They also have more comorbidities that may affect survival. Our objective was to evaluate survival in women with both SLE and BC, compared with women with BC alone or SLE without cancer.

Methods: We conducted a retrospective observational study using the Surveillance, Epidemiology, and End Results (SEER) and the Texas Cancer Registry (TCR) dataset linked to Medicare claims. We included women aged ≥66 years diagnosed with BC from 2005-2015, and a 5% Medicare non-cancer random sample who resided in the SEER/TCR region. Based on BC and SLE status, we included three groups: 1) BC SLE, 2) BC non-SLE, 3) non-cancer SLE. For women with BC, we collected cancer characteristics (age and year at diagnosis, stage, hormone receptor status) and treatment (chemotherapy, radiation therapy, and surgery type). We matched BC SLE and BC non-SLE with cancer characteristics. We matched non-cancer SLE women with BC SLE with birth year and race and used the matched date of diagnosis as the index date for non-cancer women. SLE was defined with ≥2 international classification of diseases (ICD) 9 or 10 diagnosis codes within 1 year before BC diagnosis (or index date). Overall survival (OS) and breast cancer specific survival (BCSS, only for BC women) were measured from date of diagnosis (or index date). Kaplan-Meier methods and multivariable Cox proportional hazards models were implemented to evaluate the association of survival outcomes with groups adjusting for cancer characteristics and treatment (for BC), comorbidities and the Garris index of SLE disease severity (for SLE only).

Results: We identified 494 BC SLE cases, 145,517 BC non-SLE, and matched 268 non-cancer SLE. The 5-year overall survival for women with early breast cancer (stages 0-II) with and without SLE was 74% (95% confidence interval [CI] 68%-78%) and 86% (95% CI 85%-86%) (p < 0.001) respectively. In multivariable models adjusting for cancer characteristics, treatment and comorbidities, BC SLE had increased risks of death (HR 1.65; 95% CI 1.38 to 1.98) compared to the BC non-SLE group but no significant association with BCSS. Comparisons between the SLE groups showed that BC SLE had increased risks of death compared non-cancer SLE after adjusting for SLE disease severity (HR 1.42; 95% CI 1.05 to 1.92).

Conclusion: Our data shows that patients with BC and SLE are at risk of earlier mortality compared to patients with BC alone, even after adjusting for SLE disease activity and comorbidities. Further research is needed to investigate the determinants of these findings and improve survival in this population.

« Back to ACR Convergence 2021

ACR Meeting Abstracts - https://acrabstracts.org/abstract/systemic-lupus-erythematosus-is-a-risk-factor-for-mortality-in-older-patients-with-early-stage-breast-cancer/