Survival in patients with breast cancer and history of autoimmune disease.

1020 Background: Patients with autoimmune disease, specifically systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and Sjogren syndrome, are at reduced risk of developing breast cancer compared to those without a prior history of autoimmune disease. Despite this, little is known about the survival of patients with concurrent autoimmune disease and breast cancer. This study compared outcomes in patients with breast cancer with and without autoimmune disease. Methods: This study was a retrospective analysis of patients from SEER-Medicare databases from 2007-2014 with breast cancer. Patients with a history of autoimmune disease were identified using ICD-9 codes. The effects of autoimmune disease on overall survival (OS) and cancer-specific survival (CSS) were estimated using multivariable Cox regression and Gray’s method respectively controlling the effects of age, race and chronic kidney disease (CKD). The cumulative CSS was estimated taking death as a competing risk. Results: The overall prevalence of investigated autoimmune diseases among the 137,324 patients with breast cancer was 26.69%. The most common autoimmune diseases identified were RA (23.35%), psoriasis (2.41%) and SLE (1.12%). In stage IV breast cancer patients the OS and CSS were significantly higher in patients with autoimmune disease (p values < 0.0001), with a median OS of 36 months compared to 30 months in patients without autoimmune disease. After adjusting for the effects of age, race, and CKD, autoimmune disease was still predictive of higher OS (HR: 1.46, 95% CI: 1.37 – 1.57, p < 0.0001) and CSS (HR: 1.39, 95% CI: 1.29 – 1.5, p < 0.0001). Patients with autoimmune disease and stage I-III breast cancer, had lower OS (p < 0.0001, p < 0.0001, and p = 0.026 respectively) compared to patients without autoimmune disease. Conclusions: We found a higher prevalence of RA, Crohn disease, ulcerative colitis, and SLE in patients with breast cancer compared to cohorts of similar age ranges in the general population. History of autoimmune disease resulted in significantly improved OS and CSS in patients with stage IV breast cancer even when controlling for age, race and CKD, in this pre-immunotherapy cohort. These results suggest that that anti-tumor immunity plays an important role in late-stage breast cancer, and could be potentially exploited to improve the effectiveness of immunotherapy. Further research into the relationship between autoimmunity and breast cancer is warranted.