Objective
Patients with autoimmune disease may have impaired cancer survival. The aim was to investigate the association between autoimmune disease and ovarian cancer survival.

Methods
From the Extreme study, we included women diagnosed with epithelial ovarian cancer (EOC) in Denmark during 1990–2014 (n = 11,870). Information on exposure and covariates was retrieved from nationwide registries. Using pseudo-values, we estimated absolute and relative 5- and 10-year survival probabilities with 95% confidence intervals (CIs) for autoimmune diseases combined and for the four most common individual disorders in our study population, namely type 1 diabetes, rheumatoid arthritis, Graves' disease, and inflammatory bowel disease.

Results
The overall 5- and 10-year absolute survival probabilities were 35% and 24%, respectively, in women with EOC without autoimmune disease. Autoimmune diseases combined was not significantly associated with survival among women with EOC (5-year adjusted relative survival probability = 1.01, 95% CI: 0.94–1.09; 10-year adjusted relative survival probability = 0.90, 95% CI: 0.81–1.00). However, stratification by disease stage showed an impaired 10-year survival in women with autoimmune disease and a localized EOC (relative survival probability = 0.86, 95% CI: 0.76–0.97). None of the individual autoimmune diseases were statistically significantly associated with EOC survival.

Conclusions
Only among women with localized EOC, there seemed to be a long-term survival loss associated with a history of autoimmune disease. In contrast, no significant association between a history of autoimmune disease and survival was observed in women with nonlocalized EOC where the survival is already low.