Underlying nonalcoholic fatty liver disease is a significant factor for breast cancer recurrence after curative surgery.

Breast cancer is the most common cancer among women worldwide, and it is a main cause of death in women. As with breast cancer, metabolic components are important risk factors for the development of nonalcoholic fatty liver disease (NAFLD). In this retrospective cohort study, we aimed to determine the prevalence of NAFLD in patients with breast cancer and the impact of NAFLD on the prognosis of breast cancer. Patients with breast cancer were enrolled in the study from January 2007 to June 2017. Hepatic steatosis was evaluated through non-enhanced computed tomography scan by measuring Hounsfield Units in the liver and spleen, respectively; 123 healthy controls who underwent non-enhanced computed tomography scan were also analyzed. The prevalence of NAFLD in patients with breast cancer was 15.8% (251/1587), which was significantly higher than in healthy controls (8.9%, 11/123) (P=.036). Overall survival did not significantly differ between the groups with and without NAFLD (P=.304). However, recurrence-free survival was significantly higher in patients without NAFLD than in those with NAFLD (P=.009). Among breast cancer patients receiving endocrine treatment, the NAFLD group showed a higher cumulative incidence of significant liver injury than the group without NAFLD (P<.001). The prevalence of NAFLD in patients with breast cancer is significantly higher than in healthy controls. Moreover, breast cancer patients with NAFLD showed poorer prognosis in terms of recurrence. Therefore, diagnostic evaluation for NALFD is important in managing patients with breast cancer.