Impact of breast cancer characteristics on the development and time to liver metastases: population-based study

Abstract Background Breast cancer (Bc) is the leading cause of cancer-related death in women. In many patients, BC liver metastases (BCLM) are associated with short survival. The aims of this study were to investigate the risk of and time to BCLM in each BC surrogate subtype, and to determine the incidence of BCLM in a population-based setting. Methods The Swedish national breast cancer registry identified patients with Bc in a regional cohort from 2009 to 2018. The cohort was followed until January 2023. Cox regression analysis was used to determine the risk of BCLM for each subtype. Kaplan–Meier estimates determined the probability of BCLM for each subtype over time. Results In all, 7292 patients with Bc were included in the study. Distant metastases developed in 755 patients (10.4%); of these, 345 (45.7%) developed BCLM. The BCLM incidence rate was 8 per 1000 person-years. Only 13 patients had oligometastases isolated to the liver. Triple-negative, non-luminal human epidermal growth factor receptor 2 (HER2)-positive and luminal B cancers had the highest risk of BCLM. T category, nodal status, and Nottingham histological grade III were also strongly associated with BCLM. The median time from Bc diagnosis to BCLM was 36 months. Patients with HER2-positive BC subtypes developed BCLM early, at a median of only 9 months. Conclusion Bc subtype is correlated to the risk and timing of BCLM development. BCLM are common in advanced Bc, but isolated oligometastases are rare.