To investigate the clinical characteristics of breast cancer patients with liver metastasis and the risk factors on prognosis.

The clinical data of 3 468 de novo stage Ⅳ breast cancer patients with organ metastasis in the Surveillance, Epidemiology, and End Results (SEER) database of National Cancer Institute of the USA from 2010 to 2013 were analyzed. Patients were divided into liver metastasis group (n=1 001) and non-liver metastasis group (n=2 467). χ² test and binary Logistic regression were used to compare the clinical characteristics between two groups. There were 930 liver metastasis patients with complete follow-up data for sub-analysis. The Kaplan-Meier method was used to calculate the OS in patients with liver metastasis, and the effect of various factors on the survival rate was analyzed by Log-rank method. The significant factors in univariate analysis were included in the multivariate Cox regression model to screen out the independent risk factors.

The following clinical characteristics presented a significant difference between liver metastasis group and non-liver metastasis group: age at diagnosis, race, histological grade, pathological type, primary side, ER, PR and HER-2 expression (χ²=25.543, 8.516, 55.474, 18.182, 4.851, 96.440, 105.707, 148.941; all P<0.050). Binary Logistic regression results showed that age at diagnosis (OR=0.718, 95%CI: 0.605-0.851, P<0.001), histological grade(OR=1.156, 95%CI: 1.007-1.326, P=0.039), ER (OR=0.712, 95%CI: 0.574-0.885, P=0.002), PR (OR=0.681, 95%CI: 0.557-0.834, P<0.001) and HER-2 (OR=2.167, 95%CI: 1.835-2.558, P<0.001) were independent factors affecting liver metastasis. In 930 patients, the median survival was 23 months, the 1-year OS was 64.9% and 3-year OS was 34.2%. The survival analysis showed that age at diagnosis(χ² =53.968, P<0.001), race(χ² =9.677, P=0.008), histological grade (χ²=6.826, P=0.033), T stage (χ²=10.467, P=0.016), N stage(χ² =18.057, P<0.001), surgery at primary lesions (χ² =19.719, P<0.001), radiotherapy at primary lesions (χ²=11.873, P=0.003), metastasis of other organs (χ²=12.262, P<0.001), ER (χ²=28.045, P<0.001), PR (χ²=40.418, P<0.001) and HER-2 expression (χ²=23.844, P<0.001) were significantly correlated with the patients’ survival. Cox regression analysis showed that age at diagnosis (HR=1.544, 95%CI: 1.353-1.762, P<0.001), histological grade (HR=1.249, 95%CI: 1.038-1.503, P=0.018), T stage (HR=1.103, 95%CI: 1.004-1.211, P=0.042), surgery at primary lesions (HR=0.565, 95%CI: 0.457-0.700, P<0.001), ER (HR=0.749, 95%CI: 0.586-0.958, P=0.022), PR (HR=0.586, 95%CI: 0.453-0.759, P<0.001) and HER-2 (HR=0.517, 95%CI: 0.418-0.640, P<0.001) were independent prognostic factors in breast cancer patients with liver metastasis.

The risk of liver metastasis in breast cancer may be correlated with malignancy of the tumor. The prognosis of breast cancer patients with liver metastasis is poor. The patients with younger age at diagnosis, lower histological grade and T stage, ER positive, PR positive and HER-2 positive have a better long-term prognosis. Surgical treatment for primary tumor can significantly improve the patients’ prognosis.