Pattern of distant extrahepatic metastases in primary liver cancer: a SEER based study

Background and Aims: Primary liver cancer remains still the common cause of cancer-related deaths globally and the prognosis for patients with extrahepatic metastasis is poor. The aim of our study was to assess extrahepatic metastatic pattern of different histological subtypes and evaluate prognostic effects of extrahepatic metastasis in patients with advanced disease. Methods: Based on the Surveillance, Epidemiology and End Results (SEER) database, eligible patients diagnosed with primary liver cancer was identified between 2010 to 2012. We adopted Chi-square test to compared metastasis distribution among different histological types. We compared survival difference of patients with different extrahepatic metastasises by Kaplan-Meier analysis. Cox proportional hazard models were performed to identify other prognostic factors of overall survival. Results: We finally identified 8677 patients who were diagnosed with primary liver cancer from 2010 to 2012 and 1775 patients were in distant metastasis stages. Intrahepatic cholangiocarcinoma was more invasive and had a higher percentage of metastasis compared with hepatocellular carcinoma. Lung was the most common metastasis and brain was the least common site for both hepatocellular carcinoma and intrahepatic cholangiocarcinoma. Extrahepatic metastasis could consider as an independent prognostic factor for patients with liver cancer. Patients with brain metastasis had the worst prognosis, compared with other metastasis in overall survival (OS) and cancer-specific survival (CSS) analysis. Conclusions: Different histological subtypes of liver cancer had different metastasis patterns. There were profound differences in risk of mortality among distant extrahepatic metastatic sites. Results from our studies would provide some information for follow-up strategies and future studies.