Prognostic difference of single metastasis in different sites of hepatocellular carcinoma: a population-based study.

Background: There is a notable difference in prognosis between single and multiple metastases from hepatocellular carcinoma (HCC). We aimed to identify the prognostic differences among HCC patients with single metastasis to different sites. Methods: The study focused on patients with single metastasis to different organs from HCC from the Surveillance, Epidemiology, and End Results database between 2010 and 2015. We used the Kaplan-Meier method to determine overall survival (OS) and disease-specific survival (DSS). Univariate and multivariate Cox regression analysis, as well as floating absolute risk (FAR), were introduced to compare prognostic differences among the single metastasis. We applied the conditional survival (CS) to calculate the time-varying survival probability. Results: The study included 2,197 individuals. In multivariate Cox analysis, single lung metastasis [hazard ratio (HR) =1.293, 95% confidence interval (CI): 1.053-1.587, P=0.01] was linked to worse OS than single intrahepatic metastasis, while single lung metastasis (HR =1.395, 95% CI: 1.103-1.764, P=0.005) and single bone metastasis (HR =1.306, 95% CI: 1.021-1.67, P=0.03) possessed shorter DSS than single liver metastasis. FAR revealed that OS and DSS for single pulmonary metastasis were inferior to those of bone metastasis. In the subgroup analysis, chemotherapy played an interactive role in the comparison of DSS in single bone metastasis vs. liver metastasis group, as well as single lung metastasis vs. liver metastasis group, suggesting that chemotherapy may improve the survival. CS analyses showed a marked improvement in patients with single metastasis over time. Conclusions: The prognosis of single pulmonary metastasis was worse than that of single bone metastasis and single intrahepatic metastasis. The prognosis of single brain metastasis could not be determined temporarily due to data limitations.