Pretreatment platelet count early predicts extrahepatic metastasis of human hepatoma

Background & Aims: Thrombocytosis is associated with metastasis in many human cancers. Most hepatocellular carcinomas (HCC) develop in cirrhotic livers, which are characterized by thrombocytopenia. We aimed to elucidate the pretreatment platelet count in prediction of extrahepatic metastasis of HCC during the follow-up. Methods: Three cohorts containing 1660, 480 and 965 HCC patients enrolled from three hospitals were used for discovery and validation respectively. Pretreatment clinical factors associated with extrahepatic metastasis during follow-up up to 5 years were identified using multivariate Cox regression model. Results: In early-stage HCC (BCLC stage 0-A), pretreatment platelet count (hazard ratio [HR], 1.04 per 10,000/μl; 95% CI, 1.01-1.07; P = 0.010) and serum alpha-foetoprotein (AFP) >100 ng/ml (HR, 1.70; 95% CI, 1.04-2.78; P = 0.033) were the only two independent factors associated with extrahepatic metastasis. Receiver operating characteristic evidenced that pretreatment platelet count predicted metastasis better than AFP did. Survival tree analysis identified platelet counts <118,000/μl (HR, 0.49; 95% CI, 0.38-0.63; P < 0.001) or >212,000/μl (HR, 2.12; 95% CI, 1.67-2.70; P < 0.001) to categorize patients into low and high risk of metastasis subgroups, which were verified using both validation cohorts. Conclusions: Pretreatment platelet count is a reliable marker to predict extrahepatic metastasis of early-stage HCC following curative treatment. Cirrhotic thrombocytopenia contributes to relatively low metastasis incidence of HCC than many other cancers. High platelet count identifies a subgroup of HCC patients at high risk of metastasis, who might benefit from adjuvant therapies following initial curative treatment.