Clinical Results of Radiotherapy That Targeted for Tumor Thrombi from Hepatocellular Carcinoma: A Multicenter Retrospective Study

Background: The aim of this multicenter study was to evaluate the outcome of radiotherapy (RT) that targeted for tumor thrombi (TT) from hepatocellular carcinoma (HCC), including the portal vein, hepatic vein, inferior vena cava, and bile duct TT. Methods: Patients who received RT for the treatment of TT between 2005 and 2020 were retrospectively reviewed. We compared patient characteristics, overall survival (OS), the combined chemotherapy regimen, and objective response rates (ORRs) between the treatment modalities and analyzed cumulative incidence formula (CIF) for the deterioration in the Child-Pugh class and the progression of intrahepatic tumors. Results: We evaluated 64 patients, 39 of whom received combined chemotherapy with RT. Multivariate analysis showed that the Child-Pugh class, primary tumor size and the response of TT were significant prognostic factors for OS and the total equivalent dose in 2 Gy fractions (EQD2) of more than 48.75 Gy significantly contributed to ORRs (p=0.04). In the multivariate analysis of CIF, only acute liver damage was the significant factor for the deterioration in the Child-Pugh class (p=0.01) and the length of TT was significant for the progression of intrahepatic tumors (p=0.03). Conclusion: High doses should be delivered to TT, but long tumor thrombi are difficult to control. Tumor thrombus length is more important in predicting intrahepatic progression than the location of the tumor thrombus.