Background & Aims: This nationwide, multicenter study investigated treatment outcomes as well as the optimal radiotherapeutic strategy in patients with hepatocellular carcinoma (HCC) and portal vein tumour thrombosis (PVTT). Methods: We retrospectively reviewed the records of 985 patients who received radiotherapy (RT) for PVTT. The median equivalent RT dose was 48.75 Gy. Combined treatment, defined as liver-directed treatments performed within a month of RT, was administered to 657 patients (66.7%). The PVTT and primary tumour were irradiated in 413 patients (41.9%), and PVTT only was targeted in 572 patients (58.1%). Results: The response rate of the PVTT was 51.8%, and RT responders had a significantly longer survival than non-responders (15.2 vs. 6.9 months). Equivalent RT dose and combined treatment predicted response of PVTT. The median overall survival (OS) was 10.2 months. Multivariate analysis revealed the equivalent RT dose ˃45 Gy and combined treatment as significant positive factors for OS. In the propensity score matching analysis, the combined treatment group had better OS than the no combined treatment group, whereas the OS of the PVTT + primary tumour group did not differ significantly from that of the PVTT only group. Conclusion: The equivalent RT dose ˃45 Gy, given in combination with other treatments, provided better PVTT control and OS. The optimal RT volume is suggested for either PVTT + primary or PVTT only. Taken together, multimodal treatment with equivalent RT dose higher than 45 Gy is recommended for patients with HCC and PVTT.
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