Magnetic resonance imaging-guided radiotherapy for portal vein tumor thrombus in hepatocellular carcinoma: outcomes and prognostic factors.

Background: High-dose prescribed radiotherapy has been attempted to improve local control and restore portal vein in patients with hepatocellular carcinoma (HCC) complicated with portal vein tumor thrombus (PVTT). The aim of this study was to evaluate feasibility of real-time tumor-tracking magnetic resonance imaging-guided radiotherapy (rtMRgRT) for PVTT in HCC. In addition, prognostic factors for overall survival (OS) and progression pattern after radiotherapy (RT) were analyzed.

Methods: We retrospectively reviewed the data of 34 patients who had unresectable HCC complicated with PVTT and who were treated with rtMRgRT using hypofractionated radiotherapy (HFRT) and stereotactic body radiation therapy (SBRT) between June 2019 and October 2023. HFRT was performed with a total of 50-60 Gy in 10 fractions, and SBRT was performed in a range of 36-50 Gy in 4-5 fractions. The median biologic effective dose with an a/b ratio of 10 was 100 Gy₁₀ (range: 68.4-100 Gy₁₀).

Results: Twenty-one patients (61.7%) had an objective response (complete response and partial response) to PVTT; the 1-year estimated local control rate was 77.7%. The median progression-free survival and OS were 5.2 and 10.6 months, respectively. The predominant initial pattern of progressive disease after RT was outfield intrahepatic progression (21/29 cases, 72.4%). RT responder (hazard ratio [HR], 0.33; 95% confidence interval [CI], 0.12-0.88; p = 0.026) and combined transarterial chemoembolization (TACE) within 1-month post-RT (HR, 0.24; 95% CI, 0.08-0.73; p = 0.012) were favorable prognostic factors for OS.

Conclusions: The rtMRgRT demonstrated feasibility in treatment of PVTT with favorable overall response and local control. Response to RT and combined TACE within a month post-RT were favorable prognostic factors for OS. Given the predominant patterns of disease progression after RT, timely management of HCC outside RT field may be crucial for enhancing the survival of patients with PVTT undergoing RT. The early combination of TACE within a month post-RT may be beneficial in this regard. Further prospective studies are needed to determine the optimal sequencing and timing for combining RT and other local therapies in patients with PVTT.