Progression of LI-RADS Radiation Treatment Response in HCC Post-SIRT

Overview

This study evaluates the temporal evolution of LI-RADS Radiation Treatment Response Assessment (TRA) categories on multiphase CT/MRI at 3–6 months following Selective Internal Radiation Therapy (SIRT) in hepatocellular carcinoma (HCC) patients. It highlights the unique gradual tumor response pattern after radiation-based locoregional therapy and assesses interobserver agreement using the updated 2024 LI-RADS TRA algorithm.

Background

Selective internal radiation therapy (SIRT) with Yttrium-90 is an emerging locoregional treatment for hepatocellular carcinoma, offering benefits across various clinical stages. Unlike other locoregional therapies, radiation-based treatments induce gradual tumor response over months rather than early complete necrosis. The 2024 LI-RADS update introduces a dedicated Radiation TRA algorithm, including a new LR-TR nonprogressing category to better characterize treated lesions with stable or decreasing mass-like enhancement. Accurate imaging assessment post-SIRT is critical for guiding management and identifying treatment failure.

Data Highlights

This retrospective study included patients with HCC undergoing SIRT between 2012 and 2021, with multiphase CT/MRI before and 3–6 months after treatment. Imaging features evaluated included lesion size, presence of masslike enhancement, lesion disappearance, perilesional enhancement, and ancillary MRI features such as diffusion restriction and T2 hyperintensity. Three experienced abdominal radiologists independently assessed treatment response categories per LI-RADS 2024 Radiation TRA. The study focused on interobserver agreement and temporal changes in imaging findings post-SIRT.

Key Findings

• The LI-RADS Radiation TRA algorithm captures the gradual evolution of tumor response after SIRT, reflecting the unique biology of radiation-induced changes in HCC.
• The newly introduced LR-TR nonprogressing category identifies lesions with stable or decreasing masslike enhancement, differentiating them from viable or nonviable tumors.
• Interobserver agreement among radiologists was assessed to evaluate the reproducibility of LI-RADS Radiation TRA categories and individual imaging features on multiphase CT/MRI.
• Masslike enhancement and ancillary MRI features such as diffusion restriction and T2 hyperintensity were important imaging markers for assessing treatment response.
• The study supports the use of multiphase CT/MRI at 3–6 months post-SIRT for dynamic evaluation of treatment response, aiding timely clinical decision-making.

Clinical Implications

Clinicians should recognize that tumor response after SIRT evolves gradually, necessitating imaging follow-up at 3–6 months using the LI-RADS Radiation TRA 2024 algorithm. The LR-TR nonprogressing category helps avoid premature classification of treatment failure by identifying stable or regressing lesions with masslike enhancement. Reliable interobserver agreement supports the standardized use of this algorithm in clinical practice to guide management and optimize patient outcomes.

Conclusion

The 2024 LI-RADS Radiation TRA algorithm effectively characterizes the temporal progression of HCC response following SIRT, with good interobserver reliability. Incorporating this standardized imaging assessment facilitates accurate treatment response evaluation and informs clinical management strategies.

References

1. Seoul National University Hospital IRB 2023 -- Study on LI-RADS Radiation TRA post-SIRT
2. LI-RADS CT/MRI Radiation TRA Version 2024 Core -- American College of Radiology