Stereotactic body radiation therapy (SBRT) following Yttrium-90 (⁹⁰Y) selective internal radiation therapy (SIRT): a feasibility planning study using ⁹⁰Y delivered dose

Abstract

Objective: 90Y selective internal radiation therapy (SIRT) treatment of hepatocellular carcinoma (HCC) can potentially underdose lesions, as identified on post-therapy PET/CT imaging. This study introduces a methodology and explores the feasibility for selectively treating SIRT-underdosed HCC lesions, or lesion subvolumes, with stereotactic body radiation therapy (SBRT) following post-SIRT dosimetry. Approach: We retrospectively analyzed post-treatment PET/CT images of 20 HCC patients after 90Y SIRT. Predicted tumor response from SIRT was quantified based on personalized post-therapy dosimetry and corresponding response models. Predicted non-responding tumor regions were then targeted with a hypothetical SBRT boost plan using a framework for selecting eligible tumors and tumor subregions. SBRT boost plans were compared to SBRT plans targeting all tumors irrespective of SIRT dose with the same prescription and organ-at-risk (OAR) objectives. The potential benefit of SIRT followed by a SBRT was evaluated based on OAR dose and predicted toxicity compared to the independent SBRT treatment. Main results: Following SIRT, 14/20 patients had at least one predicted non-responding tumor considered eligible for a SBRT boost. When comparing SBRT plans, 10/14 (71%) SBRTboost and 12/20 (60%) SBRTalone plans were within OAR dose constraints. For three patients, SBRTboost plans were within OAR constraints while SBRTalone plans were not. Across the 14 eligible patients, SBRTboost plans had significantly less dose to the healthy liver (decrease in mean dose was on average ± standard deviation, 2.09 Gy ± 1.99 Gy, ) and reduced the overall targeted PTV volume (39% ± 21%) compared with SBRTalone. Significance: A clinical methodology for treating HCC using a synergized SIRT and SBRT approach is presented, demonstrating that it could reduce normal tissue toxicity risk in a majority of our retrospectively evaluated cases. Selectively targeting SIRT underdosed HCC lesions, or lesion subvolumes, with SBRT could improve tumor control and patient outcomes post-SIRT and allow SIRT to function as a target debulking tool for cases when SBRT is not independently feasible.

Immunotherapy and Radiation Therapy Combinatorial Approaches in Hepatocellular Carcinoma

“…Similarly, SIRT, or radioembolization, which combines the embolic effect with targeted radiation delivery by directly injecting radioactive microspheres into the blood supply of the tumor, offers a therapeutic option for HCC patients with few alternatives. These innovations underscore a critical shift toward a highly patient-centric approach in the treatment of cancer, including HCC, where minimizing damage to healthy liver tissue is paramount [ 22 , 23 ].…”

90Y SPECT scatter estimation and voxel dosimetry in radioembolization using a unified deep learning framework

“…In recent years, the importance of accurate post-therapy imaging-based dosimetry for RE treatment verification and for establishing dose–response relationships for use in dosimetry-guided treatment planning in future patients has been well recognized [ 2 ]. Furthermore, the concept of using 90Y absorbed dose maps to plan subsequent treatment with external beam radiotherapy (EBRT) to under-dosed regions is being explored [ 3 , 4 ]. Post-therapy dosimetry based on directly imaging the delivered 90Y instead of pre-therapy imaging with surrogates such as 99mTc Macro Albumin Aggregated (99mTc-MAA) is preferred for such application due to differences between predicted and delivered activity distributions.…”