Transient flow modulation with rapid-resorbable gelatin microspheres during Yttrium-90 radioembolization for liver cancer: a preliminary clinical trial

Abstract Objectives To explore the effectiveness of rapid-resorbable gelatin microspheres (RGMs) for protecting non-tumorous liver (NTL) through flow modulation during yttrium-90 (Y-90) radioembolization for liver cancer. Materials and methods This phase II trial defined the primary outcome as the protection rate of RGM-embolized vs non-embolized NTL on Y-90 PET/CT. RGMs (560–800 µm) were used to transiently diminish blood flow to the NTL, followed by Y-90 microsphere administration. The effectiveness of flow modulation and radioembolization was assessed using Y-90 PET/CT and gadoxetic acid-enhanced MRI (EOB-MRI). Results Twenty patients were enrolled between March 2023 and January 2025. The median protection rate was 35.8% (interquartile range [IQR], 20.2–66.7). Seven patients (35%, 7/20) demonstrated a ≥ 2-fold increase in the tumor-to-NTL uptake ratio on Y-90 PET/CT compared with pre-treatment SPECT/CT. The signal intensity (SI) ratio between protected and unprotected NTLs on the hepatobiliary phase of EOB-MRI increased significantly from baseline (median, 1.03; IQR, 0.97–1.05) to 6-month follow-up (median, 1.29; IQR, 1.18–1.54; p < 0.001). The Y-90 microsphere load to the NTL was negatively correlated with the protection rate ( ρ = −0.578, p = 0.010), whereas the protection rate was positively correlated with the SI ratio at 6 months ( ρ = 0.710, p = 0.001). All patients who underwent subsequent intra-arterial treatments achieved complete arterial recanalization. Conclusion RGM-mediated flow modulation was associated with reduced Y-90 microsphere deposition in the NTL, with imaging findings suggesting regional liver function preservation. This protective effect appeared greater with lower Y-90 microsphere load. Key Points Question Can flow modulation using RGMS preserve regional liver function ? Findings Prior embolization with rapidly resorbable gelatin microspheres reduced the absorbed dose to the NTL by 35.8% and preserved signal intensity on EOB-MRI after radioembolization . Clinical relevance RGMs can transiently divert arterial flow away from the NTL, reducing Yttrium-90 microsphere influx and helping preserve regional liver function during Yttrium-90 radioembolization for liver cancer .