Author: Jason Chiang, Magnus Dahlbom, Veronica Hankil, Xinyi Li, Catherine (Caffi) Meyer, Kyung Hyun Sung 👨🔬
Affiliation: UCLA, University of California, Los Angeles 🌍
Purpose:
Yttrium-90 (90Y) radioembolization is a well-established therapy for large or multifocal liver tumors. Accurate dosimetry is critical but remains challenging, as low particle density risks inadequate tumor coverage while higher density may induce tumor hypoxia. Information on particle density and perfusion is therefore essential to optimize microsphere distribution and improve treatment outcomes. This study aims to quantify the impact of the tumor-to-normal ratio (TNR) and glass microsphere particle density on local progression-free survival (LPFS) following 90Y radioembolization.
Methods:
N=17 patients treated with initial lobar radioembolization using 90Y glass microspheres were included. TNR was measured using 99mTc-MAA SPECT/CT to estimate particle density and tumor perfusion relative to the surrounding liver. Tumor and liver volumes were quantified using MIM Software, and tumor particle density was calculated via a partition model. LPFS was analyzed and optimal TNR and particle density thresholds were identified using a Cox proportional hazards model to minimize p-values.
Results:
The mean particle density was 4568 particles/cm³. The cutoffs that maximize the difference in LPFS are TNR=6.76 (p=0.33) for high and low TNR groups and particle density=7251 particles/cm3 (p=0.15) for high and low particle density. Hypervascular tumors (TNR ≥ 6.76) and tumors that received high particle density radioembolization (particle density ≥ 7251 particles/cm³) were associated with improved LPFS.
Conclusion:
TNR and particle density are important factors influencing LPFS after 90Y radioembolization. These findings highlight the importance of understanding tumor vascularity and optimizing microsphere distribution to enhance 90Y radioembolization outcomes. Although limited by the small sample size, the study provides insights into the relationship between tumor vascularity, particle density, and treatment outcomes, with promising trends observed for improved LPFS in hypervascular tumors and higher particle density treatments. Additional studies with larger cohorts can fully realize the potential of understanding the optimization of particle density to improve survival outcomes.