Response to Trans-arterial Radioembolization Therapy for Liver Cancer According to Voxel-Based Dosimetry: A Retrospective Study

Abstract

BackgroundUsual clinical dosimetry models for trans-arterial radioembolization (TARE) is based on assumption of uniform dose distribution in each tissue compartment. We performed a simple voxel-based dosimetry using post-treatment yttrium-90 (90Y) microsphere PET in TARE and investigated the prognostic value of dosimetry parameters from the voxel-based dosimetry.MethodTwenty-eight patients with hepatocellular carcinoma who underwent TARE using 90Y-microsphere were retrospectively included. Mean absorbed dose of each lesion (TDv) was analyzed using voxel-based dose maps derived from posttreatment 90Y-microsphere PET and voxel-wise S-value kernels. Heterogeneity of intra-tumoral absorbed dose was investigated using standard deviation and coefficient of variation of voxel doses in a tumor. The response of each lesion was classified as local control success (LCS) and local control failure (LCF) based on follow-up MRI or CT. Prognostic values of dosimetry parameters and clinicopathologic factors were evaluated using survival analysis for progression-free survival. ResultsFourteen lesions from 10 patients were analyzed. The LCS and LCF groups showed significant differences in TDv and intra-tumoral absorbed dose heterogeneity, but not in the tumor size. Univariate survival analysis identified high serum aspartate transaminase level (> 40 IU/L), large tumor size (> 66 mm), and low TDv (< 81 Gy) as significant prognostic factors. However, on multivariate analysis, only low TDv was identified as an independent predictive factor (P = 0.022; HR, 21.018; 95% CI: 1.549–258.204), with a cutoff value of 80–120 Gy. Spearman’s correlation analysis also showed a significant correlation between TDv and PFS (P = 0.009, r = 0.669). ConclusionsIn TARE using 90Y-microspheres, voxel-wise absorbed dose can be easily estimated on post-treatment 90Y PET using a simple method. The TDv calculated by the voxel-based dosimetry is an effective prognostic factor for PFS with a cutoff value of 80–120 Gy.