Tumor volume, FDG uptake, and Tumor dose in correlation with treatment volume change after Y-90 radioembolization in patients with hepatocellular carcinoma

Objectives In patients with hepatocellular carcinoma (HCC), we estimated tumor volume on computed tomography (CT), F-18 Fluorodeoxyglucose (FDG) uptake on positron emission tomography (PET/CT) at baseline, and tumor dose of Y-90 on PET/CT one day after Y-90 microsphere radioembolization (RE). We then assessed these variables in predicting tumor volume changes at 3months post-treatment.

Methods We retrospectively analyzed contrast enhanced CT, FDG PET/CT, and Y-90 PET/CT images of 26 patients (F:M=6:20, a mean age of 55.6 yr) who underwent Y-90 RE. The percentage change of tumor volume (dV) from baseline to 3 months follow-up CT after RE was calculated. The maximum standardized uptake value (SUV_max) of the tumor was divided by the mean SUV of background liver (T/L_SUV) on PET/CT. Voxel dosimetry was performed on Y90 PET/CT, and dose to the tumor and dose-volume histogram (DVH) were obtained. Tumor volume fraction received greater than 100Gy (TF₁₀₀) was estimated from the DVH. Relationships between baseline tumor volume, T/L_SUV at baseline, TF₁₀₀, and dV were assessed by linear regression analyses.

Results Baseline tumor volume showed a marginally significant inverse relationship with dV (r=0.383, p=0.053). T/L_SUV also revealed an inverse relationship (r=0.499, p=0.009). In contrast, TF₁₀₀ had a positive relationship with dV (r=0.496, p=0.01). In fact, TF₁₀₀ showed significant inverse relationships with baseline tumor volume and T/L_SUV (p<0.01 for each, r=0.552 for baseline tumor volume and r=0.499 for T/L_SUV), suggesting better response to Y-90 RE in smaller tumors with lower FDG uptake.

Conclusions TF₁₀₀ calculated by Y-90 PET/CT based dosimetry showed a significant positive correlation with dV validating the role of TF₁₀₀ in assuring tumor response. The tumor volumetric and metabolic biomarkers can be important in predicting TF₁₀₀ after RE.