[Oral Communication] Comparaison entre les Dosimétries Prédictive et Post-Traitement pour les Patients Atteints de Carcinome Hépatocellulaire Traités par Radioembolisation aux Microsphères de Verre*

*Comparison between predictive and post-treatment dosimetry for hepatocellular carcinoma patients treated with ⁹⁰Y-glass microsphere radioembolization

M. Kafrouni^a,b,c, M. Fourcade^a, S. Vauclin^c, A.D. Ilonca^a, D. Mariano-Goulart^a,b, F. Ben Bouallègue^a,b
a Department of nuclear medicine, Montpellier University Hospital/Montpellier/France
b PhyMedExp, University of Montpellier, INSERM, CNRS, Montpellier University Hospital/Montpellier/France
c DOSIsoft SA/Cachan/France

Presented at SFPM 2018

ABSTRACT
Introduction: The aim of this study was to analyze the differences between ^99mTc-MAA SPECT and ⁹⁰Y-microsphere PET dosimetry investigating imaging (spatial resolution, partial volume effect, noise) and clinical factors (catheter positioning, modified vascularization, MAA/microsphere distribution).

Methods: Nineteen ⁹⁰Y-glass microsphere radioembolizations of hepatocellular carcinoma patients were analyzed in this study. For each treatment, predictive and post-treatment doses to tumor and normal liver (NL) were calculated with a dedicated software (PLANET® Dose, DOSIsoft, Cachan, France) applying a convolution method based on voxel-S factors. The mean (±standard deviation) administered activity was 3.5 GBq (±1.2) for a mean tumor volume of 546 mL (±408mL). In addition to the tumor average dose (D_avg), dose metrics extracted from dose volume histograms were analyzed: minimum dose to 70% and 50% of the tumor volume (D₇₀ and D₅₀) and percentage of the tumor volume receiving at least 205 Gy (V₂₀₅), as recommended in the literature for glass-microsphere treatments¹. Difference and correlation between predictive and post-treatment doses were assessed using a paired Student’s t test and Pearson’s correlation coefficient. Spatial concordance analysis at the voxel level between MAA and microsphere distributions is ongoing. This should provide additional information to better understand the part of dose differences related to clinical factors.

Results: Dose results showed a good correlation between ^99mTc-MAA SPECT and ⁹⁰Y-microsphere PET based dosimetry (Table 1). However, difference between them was significant for all tumor and NL dose metrics considered. A ⁹⁰Y-microsphere PET tendency to underestimate ^99mTc-MAA SPECT based doses was observed. Preliminary results indicate that the largest dose discrepancies can be explained by clinical differences in terms of administration procedure and particle distribution.

Conclusion: The overall good correlation observed between predictive and post-treatment dosimetry confirm the MAA predictive value. A tendency of ⁹⁰Y-microsphere PET to underestimate ^99mTc-MAA SPECT doses was observed.