Dosimetric optimization and evaluation of hepatocellular carcinoma treatment effect prediction in Y-90 radioembolization

Background: Liver transarterial radioembolization (TARE) with 90Y microspheres is a common treatment for hepatocellular carcinoma (HCC). A pre-treatment SPECT/CT dosimetric study is performed using 99mTc macroaggregated albumin, followed by PET-based dosimetry to assess dose distribution of 90Y. Recent studies show a significant correlation between absorbed doses and treatment outcomes in terms of radiological response, adverse events and overall survival. This study aims to present optimized TARE dosimetry protocols and assess outcome predictions according to voxel-based dosimetry. Methods: Dosimetry protocols were refined according to EANM guidelines using the Planet Dose software. Pre-treatment dosimetry was conducted for all patients while post-treatment dosimetry was performed for patients treated after the installation of a new PET/CT system. Statistical analysis was employed to evaluate predictors of complete radiological response (CR) and survival outcomes. Results: 133 HCC patients treated with 90Y microspheres (95 resin, 38 glass) at single institution were analyzed. ROC curve analysis for resin microspheres indicated a dose threshold of 233.2 Gy (AUC = 0.62) as the best predictor for CR, with higher CR rates in patients receiving this dose. No lung toxicity was noted nor correlation was found between doses to normal liver tissue and adverse events. Conclusions: Lesion absorbed dose is a significant predictor of CR in resin microspheres, with a mean dose of at least 233.2 Gy leading to better oncologic response rates. The absence of correlation between healthy liver tissue dose and adverse events suggests the potential for further increasing the dose to achieve event better outcomes in future protocols.