Predictive value of [99mTc]Tc-MAA SPECT/CT personalised dosimetry in 90Y radioembolization of hepatocellular carcinoma: a DOSISPHERE-01 ancillary study.

PURPOSE: The DOSISPHERE-01 study demonstrated a survival benefit for patients treated with 90Y radioembolization using personalised [99mTc]Tc-MAA guided versus standard dosimetry guided treatment. This ancillary analysis complements DOSISPHERE-01 by reporting post-treatment dosimetry and assessing agreement between predictive ([99mTc]Tc-MAA) and post-treatment (90Y) absorbed doses. MATERIALS AND METHODS: All DOSISPHERE-01 patients with both pre-treatment [99mTc]Tc-MAA SPECT/CT and post-treatment 90Y imaging were eligible. Multicompartment dosimetry was performed using two segmentation methods: anatomic (MRI/CT) and count-threshold based (SPECT). Mean normal liver tissue and index-lesion absorbed dose, and dose volume histogram (DVH) metrics were determined using Simplicit90Y (Mirada Medical, Oxford UK). Agreement between [99mTc]Tc-MAA and 90Y absorbed doses was assessed via Bland-Altman and paired-sample analysis, with correlation assessed via linear-regression. RESULTS: Thirty-seven patients were included: 19 from the personalised arm and 18 from the standard dosimetry arm. Pre- and post-treatment absorbed dose differences were not statistically significant for the index lesion (241 Gy vs. 229 Gy, p = 0.15; mean difference 11.9 Gy; 95% LoA - 84.3 to 108.2 Gy), Perfused Volume Normal Liver Tissue (PVNT) (91 Gy vs. 99 Gy, p = 0.14; mean difference - 8.2 Gy; 95% LoA - 71.6 to 55.1 Gy), or DVH metrics (V200, D70, D50) using anatomic segmentation. Corresponding metrics were significantly different using count-threshold segmentation (p < 0.05). For both methods, pre- and post-treatment mean index lesion and PVNT absorbed doses, and V200, D70, D50 were strongly correlated (Pearsons Correlation Coefficient > 0.65, p < 0.05). CONCLUSION: 90Y absorbed dose outcomes in the DOSISPHERE-01 study corresponded closely with [99mTc]Tc-MAA predictive dosimetry, confirming the validity of [99mTc]Tc-MAA for dosimetry-based treatment planning in this clinical scenario. Agreement was maximised using anatomic segmentation.