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Radioembolization of liver cancers using 90 Y-loaded microspheres is experiencing more widespread use. However, few data are available concerning the doses delivered to the tumors and the healthy liver. This retrospective study was conducted to calculate the tumor dosimetry (planned tumor dose [T plan D]) and nontumor dosimetry in patients treated by 90 Y-loaded glass microspheres and determine whether tumor dosimetry could predict response and survival. Methods: Thirty-six patients with hepatocellular carcinoma (HCC), including 16 with portal vein thrombosis (PVT), were treated with 90 Y-loaded glass microspheres. The T plan D and the dose delivered to the injected healthy liver were calculated using a quantitative analysis of the 99m Tc-macroaggregated albumin ( 99m Tc-MAA) SPECT/CT exam. Responses were assessed after 3 mo, using the criteria of the European Association for the Study of the Liver. Progression-free survival (PFS) and overall survival (OS) were evaluated using Kaplan-Meier tests. Results: The response rate was 69% for the overall population and 75% for the PVT patients. The dose delivered to the tumor was the only parameter associated with response with multivariate analysis (P 5 0.019). A threshold T plan D value of 205 Gy was predictive of response, with a sensitivity of 100% and an accuracy of 91%. Quantitative 99m Tc-MAA SPECT/CT allowed us to increase the injected activity for 4 patients with large lesions. PFS was only 5.2 mo and OS 9 mo when using a T plan D of less than 205 Gy versus 14 mo (P 5 0.0003) and 18 mo (P 5 0.0322), respectively, with a T plan D of 205 Gy or more. Conclusion: Quantitative 99m Tc-MAA SPECT/ CT is predictive of response, PFS, and OS. Dosimetry based on 99m Tc-MAA SPECT/CT can be used for the selection of patients and for an adaptation of treatment planning, especially in selected patients (particularly in the case of large tumors). These results also confirm the efficacy and safety of 90 Y-loaded microspheres in treating HCC, even in the presence of PVT (and especially when 99m Tc-MAA uptake is seen inside the PVT).

PurposeTo evaluate the impact of dosimetry based on MAA SPECT/CT for the prediction of response, toxicity and survival, and for treatment planning in patients with hepatocellular carcinoma (HCC) treated with 90Y-loaded glass microspheres (TheraSphere®).MethodsTheraSphere® was administered to 71 patients with inoperable HCC. MAA SPECT/CT quantitative analysis was used for the calculation of the tumour dose (TD), healthy injected liver dose (HILD), and total injected liver dose. Response was evaluated at 3 months using EASL criteria. Time to progression (TTP) and overall survival (OS) were evaluated using the Kaplan-Meier method. Factors potentially associated with liver toxicity were combined to construct a liver toxicity score (LTS).ResultsThe response rate was 78.8 %. Median TD were 342 Gy for responding lesions and 191 Gy for nonresponding lesions (p < 0.001). With a threshold TD of 205 Gy, MAA SPECT/CT predicted response with a sensitivity of 100 % and overall accuracy of 90 %. Based on TD and HILD, 17 patients underwent treatment intensification resulting in a good response rate (76.4 %), without increased grade III liver toxicity. The median TTP and OS were 5.5 months (2–9.5 months) and 11.5 months (2–31 months), respectively, in patients with TD <205 Gy and 13 months (10–16 months) and 23.2 months (17.5–28.5 months), respectively, in those with TD >205 Gy (p = 0.0015 and not significant). Among patients with portal vein thrombosis (PVT) (n = 33), the median TTP and OS were 4.5 months (2–7 months) and 5 months (2–8 months), respectively, in patients with TD <205 Gy and 10 months (6–15.2 months) and 21.5 months (12–28.5 months), respectively, in those with TD >205 Gy (p = 0.039 and 0.005). The median OS was 24.5 months (18–28.5 months) in PVT patients with TD >205 Gy and good PVT targeting on MAA SPECT/CT. The LTS was able to detect severe liver toxicity (n = 6) with a sensitivity of 83 % and overall accuracy of 97 %.ConclusionDosimetry based on MAA SPECT/CT was able to accurately predict response and survival in patients treated with glass microspheres. This method can be used to adapt the injected activity without increasing liver toxicity, thus defining a new concept of boosted selective internal radiation therapy (B-SIRT). This new concept and LTS enable fully personalized treatment planning with glass microspheres to be achieved.