Radioembolization Research Articles

PD28 Cost-Effectiveness Of Selective Internal Radiation Therapy Using Y-90 Resin Microspheres For Unresectable Hepatocellular Carcinoma In Brazil

IntroductionHepatocellular cancer (HCC) is a severe condition with poor prognosis and a significant burden. Selective internal radiation therapy (SIRT) is recommended as an alternative treatment option to overcome some limitations of current treatments. This analysis estimated the cost-effectiveness of SIRT using Y-90 resin microspheres for the treatment of unresectable HCC in Brazil.MethodsThis study was conducted from the Brazilian payer perspective according to local guidelines, with a lifetime horizon. The use of SIRT in patients with intermediate- or advanced-stage HCC, without extrahepatic disease and ineligible to transarterial chemoembolization, was compared with sorafenib, the commonly used HCC systemic treatment in Brazil. A sensitivity analysis included the subgroup of patients with low tumour burden and preserved liver function.A partitioned-survival model was developed, which included a tunnel state for patients downstaged to receive a treatment with a curative intent such as liver surgery, transplantation or ablation. Survival curves, utilities and adverse events incidence were extracted from published sources of pivotal randomized control trials. Effectiveness of health interventions was measured in quality-adjusted-life-years (QALYs) and life-years (LYs). Local costs from Brazil were applied. Future costs and effects were discounted at five percent. A willingness-to-pay threshold of USD 53,936 was used, based on a 2017 review of healthcare technology adoption in Brazil.ResultsLYs and QALYs were higher for SIRT using Y-90 resin microspheres versus sorafenib (0.27 and 0.20 incremental LYs and QALYs, respectively) and costs were slightly higher for SIRT (USD 3,056 incremental costs). The incremental cost-effectiveness ratio (ICER) was USD 14,948 per QALY in the basecase.One-way and probabilistic sensitivity analyses confirmed the robustness of the analyses. Scenario analyses tested different model assumptions and reinforced the basecase results indicating that SIRT using Y-90 resin microspheres was highly likely to be cost-effective compared with sorafenib. Also, the ICER was lower in the subgroup compared with the overall population.ConclusionsSIRT using Y-90 resin microspheres represents a cost-effective option compared with sorafenib in Brazil.

PD32 Cost-Utility Of Selective Internal Radiation Therapy Using Y-90 Resin Microspheres For Chemotherapy-Refractory Metastatic Colorectal Cancer In Brazil

IntroductionThere were an estimated 55,102 new cases of colorectal cancer (CRC) in Brazil in 2020, comprising 9.3 percent of all newly diagnosed cancers, and making it the third most common cancer in the Brazilian population. Up to half of all patients with CRC will develop liver metastases, and the prognosis for these patients is poor. The objective of the present analysis was to evaluate the cost-utility of selective internal radiation therapy (SIRT) using Y-90 resin microspheres versus best supportive care (BSC) in patients with unresectable, liver-dominant, chemotherapy-refractory metastatic CRC (mCRC).MethodsA three-state partitioned survival model was developed in Microsoft Excel to evaluate the cost-utility of SIRT using Y-90 resin microspheres versus BSC. Membership of the three model states of pre-progression, post-progression and death was governed by parametric models of Kaplan-Meier data from a retrospective, interventional study. Costs associated with SIRT using Y-90 resin microspheres, BSC, and adverse events were obtained from Brazilian sources and reported in 2021 United States dollars (USD). Future costs and effects were discounted at 5 percent. One-way and probabilistic sensitivity analyses (PSA) were performed. A willingness-to-pay threshold of USD 53,936 was used based on a 2017 review of Brazilian healthcare technology adoption.ResultsThe base case analysis showed that Y-90 resin microspheres would result in an increase of 0.76 QALYs versus BSC, increasing quality-adjusted life expectancy from 0.67 QALYs to 1.43 QALYs. The improvement in quality-adjusted life expectancy was accompanied by an increase in costs from USD 9,884 to USD 40,399 over the model time horizon, corresponding to an increase of USD 30,515, and yielding an incremental cost-utility ratio (ICUR) of USD 40,265 per QALY gained. PSA showed there was a 90.8 percent likelihood of cost-effectiveness at USD 53,936 per QALY gained.ConclusionsSIRT using Y-90 resin microspheres was cost-effective versus BSC in the treatment of unresectable, liver-dominant mCRC patients and should be considered for incorporation in the Brazilian Private Healthcare System.

EE350 Selective Internal Radiation Therapy Using Y-90 Resin Microspheres vs Conventional Transarterial Chemoembolization in Barcelona Clinic Liver Cancer Stage B Hepatocellular Carcinoma: A Budget Impact Analysis in England

Selective internal radiation therapy (SIRT) is a well-tolerated treatment for hepatocellular carcinoma (HCC) that has been investigated extensively in patients with HCC in Barcelona Clinic Liver Cancer (BCLC) stage B. The present analysis aimed to evaluate the budgetary implications of using SIRT versus conventional transarterial chemoembolization (cTACE) in treating patients with BCLC B HCC in England.

Selective Internal Radiation Therapy (SIRT) treatment for Liver Cancer

Selective Internal Radiation Therapy (SIRT) treatment for Liver Cancer

EE566 Cost-Effectiveness and Budget Impact Analysis of Selective Internal Radiation Therapy Versus Atezolizumab Plus Bevacizumab From a German Statutory Health Insurance Perspective

Non-metastasized, non-resectable hepatocellular carcinoma (HCC) in patients with Barcelona clinic liver cancer (BCLC) stages B and, in part, C (≈25%) can be treated by systemic immunotherapy or selective internal radiation therapy (SIRT). Therapies vary in terms of required infrastructure, medical specialization(s), facilities, preparation, conduct, and cost. Our objective was to undertake a cost-effectiveness analysis (CEA) and budget impact analysis (BIA) of SIRT – here: with 90Y-labelled glass microspheres (TheraSphere®) compared to immunotherapy with atezolizumab plus bevacizumab (A+B) – from the perspective of the German statutory health insurance (SHI).

EE191 A Budget Impact Analysis of Selective Internal Radiation Therapy Using Y-90 Resin Microspheres Versus Atezolizumab-Bevacizumab as First-Line Therapy in Barcelona Clinic Liver Cancer Stage C Hepatocellular Carcinoma in England

EE191 A Budget Impact Analysis of Selective Internal Radiation Therapy Using Y-90 Resin Microspheres Versus Atezolizumab-Bevacizumab as First-Line Therapy in Barcelona Clinic Liver Cancer Stage C Hepatocellular Carcinoma in England

An Optimized Methodology for Patient-Specific Therapeutic Activity Administration in Liver Radioembolization

Radioembolization (RE) with glass microspheres (MS) loaded with Yttrium-90 (90Y) has been used to treat tumors in the liver with some reported success. However, assessing absorbed doses (AD) in the planning tumor volume (PTV) and normal liver volume (NLV) is a key problem to address in RE. In clinical practice, the computation of 90Y activity to be administered follows the manufacturer’s recommendations, which do not consider the specific characteristics of MS deposition in each patient’s liver. Our main aim is to develop a methodology to estimate the optimal activity for each patient treatment. It uses the absorbed dose distribution (ADD) derived from the Technetium-99m (99mTc)-labeled macroaggregated albumin (MAA) obtained from pre-treatment planning single-photon emission computed tomography (SPECT) images. Post-treatment positron emission tomography (PET) images of the 90Y-MS distribution were used to estimate the ADD for treatment verification. Sixteen RE treatments were retrospectively selected. The agreement between the estimated mean AD based on the planning imaging and real post-treatment mean AD was good in PTV with an intraclass correlation coefficient (ICC) of 0.79 and excellent in NLV (ICC = 0.97). The optimization of 90Y activity using pre-defined clinical AD thresholds (<70 Gy in NLV and >80 Gy in PTV) imposed on the PTV and NLV voxels showed remarkably high agreement (ICC = 0.96, p < 0.001) in eleven out of the sixteen RE treatments between SPECT-MAA-based and PET-MS-based optimal activity estimates. In conclusion, under well-controlled conditions, pre-treatment SPECT-MAA imaging predicts well the treatment of ADD. In addition, SPECT-MAA imaging can be used to optimize the 90Y-MS activity to be administered to the liver.

Improving 90Y PET Scan Image Quality Through Optimized Reconstruction Algorithms.

This study aimed to improve the quality of 90Y PET imaging by optimizing the reconstruction algorithm. Methods: We recruited 10 patients with neuroendocrine tumor metastatic to the liver or primary hepatocellular carcinoma who were qualified for 90Y-labeled selective internal radiation therapy or peptide receptor radionuclide therapy. They underwent posttherapeutic PET/CT imaging using 3 different reconstruction parameters: VUE Point HD with a 6.4-mm filter cutoff, 24 subsets, and 2 iterations (algorithm A); VUE Point FX with a 6.0-mm filter cutoff, 18 subsets, and 3 iterations using time of flight (algorithm B); and VUE Point HD (LKYG) with a 5-mm filter cutoff, 32 subsets, and 1 iteration (algorithm C). The reconstructed PET/CT images were assessed by 10 nuclear medicine physicians using 4-point semiqualitative scoring criteria. A P value of less than 0.05 was considered significant. Results: The median quality assessment scores for algorithm C were consistently scored the highest, with algorithms A, B, and C, scoring 3, 2, and 4, respectively. The 90Y PET scans using algorithm C were deemed diagnostic 91% of the time. There was a statistically significant difference in quality assessment scores among the algorithms by the Kruskal-Wallis rank sum test ([Formula: see text] = 86.5, P < 0.001), with a mean rank quality score of 130.03 for algorithm A, 109.76 for algorithm B, and 211.71 for algorithm C. Subgroup analysis for quality assessment scoring of post-peptide receptor radionuclide therapy imaging alone showed a statistically significant difference between different scanning algorithms ([Formula: see text] = 35.35, P < 0.001), with mean rank quality scores of 45.85 for algorithm A, 50.05 for algorithm B, and 85.6 for algorithm C. Similar results were observed for quality assessment scoring of imaging after selective internal radiation therapy ([Formula: see text] = 79.90, P < 0.001), with mean ranks of 82.33 for algorithm A, 55.79 for algorithm B, and 133.38 for algorithm C. Conclusion: The new LKYG algorithm that was featured by decreasing the number of iterations, decreasing the cutoff of the filter thickness, and increasing the number of subsets successfully improved image quality.

Advances in Delivery of Selective Internal Radiation Therapy (SIRT): Economic and Logistical Effects of Same-Stay Work-Up and Procedure in the Treatment of Unresectable Liver Tumors in England.

Selective internal radiation therapy (SIRT) is a targeted method of treatment for unresectable liver tumors in which radiation therapy is directly delivered to the tumor(s) via the hepatic vasculature. Successful outcomes with SIRT are dependent on the specific vasculature of the liver and tumor, and the patient therefore needs to attend a "work-up" to map the hepatic vasculature prior to the SIRT procedure. Recent advances in SIRT delivery have enabled same-day or same-stay work-up and procedure, requiring only one hospital visit rather than two. We aimed to evaluate the economic, travel time, and transport-related environmental impact of a new brachytherapy device delivery program, the order-map-treat (OMT) program, in patients with unresectable hepatocellular carcinoma (HCC) in England. A healthcare resource group (HRG)-based analysis of costs from a national payer (Department of Health and Social Care, DHSC) perspective was conducted assuming that, with OMT, patients would have to attend hospital only once for both the SIRT work-up and procedure versus twice without OMT. Patient travel time and CO2 emissions were then estimated by identifying the SIRT center closest to the centroid of each clinical commissioning group (CCG) and calculating straight-line distances with a "detour index" to capture the effect of indirect routes via road or rail. It was estimated that 856 patients per annum would be eligible for SIRT treatment for unresectable HCC in England. OMT would be anticipated to save GBP2842 per patient versus performing SIRT without OMT. Furthermore, across all patients with HCC eligible for SIRT in England, OMT would avoid 74,500km of travel, 2299h of travel time, and 13.9 metric tons of patient transport-related CO2 emissions annually. OMT reduces the number of hospital visits required for SIRT by 50%, resulting in financial savings from the DHSC perspective, time savings from the patient perspective, and reduced CO2 emissions arising from patient transport.

Nivolumab after selective internal radiation therapy for the treatment of hepatocellular carcinoma: a phase 2, single-arm study

PurposeTo evaluate the safety and efficacy of selective internal radiation therapy (SIRT) in combination with a PD-1 inhibitor in patients with unresectable hepatocellular carcinoma (uHCC) and liver-only disease ineligible for...

Friday, June 17, 20222:30 PM - 3:30 PM PHSPP01 Presentation Time: 2:30 PM: Dosimetry for Beta Emitting Brachytherapy Sources

<h3>Purpose</h3> Dosimetry for photon-emitting brachytherapy sources is well established, to the point of commercial software for clinical treatment planning to account for material heterogeneities and patient-specific radiation scatter conditions. However, dosimetry standards for beta sources are simpler and have not been recently investigated. While the AAPM TG-149 and ICRU 72 Reports issue clinical guidance and reference data, a modern evaluation of beta-source dosimetry is missing. This investigation strives to identify the potential role for beta-emitting radionuclides as well as to examine theoretical sources for a deeper understanding of beta dosimetry. <h3>Materials and Methods</h3> Available beta-emitting brachytherapy sources include P-32, Sr/Y-90, and Ru/Rh-106 with Y-90 commonly used for selective internal radiation therapy (SIRT) of cancers in the liver. Energy spectra of these sources were taken from ICRU 72 with dose simulations performed using the MCNP v6.2 Monte Carlo radiation transport code. From ICRU 72, the maximum energies for P-32, Sr/Y-90, Y-90, and Ru/Rh-106 were 1.71, 2.28, 2.28, and 3.54 MeV, respectively. Monoenergetic sources of 0.5, 1, 1.5, 2, 3, and 4 MeV were also simulated to extend the energy range and scrutinize dose-distribution dependence on electron energy. Since 2D dose distribution are highly dependent on the design of a source, point sources were simulated to evaluate the depth-dose distribution as a function of radius, <i>r</i>, as well radial dose functions that removed the inverse-square effect. Dose was sampled in 15 cm diameter spheres comprised of water, tissue (ICRU 44 skeletal muscle), or bone (ICRU 44 cortical bone). To mass density effect was quantified in water for 0.5, 1, and 2 g/cm³ with 1 and 2 g/cm³ for tissue and bone, respectively. Observed dose differences were then ascribed to medium differences and not confounded by small differences in mass density. Dose was sampled with radial increments from 0.001 to 0.02 cm for direct comparisons to ICRU 72 results and to evaluate the effect of volume averaging. While only electron sources were considered, dose contributions from bremsstrahlung photons were quantified through comparing results of electron- and electron:photon-transport. Energy deposition was calculated using the MCNP *F8 pulse-height tally, then dividing by the voxel mass to obtain absorbed dose per electron history. With 10⁷ source electrons, statistical uncertainties (<i>k</i>=1) were <0.1% for <i>r</i><0.7 CSDA. When studying bremsstrahlung, 10⁸ source electrons produced 4% statistical uncertainties for <i>r</i>>1.2 CSDA. <h3>Results</h3> In the high dose-gradient region for radionuclide-based beta emitters, the calculated dose distributions in water were within 20% of those from the ICRU 72 Report, which used binned monoenergetic sources to approximate the continuous beta spectra. The radionuclide-based sources exhibited radial dose functions in water that diminished much more steeply than Pd-103, similar to a <0.01 MeV photon source. Sr/Y-90 had a bimodal distribution. Radial dose functions for radionuclide-based sources were inversely proportional to changes in mass density, differing from the scaling-factor models by Cross (1967) and the ICRU 56 Report over the large range of media and densities examined herein. Further, radial dose functions for monoenergetic sources demonstrated a Bragg peak with dose enhancement at <i>r</i>∼0.7 CSDA for all studied energies and media. A sampling of results for radionuclides and monoenergetic sources in water is given in the figure. <h3>Conclusions</h3> Beta dosimetry is largely governed by the mass density with medium composition being a much lesser effect, unlike for low-energy photons where the photoelectric effect is highly sensitive to <i>Z</i>_eff. Unlike for high-energy photon dosimetry, beta dosimetry is negligibly impacted by radiation scatter conditions due to their short range. While Ru/Rh-106 and Sr/Y-90 are proven for shallow plaque brachytherapy and Y-90 for SIRT, beta-emitting radionuclides do not have adequate range for interstitial implants like prostate brachytherapy since dose uniformity is much worse than with HDR Ir-192 or LDR Pd-103 brachytherapy.

Transarterial Yttrium-90 Radioembolization in Intrahepatic Cholangiocarcinoma Patients: Outcome Assessment Applying a Prognostic Score.

Radioembolization (RE) is a viable therapy option in patients with intrahepatic cholangiocarcinoma (ICC). This study delineates a prognostic score regarding overall survival (OS) after RE using routine pre-therapeutic parameters. A retrospective analysis of 39 patients (median age, 61 [range, 32-82] years; 26 females, 13 males) with ICC and 42 RE procedures was conducted. Cox regression for OS included age, ECOG, hepatic and extrahepatic tumor burden, thrombosis of the portal vein, ascites, laboratory parameters and dose reduction due to hepatopulmonary shunt. Median OS after RE was 8.0 months. Using univariable Cox, ECOG ≥ 1 (hazard ratio [HR], 3.8), AST/ALT quotient (HR, 1.86), high GGT (HR, 1.002), high CA19-9 (HR, 1.00) and dose reduction of 40% (HR, 3.8) predicted shorter OS (each p &lt; 0.05). High albumin predicted longer OS (HR, 0.927; p = 0.045). Multivariable Cox confirmed GGT ≥ 750 [U/L] (HR, 7.84; p &lt; 0.001), ECOG &gt; 1 (HR, 3.76; p = 0.021), albumin ≤ 41.1 [g/L] (HR, 3.02; p = 0.006) as a three-point pre-therapeutic prognostic score. More specifically, median OS decreased from 15.3 months (0 risk factors) to 7.6 months (1 factor) or 1.8 months (≥2 factors; p &lt; 0.001). The proposed score may aid in improved pre-therapeutic patient identification with (un-)favorable OS after RE and facilitate the balance between potential life prolongation and overaggressive patient selection.

Overall Survival after Y-90 Selective Internal Radiotherapy of Liver Metastases in Oligometastatic Patients

<h3>Purpose/Objective(s)</h3> Y-90 Selective Internal Radiotherapy (SIRT) is an ablative therapy used for patients with inoperable liver metastasis. The purpose of this investigation was to examine the impact of local control after SIRT on overall survival (OS) in oligometastatic patients, hypothesizing that local failure after SIRT would be correlated with lower OS. <h3>Materials/Methods</h3> A retrospective, single-institution, IRB-approved study selected oligometastatic patients defined as 5 or fewer total non-CNS metastases at the time of unilateral or bilateral lobar Y-90 SIRT from 2009 to 2021. Patients were staged with CT and/or MRI. The primary endpoint was OS defined from Y-90 SIRT completion to date of death or last follow-up. Local failure was classified as progressive disease at the target lesion(s) by RECIST v1.1 criteria starting at 3 months after SIRT. Failure was defined by imaging or if salvage locoregional therapy was performed. OS outcomes were calculated using the Kaplan-Meier method, and correlations with clinical variables were evaluated using log-rank testing. <h3>Results</h3> Twenty-three oligometastatic patients, with a total of 57 liver lesions, completed SIRT. The cohort was comprised of patients with colorectal adenocarcinoma (n=15), pancreatic adenocarcinoma (n=6), thymic carcinoma (n=1), and uveal melanoma (n=1). Fifteen patients (65%) received bilateral lobar SIRT and 8 (35%) received unilateral lobar treatment. Median follow up was 15.6 months (range 2.7-54.3). Twenty patients were treated with resin Y-90 microspheres and 3 received glass microspheres. On volumetric analysis of liver tumor burden, the range of liver involvement was 0.03% to 18.2%. The range of liver metastases was 1 to 5 with a median of 3. Of the 57 individual lesions treated, 19 (33%) failed. Fourteen patients (61%) failed in a treated lesion, including 9 as the first site of failure. Seven patients received salvage liver-directed therapy following intrahepatic failure; six received repeat SIRT. Seven patients did not receive post-SIRT chemotherapy, of which 5 experienced intralesional failure. Median OS (mOS) was 20.1 months, and 12-month OS was 68.6%. Metachronous versus synchronous metastasis at presentation was not found to be prognostic of OS (21.7 months vs 17.9 months (p<0.96)). Those with tumor involving <5% of the liver (n=17) had a mOS of 21.7 months vs 15.1 months for those with >5% (n=6) (p<0.12). Intralesional failure was associated with worse mOS (15.1 months vs. not reached, p<0.03). <h3>Conclusion</h3> These results suggest that intralesional failure following Y-90 may be associated with inferior OS, emphasizing the importance of disease control in low metastatic burden patients. Percentage of liver involvement may be predictive of local failure after SIRT. Larger prospective studies examining oligometastatic patients treated with SIRT are needed for further patient risk stratification.

A Workflow for Dosimetry of 90Y Radioembolization Based on Quantitative 99mTc-MAA SPECT/CT Imaging and a 3D-Printed Phantom

At a time of increasing evidence for dose-effect relationships in radioembolization (RE) with 90Y-microspheres, the general consensus is that there is an urgent need for accurate treatment planning and dose assessment in patients undergoing RE treatment. This work aimed at assessing the usefulness of 99mTc macroaggregated albumin (MAA) SPECT/CT imaging for personalized provisional RE dosimetry considering a 3D-printed patientlike phantom (AdboMan phantom). A homemade tool was developed in MATLAB for image analysis and absorbed dose calculation. Two dose calculaton methods were implemented and used to calculate dose volume histograms: (I) dose kernel method and (II) local energy deposition method. The accuracy of the two different dosimetric methods was evaluated by means of 3D γ-index (1%–1 mm and 2%–2 mm) implemented in the tool. Differences between the two dose calculation methods using the 3D γ-index are within 1%–1 mm and 2%–2 mm for all AbdoMan inserts, with a passing rate of 99.9% and 100%, respectively, proving a good agreement between the two calculation methods. The present study supports the use of 99mTc-MAA SPECT acquisition for provisional dosimetry along with the local energy deposition method to convert reconstructed SPECT data into absorbed dose maps. As long as 99mTc-MAA SPECT acquisitions are performed on liver lesions larger than 40 mm, the absorbed dose computed by means of the local energy deposition method can lead to results in line with those obtained by Monte Carlo calculations.

The inhibiting effect of alpha-based TARE on embolized vessels and neovascularization.

Transarterial embolization (TAE) is a personalized technology that offers precise delivery of chemotherapeutic drugs or selective internal radiation therapy for hepatocellular carcinoma (HCC). Beta-emitting radionuclide embolisms for TAE (β-based TARE) are commonly used in the clinic via inducing biochemical lethality on tumor cells, while alpha-emitting radionuclides-based embolisms for TAE (α-based TARE) are still under study. The feeding artery plays a key role in tumor growth, metastasis, and recurrence. In this research, the auricular central arteries (ACAs) of rabbits were embolized with silk fibroin-based microspheres (SFMs) or SFMs integrated with α (Ra-223) or β (I-131) radionuclides to investigate the influence on vessels. TARE-induced tissue necrosis and the following neovascularization were measured by pathological analysis and 68Ga-DOTA-RGD PET/CT. The results showed that, compared to I-131, Ra-223 enhanced the growth inhibition of human hepatoma cells Huh-7 and induced more DNA double-strand breaks in vascular smooth muscle cells. Unlike β-based TARE, which mainly led to extensive necrosis of surrounding tissues, α-based TARE induced irreversible necrosis of a limited area adjacent to the embolized vessels. RGD PET revealed the inhibition on neovascularization in α-based TARE (SUVmax = 0.053 ± 0.004) when compared with normal group (SUVmax = 0.099 ± 0.036), the SFMs-lipiodol group (SUVmax = 0.240 ± 0.040), and β-based TARE (SUVmax = 0.141 ± 0.026), owing to the avoidance of the embolism-induced neovascularization. In conclusion, α-based TARE provided a promising strategy for HCC treatments via destroying the embolized vessels and inhibiting neovascularization.

Optimization of 99mTc-MAA SPECT/CT Imaging for 90Y Radioembolization Using a 3D-Printed Phantom

Radioembolization (RE) with 90Y-microspheres has gained widespread acceptance as a safe and effective technique for treating liver malignancies. Accurate quantification in RE is a key step in treatment planning optimization and is becoming a pressing issue in light of the Directive 2013/59/EURATOM. The aim of this study was to develop a SPECT/CT imaging protocol for quantitative imaging optimization in RE based on cutting edge imaging technology (Symbia IntevoTM system provided with the innovative xSPECT software) and a novel anthropomorphic 3D-printed phantom. In the present study, 99mTc-labeled macroaggregated albumin was used as a surrogate radiopharmaceutical for treatment planning. Gamma camera calibration factors and recovery coefficients were determined performing preliminary SPECT/CT acquisitions of a point source, a cylindrical homogeneous phantom and the NEMA/IEC phantom. Data reconstruction was performed using the built-in xSPECT package, using both the Ordered Subset Expectation–Maximization (OSEM) and the Ordered Subset Conjugated Gradient (OSCG) algorithm. Specific regions of interest (ROIs) were drawn on the MIM 6.1.7 system according to the physical volume. The quantification procedure was validated using the anthropomorphic phantom provided with a fillable liver section and spheres of different diameters (20 mm, 40 mm and a 40 mm spherical shell). The measured activity concentration in all geometries is consistent within 4%, demonstrating that the xSPECT software permit an absolute quantification in anthropomorphic geometry largely within the 10% recommended from the manufacturer. Caution is advised in the presence of spherical objects with a necrotic core, as underestimations in the order of 20% were obtained.

Letter to the Editor From Hallanger Johnson and El-Haddad: "Yttrium-90 Selective Internal Radiation Therapy Plus Cryoablation for Recurrent Adrenocortical Carcinoma With Liver Metastases".

Letter to the Editor From Hallanger Johnson and El-Haddad: "Yttrium-90 Selective Internal Radiation Therapy Plus Cryoablation for Recurrent Adrenocortical Carcinoma With Liver Metastases".

S1383 Patient Survival and Tumor Responses in Patients Undergoing Radiation Segmentectomy: A Large Tertiary Center Experience

Introduction: UnresecTable hepatocellular carcinoma (HCC) can be treated with Selective Internal Radiation Therapy (SIRT) with Y-90, using either SIR-Spheres® (SS) or TheraSpheres® (TS). The aim of this study was to report the tumor response, overall survival, and tolerability of SS and TS. Methods: We retrospectively analyzed charts of 137 patients who underwent SIRT with SS or TS at our center from April 2017 to January 2021, comprising 210 total procedures. Statistical analysis was performed using SAS. Results: Stratification by therapy type showed 70% of total Y-90 therapy procedures were with SS and 30% with TS. Table contains the demographic breakdown, liver disease etiology, tumor characteristics, MELD score, BCLC stage, pre- and post-SIRT symptoms, and Modified Response Evaluation Criteria in Solid Tumors (mRECIST) for SS and TS. There was a decrease in size, enhancement, or both size and enhancement in 85% of SS and 88% of TS patients. The median overall survival was 18 months for SS and 20 months for TS. Tumor recurrence occurred in 26% of non-transplanted patients while 3 transplanted patients (out of 15) showed recurrence. The median injected dose of Y-90 SS (24.9 mCi, range 5.7-81.8 mCi) was significantly lower than that of Y-90 TS (39.6 mCi, range 4.6-90.1 mCi). This is likely due to different dosimetry models for each type of bead, which evolve as imaging modalities allow more accurate representations of absorbed radiation per dose. The procedures were well tolerated. Conclusion: Our findings indicate that intermediate and advanced HCC patients have excellent response to Y-90 therapy with both SS and TS, as depicted by the decrease in size, enhancement, or both in 85% (SS) and 88% (TS) of patients, complete response in 37% (SS) and 49% (TS) of patients, and overall survival that ranges from 18 (SS) to 20 (TS) months, which is very favorable in this group of patients. Therapy is very well tolerated. Differences between SS and TS may possibly be explained by dosimetry; however, further comparative studies may be needed. Table 1. - Patient Demographic, Disease, and Tumor Characteristics by Treatment Type SIR-Spheres® (SS) TheraSpheres® (TS) Procedures 147 63 Gender Male 73% 62% Female 27% 38% Race Caucasian 56% 52% African American 20% 21% Hispanic or Latino 21% 22% Asian 3% 5% Etiology of Liver Disease Hepatitis C 55% 46% Non-alcoholic Steatohepatitis (NASH) 24% 25% Other 21% 29% Tumor Characteristics Number of Lesions (median) 3 2 Total Tumor Diameter (median) 6.4 cm 5.1 cm Bilobar Tumors 61% 31% Portal Vein Thrombosis 46.9% 25.4% Model for End-Stage Liver Disease (MELD) Score Score (median) 9 8 Barcelona Clinic Liver Cancer (BCLC) Stage Stage 0 1% 3% Stage A 11% 13% Stage B 45% 43% Stage C 38% 35% Stage D 5% 6% Associated Symptoms Pre-Treatment Ascites 16% 16% GI Bleed 16% 22% Hepatic Encephalopathy 17% 17% Associated Symptoms Post-Treatment Ascites 29% 16% GI Bleed 3% 2% Hepatic Encephalopathy 8% 0% Modified Response Evaluation Criteria in Solid Tumors (mRECIST) Complete Response 37% 49% Partial Response 21% 25% Stable Disease 21% 10% Progressive Disease 20% 16%

Effect of tumour involvement on activity determination of resin Yttrium-90 in selective internal radiation therapy of metastatic liver cancer

Abstract Introduction: The study was aimed to evaluate the effect of tumour involvement on resin Yttrium-90 (Y90) activity determination for metastatic liver cancer treatment. Methods: One hundred and two cases of resin Y90 microsphere treatment were retrospectively studied. Body surface area (BSA) method was used in the calculation of resin Y90 activity. The total activity (TA) was calculated as a summation of activities obtained from BSA-based calculation and tumour involvement (TI). TI and TA of each case were evaluated. The contributions of TI to TA were calculated with the ratio of TI/TA. Results: The average contribution of TI to TA was 4·1%. The contributions were &lt; 5·8% in 75% of the cases, &lt; 2·2% in 50% of the cases and &lt; 1·0% in 25% of the cases. Conclusions: Overall the effect of tumour involvement on the activity determination was small. The activity calculation could be simplified by neglecting TI in 25% of the cases where the activity contribution from TI was less than 1%. Contouring tumour and liver structures for TI calculation could be avoided in these cases, and the efficiency of the workflow for resin Y90 procedures could be improved.

LiMAx Prior to Radioembolization for Hepatocellular Carcinoma as an Additional Tool for Patient Selection in Patients with Liver Cirrhosis.

Simple SummaryRadioembolization is a well-established therapeutic option for patients with advanced hepatocellular carcinoma. However, patients with advanced tumor disease and presence of liver cirrhosis often present a borderline liver function and are at risk for post-interventional hepatic decompensation. The aim of our study was to evaluate the ability of the LiMAx®, a non-invasive test for liver function assessment, in predicting post-therapeutic hepatic deterioration and thus improve patient selection prior radioembolization.Background and Aims: Radioembolization (RE) has recently demonstrated a non-inferior survival outcome compared to systemic therapy for advanced hepatocellular carcinoma (HCC). Therefore, current guidelines recommend RE for patients with advanced HCC and preserved liver function who are unsuitable for transarterial chemoembolization (TACE) or systemic therapy. However, despite the excellent safety profile of RE, post-therapeutic hepatic decompensation remains a serious complication that is difficult to predicted by standard laboratory liver function parameters or imaging modalities. LiMAx® is a non-invasive test for liver function assessment, measuring the maximum metabolic capacity for 13C-Methacetin by the liver-specific enzyme CYP 450 1A2. Our study investigates the potential of LiMAx® for predicting post-interventional decompensation of liver function. Patients and methods: In total, 50 patients with HCC with or without liver cirrhosis and not amenable to TACE or systemic treatments were included in the study. For patients prospectively enrolled in our study, LiMAx® was carried out one day before RE (baseline) and 28 and 90 days after RE. Established liver function parameters were assessed at baseline, day 28, and day 90 after RE. The relationship between baseline LiMAx® and pre-and post-interventional liver function parameters, as well as the ability of LiMAx® to predict hepatic decompensation, were analyzed. Results: We observed a strong association between baseline LiMAx® and bilirubin, albumin, ALBI grade, and MELD score. Patients presenting with Child–Pugh score B 28 days after RE or with a deterioration in Child–Pugh score by at least one point had a significantly lower baseline LiMAx® compared to those with Child–Pugh score A or with stable Child–Pugh score. The ability of LiMAx® to predict hepatic decompensation after RE was determined using ROC curve analysis and was compared to MELD score and ALBI grade. LiMAx® achieved a substantial AUC of 0.8117, comparable to MELD score and ALBI grade. Conclusion: Patients with lower LiMAx® values at baseline have a significantly increased risk for hepatic decompensation after RE, despite being categorized as Child–Pugh A. Therefore, LiMAx® can be used as an additional tool to identify patients at high risk of post-interventional hepatic failure.