International recommendations for personalised selective internal radiation therapy of primary and metastatic liver diseases with yttrium-90 resin microspheres

Yttrium-90 Radioembolization for Intrahepatic Cholangiocarcinoma: Non-University Tertiary Care Center Experience

BackgroundIntrahepatic cholangiocarcinoma (ICC) presents a significant clinical challenge due to its high fatality rate and limited surgical candidacy. With only 30-40% of patients eligible for surgery upon diagnosis, alternative therapies are imperative. This study assesses the efficacy of Yttrium-90 (Y-90) radioembolization for unresectable ICC patients in a non-university tertiary care center (NUTCC).MethodsA retrospective analysis of 15 unresectable ICC patients treated with Y-90 radioembolization was conducted. Tumor response, survival, and adverse events were evaluated using RECIST criteria.Results60% of patients exhibited partial response, and 20% showed stable disease, with notable tumor size reduction and a median survival of 14 months. Minimal adverse effects were observed, indicating Y-90's favorable safety profile.ConclusionY-90 radioembolization shows potential in reducing tumor burden and enhancing survival rates with minimal adverse effects for unresectable ICC. Larger prospective studies are needed to confirm its efficacy and define its role in ICC treatment protocols.

Dose-response relationships in Y90 resin microsphere radioembolization for patients with hepatocellular carcinoma: insights from a Brazilian cohort

OBJECTIVE

To evaluate the relationship between the absorbed dose and radiological response in patients with hepatocellular carcinoma undergoing resin microsphere radioembolization to enhance treatment precision and potentially adjust protocols for better outcomes.

METHODS

This single-center retrospective study was conducted at a quaternary care center in Brazil and comprised 27 patients with 58 target lesions treated between November 2014 and April 2023. The patients' dosimetric profiles were analyzed using advanced imaging software to assess post-treatment clinical and radiological responses. This study explored the correlation between the absorbed doses and tumor objective responses using statistical analyses to confirm the findings.

RESULTS

Higher absorbed doses were significantly associated with improved objective responses in the target lesions. The analysis demonstrated that achieving higher dosimetric thresholds correlated with better clinical outcomes, suggesting that a dose-response relationship is essential to optimize treatment protocols.

CONCLUSION

These findings emphasize the importance of personalized dosimetry in managing hepatocellular carcinoma using resin microsphere radioembolization. By quantifying the absorbed dose and understanding its impact on tumor response, treatment strategies can be tailored to enhance efficacy and potentially shift palliative treatments toward curative outcomes. This study provides a crucial foundation for dosimetric adjustment and highlights the need for further research in this area, particularly in Brazil.

Advances and Emerging Techniques in Y-90 Radioembolization for Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer deaths worldwide. Despite the high incidence of HCC, mortality remains high, with an estimated 5-year survival rate of less than 20%. Surgical resection represents a potential curative treatment for HCC; however, less than 20% of patients with HCC are candidates for surgical resection. In patients with unresectable HCC, Yttrium-90 (Y90) transarterial radioembolization (TARE) has emerged as an innovative treatment option. This locoregional therapy delivers high doses of radiation directly to liver tumors via intra-arterial injection, allowing for the targeted destruction of malignant cells while sparing surrounding healthy tissue. In this review, we will explore the latest advances in Y90 TARE for the treatment of HCC, focusing on key developments such as the following: (1) improvements in radiation lobectomy and segmentectomy techniques, (2) the introduction of personalized dosimetry, (3) the integration of combination therapies, (4) the use of imageable microspheres, (5) pressure-enabled Y90 delivery systems, and (6) the application of Y90 surrogates.

Initial Experience with Single-Session Resin-Based Transarterial Radioembolization Mapping and Treatment of Small Hepatocellular Carcinomas

BACKGROUND/OBJECTIVES

Studies have indicated that forgoing lung shunt fraction measurement in select patients undergoing Yttrium 90 (Y90) transarterial radioembolization (TARE) may be safe without sacrificing efficacy. This study evaluated the safety and efficacy of a streamlined treatment in patients with small hepatocellular carcinoma (HCC) receiving resin-based TARE.

METHODS

Patients who received single-session Y90 TARE between September 2023 and May 2024 were retrospectively evaluated. Treatment response was evaluated at the 3-month follow-up using the modified Response Evaluation Criteria in Solid Tumors (mRECIST) criteria. Adverse events (AEs) ≥ Grade 3 were recorded post-procedurally at 3 months. The time from the interventional radiology clinic visit to the procedure date was compared to patients receiving the conventional TARE treatment.

RESULTS

Ten consecutive patients were treated with 12 treatments. Each treatment targeted an isolated lesion with median size of 2.5 cm (IQR: 2.1, 2.9). Two patients received two treatments (one for treatment of a separate lesion and the other for the initial incomplete targeting of the tumor). The median delivered tumor dose was 377.7 Gy (IQR: 246.5, 570.1). No patients developed ≥ Grade 3 AEs post-TARE. Complete response was achieved in 11/12 patients (92%). The conventional cohort consisted of 60 patients, all OPTN T2 treated with radiation segmentectomy with glass microspheres. Patients undergoing SSMT had a median time from clinic visit to treatment of 26.5 days (IQR: 15.3, 39) vs. 61 days (IQR: 48, 88.8) in the conventional TARE group (p < 0.001).

CONCLUSIONS

Streamlined single-session resin-based Y90-TARE in patients with OPTN T2 stage HCC is feasible, efficacious, safe, and associated with reduced time to treatment.

Radioembolization for Hepatocellular Carcinoma: a Comparison on Dual-phase Cone-beam CT, Contrast-enhanced CT (CECT) and 99mTc-macroaggregated albumin-SPECT/CT in predicting final distribution volumes and dosimetry of the post-embolization 90Y PET/CT

PURPOSE

Personalized treatment schemes are being systematically applied to ensure best treatment outcome in oncologic patients. This is true also for personalized dosimetry in transarterial radioembolization (TARE) in hepatocellular carcinoma (HCC) patients. Precise and detailed volumetric and functional data derived from radiological and nuclear imaging methods are essential for personalized dosimetry. We sought to evaluate accuracy of dual-phase cone-beam CT (CBCT) in comparison to pre-treatment contrast-enhanced CT (CECT), and 99mTc-macroaggregated albumin-SPECT/CT ([99mTc]MAA SPECT/CT) to predict and assess the efficacy of TARE based on post-treatment 90Y PET/CT.

MATERIAL AND METHODS

Thirty consecutive patients with HCC treated with TARE were included. Intraprocedural dual-phase CBCT acquisition protocol was developed to distinguish tumor volume in the early arterial phase and perfused volume of non-affected liver in the late arterial phase. Volumetric data obtained from pre-treatment CECT, dual-phase CBCT and [99mTc]MAA SPECT/CT were compared to post-treatment 90Y PET/CT considered the standard reference. Treatment simulations for final calculated dose from the different imaging derived volumes were then compared to post-treatment 90Y PET/CT.

RESULTS

CBCT resulted as the most accurate method in predicting tumor- (R2 0.88) and perfused volumes (R2 0.82). Dosimetry prediction planning performed on derived volumes from the different methods did not show significant difference (p < 0.05), yet highest concordance with 90Y PET/CT data was observed with dual-phase CBCT.

CONCLUSION

Our study shows that dual-phase CBCT acquisition is a novel alternative method for correctly and safely administering more accurate and defined doses during TARE.

CLINICALTRIALS

gov ID: NCT03981497.

Hepatocellular Carcinoma with Vascular Invasion Treated with Resin Yttrium-90 Transarterial Radioembolization Using Single Compartment Dosimetry

PURPOSE

To report outcomes in hepatocellular carcinoma (HCC) patients with lobar and segmental vascular invasion treated with resin Yttrium-90 transarterial radioembolization (Y90-TARE) with single-compartment MIRD (Medical Internal Radiation Dose) model.

MATERIALS AND METHODS

This was a retrospective IRB approved study of patients with a diagnosis of HCC with vascular invasion undergoing resin Y90-TARE from 2014 to 2022 (n = 61). Patients with Body Surface Area dosimetry (n = 20), main portal vein invasion (n = 6) and patients with an ECOG of > 2 were excluded (n = 1) with a final cohort of 34 patients.

RESULTS

Study population consisted of 34 patients, median age 62 years [60-71], tumor size 4.2 (2.8-7.4) cm, and 82% male. The median prescribed dose was 170 (126-200) Gy. The objective response rate at 6 months was 67% and disease control rate was 72%. The median survival was 18 months, median progression-free survival was 9.8 months. The 1- and 3-year survival rates were 76% and 57% in patients prescribed > 180 Gy, compared to 29% and 15% in patients with < 180 Gy (p = 0.01). Five of 15 Childs-Pugh A, ECOG < 1 patients (33%) were downstaged to resection, with complete pathologic necrosis in 40%, and 1 and 3-year survival rates of 100%. Grade-3 adverse events were seen in only 5/34 (15%), with no grade-4 or 5 adverse events.

CONCLUSION

Resin Y90-TARE using single compartment MIRD model for HCC with segmental and lobar vascular invasion can result in downstaging to resection in 33% of patients and higher prescribed doses (> 180 Gy) result in improved survival.

TACE vs. TARE for HCC ≥ 8 cm: A propensity score analysis

OBJECTIVE

This study aimed to compare transarterial chemoembolization (TACE) and transarterial radioembolization (TARE) as first-line treatments for unresectable HCC > 8 cm.

METHODS

This retrospective study analyzed 129 HCC patients with tumor diameters greater than 8 cm from January 2010 to December 2021, including 40 patients who received TARE, and 89 patients treated with TACE as primary treatment. Following Propensity Score Matching (PSM), 40 patients from each group were harmonized for baseline characteristics. Tumor responses were evaluated using mRECIST criteria, and survival outcomes were compared between treatment groups using Kaplan-Meier curves and the Log-rank test.

RESULTS

There was no significant difference in the objective response rate (ORR) and disease control rate (DCR) at 3, 6, and 12 months between the two groups; ORR and DCR were 72.6%, 83.1% in TACE group vs. 72.5%. 87.5% in TARE group for best tumor response (p-values: 0.625 and 0.981, respectively). Overall survival (OS) and progression-free survival (PFS) between the two groups were comparable pre- and post-PSM. After PSM, the OS was 33.2 months (20.0-58.6) in TACE group and 38.1 months (13.8-98.1) in TARE group (p = 0.53), while PFS was 11.5 months (7.7-18.4) and 9.1 months (5.2-23.8) respectively. After PSM, post-embolization syndrome developed more in TACE group (100% vs. 75%, p = 0.002). Major adverse events were 72% in TACE group vs. 5% in TARE group (p < 0.001).

CONCLUSIONS

TARE and TACE offer comparable efficacy in managing large HCC, with TARE providing a safer profile, suggesting its consideration as a preferable initial therapeutic approach for unresectable HCC patients with tumors larger than 8 cm.

Discordance between 90Y-PET/CT(MR)-estimated activity and dose calibrator measured administered activity: an international study in SIRT patients treated with resin and glass microspheres

PURPOSE

Therapeutic administration of 90Y-loaded microspheres is routinely used for primary and secondary liver tumours. For activity-based therapeutic prescription the activity must be within 10% of the intended activity. Previous studies reported significant discrepancies between manufacturer-declared vial activities and both experimental and Monte-Carlo assessments, greater than 10%, for resin/glass 90Y-microspheres. The objective of this work was to investigate whether these discrepancies were also seen in patients.

METHODS

We analysed patient 90Y-PET reconstructions (99 glass and 15 resin microspheres) from 4 different institutions and 4 different systems. We considered tail-fitting background scaling (TFBS) and absolute scaling (ABS), for scatter correction. Residuals after therapeutic injection were measured. Eighty-one patients were imaged with PET/CT and 33 with PET/MR. The PET measured activity (APET) was assessed in the whole liver. The ratio APET/Acalibrator was calculated for each patient, where Acalibrator was the injected activity measured by the dose calibrator corrected for residual and lung shunt.

RESULTS

Quantification ratio between calibrators and PET was significantly different from 1, regardless of the scatter correction used. In glass microspheres, the mean APET/CT/Acalibrator was 0.84 ± 0.06 for TFBS and 0.90 ± 0.06 for ABS (0.66 ± 0.09 and 0.76 ± 0.07 for (APET/MR/Acalibrator)). The mean APET/CT/Acalibrator ratio for resin microspheres was 1.16 ± 0.09 for TFBS and 1.30 ± 0.12 for ABS.

CONCLUSIONS

We observed in patients similar activity discrepancies as reported for vials, with a relative difference of 44 ± 16% between glass and resin 90Y-loaded microspheres. In 90Y hepatic radioembolization, the 10% accuracy prerequisite on knowing the administered therapeutic activity is then unlikely to be met.

Radiation Pneumonitis after Yttrium-90 Radioembolization: A Systematic Review

PURPOSE

To evaluate the available evidence of lung dosimetry and radiation pneumonitis (RP).

MATERIALS AND METHODS

The guideline regarding the maximum tolerated lung dose for yttrium-90 (90Y) radioembolization is an expert opinion (Level 5 evidence) based on a case series of 5 patients and recommends keeping the absorbed radiation dose to the lungs below 30 Gy per treatment and 50 Gy in a lifetime to prevent RP. The current understanding of the risks of RP is minimal despite its debilitating nature and high mortality rate. A systematic literature review was conducted in PubMed, Embase, Cochrane database, and Google Scholar for reported cases of RP. A database of 48 RP cases was compiled and analyzed.

RESULTS

Thirty patients were treated with resin and 16 patients with glass 90Y microspheres. The treatment device was not reported in 2 cases. RP developed a median of 3 months after radioembolization. The mortality rate was 40%. The hepatopulmonary shunt was not significantly different between the glass and the resin groups (21.2% [SD ± 14%] vs 15.6% [SD ± 7.5%]; P = .24). The radiation dose to the lungs was significantly higher in patients treated with glass compared with those with resin 90Y microspheres (41.4 Gy [SD ± 18.4] vs 21.5 Gy [SD ± 9.9]; P = .003).

CONCLUSIONS

The dose toxicity threshold for resin microspheres is lower than that of glass microspheres. The established 30-Gy dose limit may not be uniformly applicable in all cases and for both devices. The maximum tolerable lung doses should be reevaluated, and the shortcomings of the hepatopulmonary shunt calculation need to be corrected.

EASL Clinical Practice Guidelines on the management of hepatocellular carcinoma

Liver cancer is the third leading cause of cancer-related deaths worldwide, with hepatocellular carcinoma (HCC) accounting for approximately 90% of primary liver cancers. Advances in diagnostic and therapeutic tools, along with improved understanding of their application, are transforming patient treatment. Integrating these innovations into clinical practice presents challenges and necessitates guidance. These clinical practice guidelines offer updated advice for managing patients with HCC and provide a comprehensive review of pertinent data. Key updates from the 2018 EASL guidelines include personalised surveillance based on individual risk assessment and the use of new tools, standardisation of liver imaging procedures and diagnostic criteria, use of minimally invasive surgery in complex cases together with updates on the integrated role of liver transplantation, transitions between surgical, locoregional, and systemic therapies, the role of radiation therapies, and the use of combination immunotherapies at various stages of disease. Above all, there is an absolute need for a multiparametric assessment of individual risks and benefits, considering the patient's perspective, by a multidisciplinary team encompassing various specialties.

A bibliometric analysis of 30 years of research on transarterial radioembolization (TARE) for hepatocellular carcinoma

Introduction

Patients with advanced hepatocellular carcinoma (HCC) have very limited treatment options, among which transarterial radioembolization (TARE) receives increasing attention, relying on its promising efficacy and fewer side effect. However, a bibliometric analysis of TARE for HCC is still lacking. This study employed bibliometric methods to analyze the related articles over the past three decades, and aimed to identify trends in clinical research comparing TARE to other treatments.

Methods

Articles related with TARE for HCC were obtained from the Web of Science (WoS). After screening, the R package Bibliometrix was employed to explore the primary bibliometric characteristics. The number of publications was analyzed and mathematically fitted to a curve using Microsoft Excel 2021 and SPSS 25, and then was plotted in the graph using GraphPad Prism 8.0. VOSviewer, SCImago Graphica, and Pajek were utilized for the analysis of researchers' co-authorship, co-occurrence, and visualization. Keywords citation burst was detected by CiteSpace software.

Results

A total of 1,110 articles from 1993 to 2023 were included in our final analysis, among which the United States not only ranked the first in term of the number of published articles, also was at the forefront in other important indicators, including the total number of article citations and the average citation frequency. Riad Salem from Northwestern University, also being the organization with the greatest number of research papers, was the most active author and has published 96 papers. The keywords were classified into three clusters: 90Y microspheres for TARE, Basic research on TARE, and Clinical trial of TARE for HCC. Furthermore, we identified the most frequently cited keywords with strong citation bursts since 2020 were "multicenter," "overall survival" and "PET/CT."

Conclusion

Our study employed a bibliometric approach to achieve the visualization research on TARE for HCC, and further revealed the trends and frontiers of TARE research, providing valuable information for researchers to identify the critical and persistent challenges and select potential partners in related area. Based on our analysis, future research focus include the clinical comparative studies on the effect of TARE and TACE combined with immunotherapies or targeted therapy, dosimetry, and personalized TARE therapy for HCC.

Streamlining Radioembolization without Lung Shunt Estimation versus Regular Radioembolization in Patients with Hepatocellular Carcinoma within the Milan Criteria

PURPOSE

To assess the effectiveness and safety of streamlining transarterial radioembolization (S-TARE) without lung shunt fraction estimation using nuclear medicine imaging, compared with regular transarterial radioembolization (R-TARE), for patients with hepatocellular carcinoma (HCC) within the Milan criteria.

MATERIALS AND METHODS

Between January 2012 and December 2022, 100 consecutive patients with HCC within the Milan criteria underwent R-TARE (n = 38) or S-TARE (n = 62) and were retrospectively analyzed. Adverse events, complete response (CR) rates, and time to progression (TTP) by the modified Response Evaluation Criteria in Solid Tumours (mRECIST) and localized mRECIST following each treatment were compared using the Fisher exact test and Kaplan-Meier curve analyses with covariate adjustment.

RESULTS

Serious adverse events ≥ Grade 3 occurred in 3 (7.9%, 3/38) and 2 (3.2%, 2/62) patients following R-TARE and S-TARE, respectively (P = .365). No patients developed radiation pneumonitis. Among the 84 patients treated with glass microspheres, the CR rates were not significantly different after R-TARE (96.9%, 31/32) and S-TARE (90.4%, 47/52) (P = .400). There was no significant difference in TTP by mRECIST between R-TARE and S-TARE (unadjusted P = .400, adjusted P = .712). For patients with a single HCC, no significant difference was observed in TTP by localized mRECIST (unadjusted P = .090, adjusted P = .242). In the 16 patients treated with resin microspheres, the CR rates were 66.7% (4/6) for R-TARE and 90% (9/10) for S-TARE, respectively (P = .518).

CONCLUSIONS

S-TARE using yttrium-90 glass or resin microspheres was as effective and safe as R-TARE for HCC within the Milan criteria.

Do we need dosimetry for the optimization of theranostics in CNS tumors?

Radiopharmaceutical theranostic treatments have grown exponentially worldwide, and internal dosimetry has attracted attention and resources. Despite some similarities with chemotherapy, radiopharmaceutical treatments are essentially radiotherapy treatments, as the release of radiation into tissues is the determinant of the observed clinical effects. Therefore, absorbed dose calculations are key to explaining dose-effect correlations and individualizing radiopharmaceutical treatments. The present article introduces the basic principles of internal dosimetry and provides an overview of available loco-regional and systemic radiopharmaceutical treatments for central nervous system (CNS) tumors. The specific characteristics of dosimetry as applied to these treatments are highlighted, along with their limitations and most relevant results. Dosimetry is performed with higher precision and better reproducibility than in the past, and dosimetric data should be systematically collected, as treatment planning and verification may help exploit the full potential of theranostic of CNS tumors.

An Evaluation of 90Y Bremsstrahlung SPECT Image Quality in the Presence of 99mTc: A Technical Perspective on Same-Day Radioembolization

In same-day radioembolization, 99mTc-MAA SPECT/CT, 90Y radioembolization, and post-treatment 90Y SPECT/CT procedures are conducted on the same-day, resulting in a dual-isotope environment of 90Y and 99mTc during post-treatment imaging. This study aimed to quantify the impact of 99mTc on 90Y bremsstrahlung-SPECT/CT image quality and to establish an optimised imaging protocol for both clinical practice, and with advanced reconstruction techniques. Utilising a NEMA IQ phantom, contrast recovery coefficients (CRCs) were measured to evaluate the 90Y image quality degradation caused by 99mTc. SPECT/CT scans of 90Y-only and 90Y with varying amounts of 99mTc were conducted using a standard protocol (90-120 keV energy window, high-energy collimator) and various dual-isotope protocols. The standard protocol resulted in a marked CRC reduction, with the largest sphere's CRC decreasing from 0.21 (90Y-only) to 0.05 when 99mTc activity was 5% of 90Y. For an optimised protocol (160-200 keV energy window, high-energy collimator) CRC values were 0.16 for 90Y-only and 0.15 for 90Y+99mTc. The highest CRC values were achieved with an advanced Monte Carlo-based reconstruction, showing 0.58 for 90Y-only and 0.46 for 90Y+99mTc. Image quality degradation was noted in dual-isotope settings even when using an optimised protocol. Advanced reconstruction techniques markedly improved post-treatment image quality.

The role of biomarkers and dosimetry parameters in overall and progression free survival prediction for patients treated with personalized 90Y glass microspheres SIRT: a preliminary machine learning study

BACKGROUND

Overall Survival (OS) and Progression-Free Survival (PFS) analyses are crucial metrics for evaluating the efficacy and impact of treatment. This study evaluated the role of clinical biomarkers and dosimetry parameters on survival outcomes of patients undergoing 90Y selective internal radiation therapy (SIRT).

MATERIALS/METHODS

This preliminary and retrospective analysis included 17 patients with hepatocellular carcinoma (HCC) treated with 90Y SIRT. The patients underwent personalized treatment planning and voxel-wise dosimetry. After the procedure, the OS and PFS were evaluated. Three structures were delineated including tumoral liver (TL), normal perfused liver (NPL), and whole normal liver (WNL). 289 dose-volume constraints (DVCs) were extracted from dose-volume histograms of physical and biological effective dose (BED) maps calculated on 99mTc-MAA and 90Y SPECT/CT images. Subsequently, the DVCs and 16 clinical biomarkers were used as features for univariate and multivariate analysis. Cox proportional hazard ratio (HR) was employed for univariate analysis. HR and the concordance index (C-Index) were calculated for each feature. Using eight different strategies, a cross-combination of various models and feature selection (FS) methods was applied for multivariate analysis. The performance of each model was assessed using an averaged C-Index on a three-fold nested cross-validation framework. The Kaplan-Meier (KM) curve was employed for univariate and machine learning (ML) model performance assessment.

RESULTS

The median OS was 11 months [95% CI: 8.5, 13.09], whereas the PFS was seven months [95% CI: 5.6, 10.98]. Univariate analysis demonstrated the presence of Ascites (HR: 9.2[1.8,47]) and the aim of SIRT (segmentectomy, lobectomy, palliative) (HR: 0.066 [0.0057, 0.78]), Aspartate aminotransferase (AST) level (HR:0.1 [0.012-0.86]), and MAA-Dose-V205(%)-TL (HR:8.5[1,72]) as predictors for OS. 90Y-derived parameters were associated with PFS but not with OS. MAA-Dose-V205(%)-WNL, MAA-BED-V400(%)-WNL with (HR:13 [1.5-120]) and 90Y-Dose-mean-TL, 90Y-D50-TL-Gy, 90Y-Dose-V205(%)-TL, 90Y-Dose- D50-TL-Gy, and 90Y-BED-V400(%)-TL (HR:15 [1.8-120]) were highly associated with PFS among dosimetry parameters. The highest C-index observed in multivariate analysis using ML was 0.94 ± 0.13 obtained from Variable Hunting-variable-importance (VH.VIMP) FS and Cox Proportional Hazard model predicting OS, using clinical features. However, the combination of VH. VIMP FS method with a Generalized Linear Model Network model predicting OS using Therapy strategy features outperformed the other models in terms of both C-index and stratification of KM curves (C-Index: 0.93 ± 0.14 and log-rank p-value of 0.023 for KM curve stratification).

CONCLUSION

This preliminary study confirmed the role played by baseline clinical biomarkers and dosimetry parameters in predicting the treatment outcome, paving the way for the establishment of a dose-effect relationship. In addition, the feasibility of using ML along with these features was demonstrated as a helpful tool in the clinical management of patients, both prior to and following 90Y-SIRT.

New frontiers in radioembolization

Radioembolization is a locoregional transarterial therapy that combines radionuclide and micron-sized beads to deliver radiation internally to the target tumors based on the arterial blood flow. While initially developed as a palliative treatment option, radioembolization is now used for curative intent treatment, neoadjuvant therapy, and method to downstage or bridge for liver transplant. Radioembolization has become increasingly utilized and is an important therapeutic option for the management of hepatocellular carcinoma and liver metastasis. This article provides an overview of the techniques, challenges, and novel developments in radioembolization, including new dosimetry techniques, radionuclides, and new target tumors.

90Y SIR-Spheres Activity Measurement with New SIROS D-Vial Delivery Kit

A new 90Y SIR-Spheres delivery kit (SIROS D-vial and shield) has been introduced with a different physical form from the legacy V-Vial kit. Here, we establish the dose calibrator settings and exposure-rate-to-activity conversion factor to assay 90Y SIR-Spheres activity in the new SIROS kit. Methods: Eight D-vials with initial 90Y activities from 1.2 to 6.6 GBq within acrylic shields were assayed with dose calibrators and exposure-rate meters until activities decayed to approximately 0.1 GBq. The dose calibrator settings resulting in the lowest median activity errors and the best-fit slope of exposure rate versus activity were identified. Results: SIROS D-vial 90Y activity can be accurately and reliably estimated directly using setting 51 × 10 on both the CRC-15R and the CRC-55tR dose calibrators (errors within ±0.5%) and indirectly with an exposure-rate reading at 30 cm using conversion factor 0.664 ± 0.003 GBq/(mR/h) (R 2 = 0.985). Conclusion: Dose calibrator settings and exposure-rate-to-activity conversion factor for 90Y activity assays with new SIROS kit should be updated from legacy V-Vial parameters to avoid an approximately 10% underestimation.

Measure of 90Y-glass microspheres residue post-TARE using PET/CT and potential impact on tumor absorbed dose in comparison 99mTc-MAA SPECT/CT dosimetry

BACKGROUND

Transarterial radio-embolization (TARE) became a routine procedure for non-resectable liver tumor mainly hepatocellular carcinoma (HCC). Personalized dosimetry to the index lesion increased tumor response rate. However, there is no requirement to measure the precise activity injected during TARE. We measured 90Y-glass microspheres residue (90Y-Res) in the application system after TARE and assessed its potential impact on the tumor absorbed dose (AD) previously planned with 99mTc MAA SPECT/CT.

METHODS

We measured 90Y-Res using PET/CT in all patients that underwent TARE using 90Y-glass-microspheres for non-resectable liver tumors over one year.

RESULTS

90Y-Res was measured in 34 patients (HCC n = 22) with 61 injections, 93.1 ± 94.6 MBq [2-437] that was 4.8 ± 3.5% [0.2-13.7] in comparison to the activity measured in the sealed TheraSphere™ vial (ρ = 0.697; p < 0.001).

CONCLUSION

We reported an average of 5% 90Y-Res using PET/CT after TARE with the strongest association to the activity in the TheraSphere™ vial. Therefore, when a high 90Y-Res is suspected on the survey meter, a 90Y-PET/CT scan of 90Y-Res might be useful as a first step to estimate if the target lesion received the recommended AD, especially in HCC patients with borderline tumor dosimetry on the pre-treatment 99mTc-MAA SPECT/CT.

Prognostic factors influencing outcomes in hepatocellular carcinoma patients undergoing selective internal radiation therapy

Selective internal radiation therapy (SIRT) has emerged as a viable endovascular treatment strategy for hepatocellular carcinoma (HCC). According to the Barcelona Clinic Liver Cancer (BCLC) classification, SIRT is currently recommended for early- and intermediate-stage HCC that is unsuitable for alternative locoregional therapies. Additionally, SIRT remains a recommended treatment for patients with advanced-stage HCC and portal vein thrombosis (PVT) without extrahepatic metastasis. Several studies have shown that SIRT is a versatile and promising treatment with a wide range of applications. Consequently, given its favourable characteristics in various scenarios, SIRT could be an encouraging treatment option for patients with HCC across different BCLC stages. Over the past decade, an increasing number of studies have focused on better understanding the prognostic factors associated with SIRT to identify patients who derive the most benefit from this treatment or to refine the optimal technical procedures of SIRT. Several variables can influence treatment decisions, with a growing emphasis on a personalised approach. This review, based on the literature, will focus on the prognostic factors associated with the effectiveness of radioembolization and related complications. By comprehensively analysing these factors, we aimed to provide a clearer understanding of how to optimise the use of SIRT in managing HCC patients, thereby enhancing outcomes across various clinical scenarios.

Paraneoplastic Diarrhea From Medullary Thyroid Carcinoma Resolved With Yttrium-90 Radioembolization of Liver Metastases

Medullary thyroid carcinoma (MTC) can often have an indolent course despite distant metastatic disease. Additionally, given that metastatic MTC is incurable and systemic therapies have non-negligeable toxicities, localized treatments are often favored in presence of oligo-progressive disease. Transarterial radioembolization (TARE) with yttrium-90 (Y90) has emerged as a safe and efficacious treatment for nonresectable primary and metastatic liver tumors, yet data supporting its use in metastatic MTC are limited. We present the case of a patient with hereditary MTC and large bilobar liver metastases who demonstrated tumor response and resolution of their paraneoplastic diarrhea following TARE with Y90 microspheres.

Clinical Results of Holmium-166 Radioembolization with Personalized Dosimetry for the Treatment of Hepatocellular Carcinoma

Transarterial radioembolization (TARE) with 166Ho-loaded microspheres is an established locoregional treatment for hepatocellular carcinoma (HCC), introduced in 2010. This study evaluates the clinical outcome of patients with HCC who underwent 166Ho-TARE with personalized dosimetry. Twenty-seven patients with 36 TARE procedures were analyzed. Treatment planning, execution, and evaluation was possible without complications in all cases. At the 3-month follow-up, disease control in the treated liver was achieved in 81.8% of patients (complete remission, partial remission, and stable disease in 36.4%, 31.8%, and 13.6%, respectively). The median overall survival (OS) was 17.2 months, and progression-free survival (PFS) in the treated liver was 11 months. Statistically significant positive correlations were observed between the achieved radiation dose for the tumor and both PFS (r = 0.62, p < 0.05) and OS (r = 0.48, p < 0.05), suggesting a direct dose-response relationship. The calculated achieved dose was 8.25 Gy lower than the planned dose, with relevant variance between planned and achieved doses in individual cases. These results confirm the efficacy of the 166Ho-TARE holmium platform and underscore the potential of voxel-based, personalized dosimetry to improve clinical outcomes.

Use of dose-volume histograms for metabolic response prediction in hepatocellular carcinoma patients undergoing transarterial radioembolization with Y-90 resin microspheres

INTRODUCTION

Voxel-based dosimetry offers improved outcomes in the treatment of hepatocellular carcinoma (HCC) with transarterial radioembolization (TARE) using glass microspheres. However, the adaptation of voxel-based dosimetry to resin-based microspheres has been poorly studied, and the prognostic relevance of heterogeneous dose distribution remains unclear. This study aims to explore the use of dose-volume histograms for resin microspheres and to determine thresholds for objective metabolic response in HCC patients treated with resin-based TARE.

METHODS

We retrospectively reviewed HCC patients who underwent TARE with Y-90-loaded resin microspheres in our institution between January 2021 and December 2022. Voxel-based dosimetry was performed on post-treatment Y-90 PET/CT images to extract parameters including mean dose absorbed by the tumor (mTD), the percentage of the targeted tumor volume (pTV), and the minimum doses absorbed by consecutive percentages within the tumor volume (D10, D25, D50, D75, D90). Assessment of metabolic response was done according to PERCIST criteria with F-18 FDG PET/CT imaging at 8-12 weeks after the treatment.

RESULTS

This study included 35 lesions targeted with 22 TARE sessions in 19 patients (15 males, 4 females, mean age 60 ± 13 years). Objective metabolic response was achieved in 43% of the lesions (n = 15). Responsive lesions had significantly higher mTD, pTV, and D25-D90 values (all p < 0.05). Optimal cut-off values for mTD, pTV, and D50 were 94.6 Gy (sensitivity 73%, specificity 70%, AUC 0.72), 94% (sensitivity 73%, specificity 55%, AUC 0.64), and 91 Gy (sensitivity 80%, specificity 80%, AUC 0.80), respectively.

CONCLUSION

Parameters derived from dose-volume histograms could offer valuable insights for predicting objective metabolic response in HCC patients treated with resin-based TARE. If verified with larger prospective cohorts, these parameters could enhance the precision of dose distribution and potentially optimize treatment outcomes.

Outcomes in Patients with Macrotrabecular-Massive Subtype Hepatocellular Carcinoma Treated with Yttrium-90 Transarterial Radioembolization

PURPOSE

To compare the outcomes of yttrium-90 transarterial radioembolization (TARE) in patients with hepatocellular carcinoma (HCC) with and without macrotrabecular-massive (MTM) subtypes.

MATERIALS AND METHODS

Forty-one consecutive patients with HCC (male, 90.3%; mean age, 65.3 years [SD ± 10.7]) who underwent yttrium-90 TARE between September 2014 and January 2022 were grouped into the MTM-HCC (n = 17, 41.5%) and non-MTM-HCC (n = 24, 58.5%) groups based on their histopathological subtypes. Demographic, clinical, and radiological characteristics were compared. Survival, univariate, and multivariate analyses were performed, and prognostic factors were evaluated.

RESULTS

In MTM-HCC group, the rates of moderately to poorly differentiated tumors were significantly higher (13/17 vs 8/16, P = .007), and new intrahepatic/extrahepatic metastases were detected more frequently (12/17 vs 15/24, P = .038). Median overall survival (OS) in the cohort was 29 months (range, 17.1-40.9 months), whereas patients with MTM-HCC had a significantly shorter median OS (20 vs 44 months, P = .014). In univariate analysis, MTM-HCC subtype (hazard ratio [HR], 2.690; P = .021), the presence of satellite nodules (HR, 3.810; P = .004), and macrovascular invasion (HR, 3.321; P = .012) were identified as significant prognostic factors. In multivariate analysis, MTM-HCC subtype and macrovascular invasion were determined as independent poor prognostic factors (P = .038 and P = .012, respectively).

CONCLUSIONS

In patients with HCC treated with yttrium-90 TARE, both the rates of moderately to poorly differentiated histopathological classes and the development of intrahepatic or extrahepatic metastases were significantly higher in the MTM-HCC subtype. OS was worse in patients with MTM-HCC, and macrovascular invasion and MTM-HCC subtype were identified as independent poor prognostic factors.

Are survival outcomes dependent on the tumour dose threshold of 139 Gy in patients with chemorefractory metastatic colorectal cancer treated with yttrium-90 radioembolization using glass particles? A real-world single-centre study

OBJECTIVES

To compare the survival and objective response rate (ORR) of the patients receiving estimated tumour absorbed dose (ETAD) <140 Gy versus ETAD ≥140 Gy in patients with advanced chemorefractory colorectal carcinoma liver metastases (CRCLM) treated with yttrium-90 transarterial radioembolization (90Y TARE).

METHODS

Between August 2016 and August 2023 adult patients with unresectable, chemorefractory CRCLM treated with 90Y TARE using glass particles, were retrospectively enrolled. Primary outcomes were overall survival (OS) and hepatic progression free survival (hPFS). Secondary outcome was ORR.

RESULTS

A total of 40 patients with a mean age of 66.2 ± 7.8 years met the inclusion criteria. Mean ETAD for group 1 (ETAD <140 Gy) and group 2 (ETAD ≥140) were 131.2 ± 17.4 Gy versus 195 ± 45.6 Gy, respectively. The mean OS and hPFS for group 1 versus group 2 were 12 ± 10.3 months and 8.1 ± 9.3 months versus 9.3 ± 3 months and 7.1 ± 8.4 months, respectively and there were no significant differences (P = .181 and P = .366, respectively). ORR did not show significant difference between the groups (P = .432).

CONCLUSION

In real-world practice, no significant difference was found in OS, hPFS, and ORR between patients who received ETAD <140 Gy versus ETAD ≥140 Gy in patients with CRCLM, in this series.

ADVANCES IN KNOWLEDGE

This study demonstrated that increased tumour absorbed doses in radioembolization may not provide additional significant advantage for OS and hPFS for patients with CRCLM.

A microscopic model of the dose distribution in hepatocellular carcinoma after selective internal radiation therapy

The dosimetry evaluation for the selective internal radiation therapy is currently performed assuming a uniform activity distribution, which is in contrast with literature findings. A 2D microscopic model of the perfused liver was developed to evaluate the effect of two different 90Y microspheres distributions: i) homogeneous partitioning with the microspheres equally distributed in the perfused liver, and ii) tumor-clustered partitioning where the microspheres distribution is inferred from the patient specific images.

METHODS

Two subjects diagnosed with liver cancer were included in this study. For each subject, abdominal CT scans acquired prior to the SIRT and post-treatment 90Y positron emission tomography were considered. Two microspheres partitionings were simulated namely homogeneous and tumor-clustered partitioning. The homogeneous and tumor-clustered partitionings were derived starting from CT images. The microspheres radiation is simulated by means of Russell's law.

RESULTS

In homogenous simulations, the dose delivery is uniform in the whole liver while in the tumor-clustered simulations a heterogeneous distribution of the delivered dose is visible with higher values in the tumor regions. In addition, in the tumor-clustered simulation, the delivered dose is higher in the viable tumor than in the necrotic tumor, for all patients. In the tumor-clustered case, the dose delivered in the non-tumoral tissue (NTT) was considerably lower than in the perfused liver.

CONCLUSIONS

The model proposed here represents a proof-of-concept for personalized dosimetry assessment based on preoperative CT images.

Characterizing the voxel-based approaches in radioembolization dosimetry with reDoseMC

BACKGROUND

Yttrium-90 (90 Y $^{90}{\rm {Y}}$ ) represents the primary radioisotope used in radioembolization procedures, while holmium-166 (166 Ho $^{166}{\rm {Ho}}$ ) is hypothesized to serve as a viable substitute for90 Y $^{90}{\rm {Y}}$ due to its comparable therapeutic potential and improved quantitative imaging. Voxel-based dosimetry for these radioisotopes relies on activity images obtained through PET or SPECT and dosimetry methods, including the voxel S-value (VSV) and the local deposition method (LDM). However, the evaluation of the accuracy of absorbed dose calculations has been limited by the use of non-ideal reference standards and investigations restricted to the liver. The objective of this study was to expand upon these dosimetry characterizations by investigating the impact of image resolutions, voxel sizes, target volumes, and tissue materials on the accuracy of90 Y $^{90}{\rm {Y}}$ and166 Ho $^{166}{\rm {Ho}}$ dosimetry techniques.

METHODS

A specialized radiopharmaceutical dosimetry software called reDoseMC was developed using the Geant4 Monte Carlo toolkit and validated by benchmarking the generated90 Y $^{90}{\rm {Y}}$ kernels with published data. The decay spectra of both90 Y $^{90}{\rm {Y}}$ and166 Ho $^{166}{\rm {Ho}}$ were also compared. Multiple VSV kernels were generated for the liver, lungs, soft tissue, and bone for isotropic voxel sizes of 1 mm, 2 mm, and 4 mm. Three theoretical phantom setups were created with 20 or 40 mm activity and mass density inserts for the same three voxel sizes. To replicate the limited spatial resolutions present in PET and SPECT images, image resolutions were modeled using a 3D Gaussian kernel with a Full Width at Half Maximum (FWHM) ranging from 0 to 16 mm and with no added noise. The VSV and LDM dosimetry methods were evaluated by characterizing their respective kernels and analyzing their absorbed dose estimates calculated on theoretical phantoms. The ground truth for these estimations was calculated using reDoseMC.

RESULTS

The decay spectra obtained through reDoseMC showed less than a 1% difference when compared to previously published experimental data for energies below 1.9 MeV in the case of90 Y $^{90}{\rm {Y}}$ and less than 1% for energies below 1.5 MeV for166 Ho $^{166}{\rm {Ho}}$ . Additionally, the validation kernels for90 Y $^{90}{\rm {Y}}$ VSV exhibited results similar to those found in published Monte Carlo codes, with source dose depositions having less than a 3% error margin. Resolution thresholds (FWHM thresh s ${\rm {FWHM}}_\mathrm{thresh}{\rm {s}}$ ), defined as resolutions that resulted in similar dose estimates between the LDM and VSV methods, were observed for90 Y $^{90}{\rm {Y}}$ . They were 1.5 mm for bone, 2.5 mm for soft tissue and liver, and 8.5 mm for lungs. For166 Ho $^{166}{\rm {Ho}}$ , the accuracy of absorbed dose deposition was found to be dependent on the contributions of absorbed dose from photons. Volume errors due to variations in voxel size impacted the final dose estimates. Larger target volumes yielded more accurate mean doses than smaller volumes. For both radioisotopes, the radial dose profiles for the VSV and LDM approximated but never matched the reference standard.

CONCLUSIONS

reDoseMC was developed and validated for radiopharmaceutical dosimetry. The accuracy of voxel-based dosimetry was found to vary widely with changes in image resolutions, voxel sizes, chosen target volumes, and tissue material; hence, the standardization of dosimetry protocols was found to be of great importance for comparable dosimetry analysis.

Toxicity comparison of yttrium-90 resin and glass microspheres radioembolization

BACKGROUND

To investigate the clinical, hematological and biochemical toxicity differences between glass and resin yttrium-90 (90Y)-microspheres radioembolization treatment of primary and metastatic liver disease.

METHODS

Between May 2014 and November 2016 all consecutive glass and resin 90Y microspheres radioembolization treatments were retrospectively analyzed. Biochemical, hematological and clinical data were collected at treatment day, two weeks, one month and three months follow-up. Post-treatment 90Y PET/CTs were assessed for the absorbed doses in non-tumorous liver volume (DNTLV) and tumor volume (DTV). Biochemical, hematological and clinical toxicity were compared between glass and resin using chi square tests and repeated ANOVA measures. Biochemical and clinical toxicity was correlated with DNTLV,total by means of Pearson correlation and independent t-tests.

RESULTS

A total of 85 patients were included (N.=44 glass, N.=41 resin). Clinical toxicity the day after treatment (i.e. abdominal pain [P=0.000], nausea [P=0.000] and vomiting [P=0.003]) was more prevalent for resin. Biochemical and hematological toxicities were similar for both microspheres. The DNTLV,total was significantly higher in patients with REILD grade ≥3 in the resin group (43.5 versus 33.3 Gy [P=0.050]). A similar non-significant trend was seen in the glass group: 95.0 versus 69.0 Gy [P=0.144].

CONCLUSIONS

The clinical, hematological and biochemical toxicity of radioembolization treatment with glass and resin is comparable, however, post-embolization syndrome related complaints are more common for resin.

Efficacy and Safety of Radiation Segmentectomy with 90Y Resin Microspheres for Hepatocellular Carcinoma

Background Limited data are available on radiation segmentectomy (RS) for treatment of hepatocellular carcinoma (HCC) using yttrium 90 (90Y) resin microsphere doses determined by using a single-compartment medical internal radiation dosimetry (MIRD) model. Purpose To evaluate the efficacy and safety of RS treatment of HCC with 90Y resin microspheres using a single-compartment MIRD model and correlate posttreatment dose with outcomes. Materials and Methods This retrospective single-center study included adult patients with HCC who underwent RS with 90Y resin microspheres between July 2014 and December 2022. Posttreatment PET/CT and dosimetry were performed. Adverse events were assessed using the Common Terminology Criteria for Adverse Events, version 5.0. Per-lesion and overall response rates (ie, complete response [CR], objective response, disease control, and duration of response) were assessed at imaging using the Modified Response Evaluation Criteria in Solid Tumors, and overall survival (OS) was assessed using Kaplan-Meier analysis. Results Among 67 patients (median age, 69 years [IQR, 63-78 years]; 54 male patients) with HCC, median tumor absorbed dose was 232 Gy (IQR, 163-405 Gy). At 3 months, per-lesion and overall (per-patient) CR was achieved in 47 (70%) and 41 (61%) of 67 patients, respectively. At 6 months (n = 46), per-lesion rates of objective response and disease control were both 94%, and per-patient rates were both 78%. A total of 88% (95% CI: 79 99) and 72% (95% CI: 58, 90) of patients had a per-lesion and overall duration of response of 1 year or greater. At 1 month, a grade 3 clinical adverse event (abdominal pain) occurred in one of 67 (1.5%) patients. Median posttreatment OS was 26 months (95% CI: 20, not reached). Disease progression at 2 years was lower in the group that received 300 Gy or more than in the group that received less than 300 Gy (17% vs 61%; P = .047), with no local progression in the former group through the end of follow-up. Conclusion Among patients with HCC who underwent RS with 90Y resin microspheres, 88% and 72% achieved a per-lesion and overall duration of response of 1 year or greater, respectively, with one grade 3 adverse event. In patients whose tumors received 300 Gy or more according to posttreatment dosimetry, a disease progression benefit was noted. © RSNA, 2024 Supplemental material is available for this article.

Role of Flex-Dose Delivery Program in Patients Affected by HCC: Advantages in Management of Tare in Our Experience

Background: Introduced in the latest BCLC 2022, endovascular trans-arterial radioembolization (TARE) has an important role in the treatment of unresectable hepatocellular carcinoma (HCC) as a "bridge" or "downstaging" of disease. The evolution of TARE technology allows a more flexible and personalized target treatment, based on the anatomy and vascular characteristics of each HCC. The flex-dose delivery program is part of this perspective, which allows us to adjust the dose and its radio-embolizing power in relation to the size and type of cancer and to split the therapeutic dose of Y90 in different injections (split-bolus). Methods: From January 2020 to January 2022, we enrolled 19 patients affected by unresectable HCC and candidates for TARE treatment. Thirteen patients completed the treatment following the flex-dose delivery program. Response to treatment was assessed using the mRECIST criteria with CT performed 6 and 9 months after treatment. Two patients did not complete the radiological follow-up and were not included in this retrospective study. The final cohort of this study counts eleven patients. Results: According to mRECIST criteria, six months of follow-up were reported: five cases of complete response (CR, 45.4% of cases), four cases of partial response (PR, 36.4%), and two cases of progression disease (PD, 18.2%). Nine months follow-up reported five cases of complete response (CR, 45.4%), two cases of partial response (PR, 18.2%), and four cases of progression disease (PD, 36.4%). No intra and post-operative complications were described. The average absorbed doses to the hepatic lesion and to the healthy liver tissue were 319 Gy (range 133-447 Gy) and 9.5 Gy (range 2-19 Gy), respectively. Conclusions: The flex-dose delivery program represents a therapeutic protocol capable of "saving" portions of healthy liver parenchyma by designing a "custom-made" treatment for the patient.

Recommendations for the management of yttrium-90 radioembolization in the treatment of patients with colorectal cancer liver metastases: a multidisciplinary review

PURPOSE

Strategies for the treatment of liver metastases from colon cancer (lmCRC) are constantly evolving. Radioembolization with yttrium 90 (Y-90 TARE) has made significant advancements in treating liver tumors and is now considered a potential option allowing for future resection. This study reviewed the scientific evidence and developed recommendations for using Y-90 TARE as a treatment strategy for patients with unresectable lmCRC.

METHODS

A multidisciplinary scientific committee, consisting of experts in medical oncology, hepatobiliary surgery, radiology, and nuclear medicine, all with extensive experience in treating patients with ImCRC with Y-90 TARE, led this project. The committee established the criteria for conducting a comprehensive literature review on Y-90 TARE in the treatment of lmCRC. The data extraction process involved addressing initial preliminary inquiries, which were consolidated into a final set of questions.

RESULTS

This review offers recommendations for treating patients with lmCRC using Y-90 TARE, addressing four areas covering ten common questions: 1) General issues (multidisciplinary tumor committee, indications for treatment, contraindications); 2) Previous process (predictive biomarkers for patient selection, preintervention tests, published evidence); 3) Procedure (standard procedure); and 4) Post-intervention follow-up (potential toxicity and its management, parameters for evaluation, quality of life).

CONCLUSIONS

Based on the insights of the multidisciplinary committee, this document offers a comprehensive overview of the technical aspects involved in the management of Y-90 TARE. It synthesizes recommendations for applying Y-90 TARE across various phases of the treatment process.

Factors Impacting Survival After Transarterial Radioembolization in Patients with Unresectable Intrahepatic Cholangiocarcinoma: A Combined Analysis of the Prospective CIRT Studies

PURPOSE

Transarterial radioembolization (TARE) with Yttrium-90 resin microspheres is a treatment option for patients with intrahepatic cholangiocarcinoma (ICC). However, optimising the timing of TARE in relation to systemic therapies and patient selection remains challenging. We report here on the effectiveness, safety, and prognostic factors associated with TARE for ICC in a combined analysis of the prospective observational CIRT studies (NCT02305459 and NCT03256994).

METHODS

A combined analysis of 174 unresectable ICC patients enrolled between 2015 and 2020 was performed. Patient characteristics and treatment-related data were collected at baseline; adverse events and time-to-event data (overall survival [OS], progression-free survival [PFS] and hepatic PFS) were collected at every follow-up visit. Log-rank tests and a multivariable Cox proportional hazard model were used to identify prognostic factors.

RESULTS

Patients receiving a first-line strategy of TARE in addition to any systemic treatment had a median OS and PFS of 32.5 months and 11.3 months. Patients selected for first-line TARE alone showed a median OS and PFS of 16.2 months and 7.4 months, whereas TARE as 2nd or further treatment-line resulted in a median OS and PFS of 12 and 9.3 months (p = 0.0028), and 5.1 and 3.5 months (p = 0.0012), respectively. Partition model dosimetry was an independent predictor for better OS (HR 0.59 [95% CI 0.37-0.94], p = 0.0259). No extrahepatic disease, no ascites, and < 6.1 months from diagnosis to treatment were independent predictors for longer PFS.

CONCLUSION

This combined analysis indicates that in unresectable ICC, TARE in combination with any systemic treatment is a promising treatment option.

LEVEL OF EVIDENCE

level 3, Prospective observational.

Comparison of absorbed doses to the tumoral and non-tumoral liver in HCC patients undergoing 99mTc-MAA and 90Y-microspheres radioembolization

PURPOSE

This study aimed to determine the absorbed doses in the tumoral-liver and non-tumoral liver of hepatocellular carcinoma (HCC) patients undergoing radioembolization with Yttrium-90 (90Y) resin microspheres, and compared with those derived from 99mTc-MAA using the partition model.

METHODS

A total of 42 HCC patients (28 males and 14 females, mean age 65 ± 11.51 years) who received 45 treatment sessions with 90Y-microspheres between 2016 and 2021 were included. Pre-treatment 99mTc-MAA and post-treatment 90Y-bremsstrahlung SPECT/CT were acquired for each patient. Semi-automated segmentation of regions of interest (ROIs) was performed using MIM Encore software to determine the tumor-liver ratio (TLR) encompassing the liver volume, tumoral-liver, and lungs, and verified by both nuclear medicine physician and interventional radiologist. A partition dosimetry model was used to estimate the administered activity of 90Y-microspheres and the absorbed doses to the tumoral-liver and non-tumoral liver. The student's paired t test and Bland-Altman plot were used for the statistical analysis.

RESULTS

The mean TLR values obtained from 99mTc-MAA SPECT/CT and 90Y-bremsstrahlung SPECT/CT were 4.78 ± 3.51 and 2.73 ± 1.18, respectively. The mean planning administered activity of 90Y-microspheres based on 99mTc-MAA SPECT/CT was 1.56 ± 0.80 GBq, while the implanted administered activity was 2.53 ± 1.23 GBq (p value < 0.001). The mean absorbed doses in the tumoral-liver estimated from 99mTc-MAA and 90Y-bremsstrahlung SPECT/CT were 127.44 ± 4.36 Gy and 135.98 ± 6.30 Gy, respectively. The corresponding mean absorbed doses in the non-tumoral liver were 34.61 ± 13.93 Gy and 55.04 ± 16.36 Gy.

CONCLUSION

This study provides evidence that the administered activity of 90Y-microspheres, as estimated from 90Y-bremsstrahlung SPECT/CT, was significantly higher than that estimated from 99mTc-MAA SPECT/CT resulted in increased absorbed doses in both the tumoral-liver and non-tumoral liver. However, 99mTc-MAA SPECT/CT remains a valuable planning tool for predicting the distribution of 90Y-microspheres in liver cancer treatment.

Technical Note: Impact of impurities on Yttrium-90 glass microsphere activity quantitation

BACKGROUND

Glass 90 Y microspheres are produced with known radionuclide impurities. These impurities are not independently monitored. Clinical instruments, including ionization chamber dose calibrators and positron emmission tomography (PET) cameras, can be much more sensitive in detecting signals from these impurities than to signals from 90 Y itself.

PURPOSE

The "typical" levels of 90 Y impurities have been studied to assess their impact on dosimetry during internal implantation, and for the management of waste. However, unaccounted-for decay spectra of impurities can also have an impact on dose calibrator and PET readings. Thus, even what might be considered negligibly small impurity fractions, can in principle cause substantial overestimates of the amount of 90 Y activity present in a sample. To our knowledge, quantitative effects of radionuclide impurities in glass microspheres on activity measurements have not been documented in the field. As activity quantitation for dosimetry and its correlations with outcome becomes more prevalent, the effects of impurities on measurements may remain unaccounted for in dosimetry studies.

METHODS

In this letter, we review theoretical and physical considerations that will result in asymmetric errors in quantitation from 90 Y impurities and estimate their typical and potential impact on clinical utilization. Among the common impurities 88 Y is of particular concern for its impact on 90 Y dose measurements because of its decay characteristics, along with other isotopes 91 Y and 46 Sc which can also impact measurements.

RESULTS

The typical level of 88 Y impurities reported by the manufacturer should only cause small errors in dose calibrator and PET measurements made within the 12-day label-specified use-by period, up to 2.0% and 1.6%, respectively. However, the product specification max allowable impurity levels, specified by the manufacturer, leave open the potential for much greater bias from within the 12-day use-by period, potentially as high as 13.2% for dose calibrator measurements and 10.6% for PET from the 88 Y impurities.

CONCLUSIONS

While typical levels of impurities appear to have acceptable impact on patient absorbed dose, it should be noted that they can have adverse effects on 90 Y radioactivity measurements. Furthermore, there is currently minimal independent verification and/or monitoring of impurity levels within the field.

Applications of Yttrium-90 (90Y) in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the most common primary liver cancer, affecting millions of people worldwide. Due to the lack of systemic radiation therapy in hepatocellular carcinoma, researchers have been investigating the use of yttrium-90 (90Y) radioembolization for local-regional tumor control since the 1960s. With the development of glass and resin 90Y microspheres and the durable local control, good long-term efficacy, and equivalent tumor responsiveness and tolerability of 90Y-selective internal irradiation compared with alternative therapies such as transarterial chemoembolization (TACE) and sorafenib, 90Y radioembolization has gradually been applied in the treatment of hepatocellular carcinoma of all stages. In this article, we summarize the latest progress of 90Y in the treatment of hepatocellular carcinoma in terms of its principle, advantages, indications, contraindications, efficacy and adverse effects.

Phantom study for 90Y liver radioembolization dosimetry with a long axial field-of-view PET/CT

PURPOSE

The physical properties of yttrium-90 (90Y) allow for imaging with positron emission tomography/computed tomography (PET/CT). The increased sensitivity of long axial field-of-view (LAFOV) PET/CT scanners possibly allows to overcome the small branching ratio for positron production from 90Y decays and to improve for the post-treatment dosimetry of 90Y of selective internal radiation therapy.

METHODS

For the challenging case of an image quality body phantom, we compare a full Monte Carlo (MC) dose calculation with the results from the two commercial software packages Simplicit90Y and Hermes. The voxel dosimetry module of Hermes relies on the 90Y images taken with a LAFOV PET/CT, while the MC and Simplicit90Y dose calculations are image independent.

RESULTS

The resulting doses from the MC calculation and Simplicit90Y agree well within the error margins. The image-based dose calculation with Hermes, however, consistently underestimates the dose. This is due to the mismatch of the activity distribution in the PET images and the size of the volume of interest. We found that only for the smallest phantom sphere there is a statistically significant dependence of the Hermes dose on the image reconstruction parameters and scan time.

CONCLUSION

Our study shows that Simplicit90Y's local deposition model can provide a reliable dose estimate. On the other hand, the image based dose calculation suffers from the suboptimal reconstruction of the 90Y distribution in small structures.

Predictive Dosimetry and Outcomes of Hepatocellular Carcinoma Treated by Yttrium-90 Resin Microsphere Radioembolization: A Retrospective Analysis Using Technetium-99m Macroaggregated Albumin Single Photon Emission CT/CT and Planning Software

PURPOSE

To characterize estimated mean absorbed tumor dose (ADT), objective response (OR), and estimated target dose of hepatocellular carcinoma (HCC) after resin microsphere yttrium-90 (90Y) radioembolization using partition dosimetry.

MATERIALS AND METHODS

In this retrospective, single-center study, multicompartment dosimetry of index tumors receiving 90Y radioembolization between October 2015 and June 2022 was performed using a commercial software package and pretreatment technetium-99m macroaggregated albumin single photon emission computed tomography (SPECT)/computed tomography (CT). In total, 101 patients with HCC underwent 102 treatments of 127 index tumors. Patients underwent imaging every 2-3 months after treatment to determine best response per modified Response Evaluation Criteria in Solid Tumors (mRECIST). Best response was defined as the greatest response category per mRECIST and categorized as OR or nonresponse (NR). A Cox proportional hazards model evaluated the probability of tumor OR and progression-free survival using ADT.

RESULTS

The median follow-up period was 148 days (interquartile range [IQR], 92-273 days). The median ADT of OR was 141.9 Gy (IQR, 89.4-215.8 Gy) compared with the median ADT of NR treatments of 70.8 Gy (IQR, 42.0-135.3 Gy; P < .001). Only ADT was predictive of response (hazard ratio = 2.79 [95% confidence interval {CI}: 1.44-5.40]; P = .003). At 6 months, an ADT of 157 Gy predicted 90.0% (95% CI: 41.3%-98.3%) probability of OR. At 1 year, an ADT of 157 Gy predicted 91.6% (95% CI: 78.3%-100%) probability of progression-free survival. Partition modeling and delivered activity were predictive of progression (P = .021 and P = .003, respectively).

CONCLUSIONS

For HCC treated with resin microspheres, tumors receiving higher ADT exhibited higher rates of OR. An ADT of 157 Gy predicted 90.0% OR at 6 months.

Transarterial Radioembolization (TARE) in Patients with Hepatocellular Carcinoma: A Comparison of Palliative with Bridging-to-Transplant Concepts

We investigated transarterial radioembolization (TARE) as a palliative measure and bridging-to-transplant therapy in hepatocellular carcinoma (HCC) patients. A total of 167 patients (50 bridging, 117 palliative) with 245 TARE procedures were assessed. Fourteen patients underwent subsequent liver transplantation (LT). Patients undergoing LT exhibited significantly prolonged progression-free survival (PFS) compared to those with bridging-without-transplant (p = 0.033). No significant differences were observed between patients with bridging-without-transplant and palliative cases (p = 0.116). Median overall survival (OS) post-TARE was 16.6 months, with estimated OS rates at 6/12 months of 82.0%/60.5%, respectively. Patients who underwent LT demonstrated statistically significantly longer OS compared to those with bridging-without-transplant (p = 0.001). No marked outcome distinctions were found between bridging-without-transplant and palliative groups. The findings underscored the superiority of LT over alternative treatments. TARE served as an important component in non-LT scenarios, allowing for subsequent therapeutic options. The study reflected the highly variable and complex situations of patients with HCC, emphasizing the need for further investigations to define an optimal multimodal approach.

Hepatopulmonary Shunt Ratio Verification Model for Transarterial Radioembolization

INTRODUCTION

The most important toxicity of transarterial radioembolization therapy applied in liver malignancies is radiation pneumonitis and fibrosis due to hepatopulmonary shunt of Yttrium-90 (90Y) microspheres. Currently, Technetium-99m macroaggregated albumin (99mTc-MAA) scintigraphic images are used to estimate lung shunt fraction (LSF) before treatment. The aim of this study was to create a phantom to calculate exact LFS rates according to 99mTc activities in the phantom and to compare these rates with LSF values calculated from scintigraphic images.

MATERIALS AND METHODS

A 3D-printed lung and liver phantom containing two liver tumors was developed from Polylactic Acid (PLA) material, which is similar to the normal-sized human body in terms of texture and density. Actual %LSFs were calculated by filling phantoms and tumors with 99mTc radionuclide. After the phantoms were placed in the water tank made of plexiglass material, planar, SPECT, and SPECT/CT images were obtained. The actual LSF ratio calculated from the activity amounts filled into the phantom was used for the verification of the quantification of scintigraphic images and the results obtained by the Simplicity90YTM method.

RESULTS

In our experimental model, LSFs calculated from 99mTc activities filled into the lungs, normal liver, small tumor, and large tumor were found to be 0%, 6.2%, 10.8%, and 16.9%. According to these actual LSF values, LSF values were calculated from planar, SPECT/CT (without attenuation correction), and SPECT/CT (with both attenuation and scatter correction) scintigraphic images of the phantom. In each scintigraphy, doses were calculated for lung, small tumor, large tumor, normal liver, and Simplicity90YTM. The doses calculated from planar and SPECT/CT (NoAC+NoSC) images were found to be higher than the actual doses. The doses calculated from SPECT/CT (with AC+with SC) images and Simplicity90YTM were found to be closer to the real dose values.

CONCLUSION

LSF is critical in dosimetry calculations of 90Y microsphere therapy. The newly introduced hepatopulmonary shunt phantom in this study is suitable for LSF verification for all models/brands of SPECT and SPECT/CT devices.

Efficacy of transarterial radioembolization using Y-90 resin microspheres versus atezolizumab-bevacizumab in unresectable hepatocellular carcinoma: A matching-adjusted indirect comparison

INTRODUCTION

No head-to-head trials compared the efficacy of transarterial radioembolization (TARE, also known as selective internal radiation therapy) to combination immunotherapy in hepatocellular carcinoma (HCC). The analysis objective was to compare effectiveness outcomes of TARE using Y-90 resin microspheres and atezolizumab-bevacizumab (AB) in advanced unresectable HCC.

METHODS

Patient-level data from SARAH randomized controlled trial for TARE and aggregate real-world data from AB-real study were used in an unanchored matching-adjusted indirect comparison. The basecase analysis used per-protocol data from SARAH; intention-to-treat data were used in sensitivity analyses. The following prognostic variables and effect modifiers were identified from literature: cause of disease, macrovascular invasion, Eastern Cooperative Oncology Group Performance Status, alpha-fetoprotein level and albumin-bilirubin score. Weights were assigned to patients from SARAH to balance baseline characteristics across studies and reflect characteristics of AB-real patients. Overall survival (OS), progression-free survival (PFS) and response rates (overall response rates [ORR]) were calculated and compared.

RESULTS

The analysis of OS and PFS included 140 patients receiving TARE and 131 for the analysis of response rates, compared to 202 receiving AB. Median OS was 15.0 and 14.9 months for TARE and AB, respectively (HR=0.980; 95% confidence interval [CI]: 0.658-1.461; p-value=0.922). Median PFS was 4.4 and 6.8 months for TARE and AB, respectively (HR=0.745; 95%CI: 0.544-1.022; p-value=0.068). ORR were 19.8% and 25% with TARE and AB, respectively (OR for AB=1.386, 95%CI: 0.746-2.668; p-value=0.306). Sensitivity analyses generated similar results.

CONCLUSION

In HCC patients receiving treatment, TARE using Y-90 resin microspheres may achieve comparable effectiveness outcomes compared with AB.

The contest between internal and external-beam dosimetry: The Zeno's paradox of Achilles and the tortoise

Radionuclide therapy, also called molecular radiotherapy (MRT), has come of age, with several novel radiopharmaceuticals being approved for clinical use or under development in the last decade. External beam radiotherapy (EBRT) is a well-established treatment modality, with about half of all oncologic patients expected to receive at least one external radiation treatment over their disease course. The efficacy and the toxicity of both types of treatment rely on the interaction of radiation with biological tissues. Dosimetry played a fundamental role in the scientific and technological evolution of EBRT, and absorbed doses to the target and to the organs at risk are calculated on a routine basis. In contrast, in MRT the usefulness of internal dosimetry has long been questioned, and a structured path to include absorbed dose calculation is missing. However, following a similar route of development as EBRT, MRT treatments could probably be optimized in a significant proportion of patients, likely based on dosimetry and radiobiology. In the present paper we describe the differences and the similarities between internal and external-beam dosimetry in the context of radiation treatments, and we retrace the main stages of their development over the last decades.

Vortex-assisted resin y90 delivery via 175 cm Truselect microcatheter: case factors for high residual despite double-flush protocol

PURPOSE

To report efficiency of resin y90 delivery using SIROS via 175 cm TruSelect microcatheter with double-flush protocol (40 ml dextrose total).

METHODS

IRB-approved retrospective review of all patients undergoing SIROS injection of y90 Sir-Spheres via TruSelect from 2019 through 2022 at one quaternary-care academic institution, including medical records.

RESULTS

Included were 48 infusions in 25 patients across 11 cancer histologies. Mean planned, delivered, and residual activities were 28 ± 17, 27 ± 17, 1.1 ± 0.56 mCi respectively (mean residual 4.9% ± 2.8%) across flex-dosing precalibrations including 1-day, 2-day, and 3-day SIROS (4/51, 16/51, and 28/51). Mean liver treatment volume was 483 ± 306 ml with target dose mean of 128 ± 26 Gy in non-segmentectomy cases; Radiation segmentectomy was performed in 15/48 (31%). Arterial stasis was documented in 9/48 (19%) of cases. Use of a 3-day precalibrated SIROS dose, use of activity <10 mCi, treatment of smaller liver volumes (<200 ml) and documentation of stasis were associated with higher residual activity ( P  = 0.025, P  = 0.0007, P  = 0.0177, and P  = 0.049, respectively) were associated with higher residuals.

CONCLUSION

Combining the new technologies of SIROS and the Truselect microcatheter with a double-flush protocol yielded <10% residual in 94% of y90 infusions. Future studies may clarify if the predictors of high residual dose seen here may warrant microcatheter-specific considerations for dosimetry or dose preparation at the Radiopharmacy level.