Clinical and dosimetric considerations for Y90: recommendations from an international multidisciplinary working group

Establishing Updated Safety Standards for Independent 99mTc-MAA SPECT/CT Treatment Planning in Radioembolization

PURPOSE

Significant improvements within radioembolization imaging and dosimetry permit the development of an accurate and personalized pretreatment plan using technetium 99m-labeled macroaggregated albumin (99mTc-MAA) and single-photon emission computed tomography (SPECT) combined with anatomical CT (SPECT/CT). Despite these potential advantages, the clinical transition to pretreatment protocols with SPECT/CT is hindered by their unknown safety constraints. This study aimed to address this issue by establishing novel dose limits for 99mTc-MAA SPECT/CT to enable quantitative pretreatment planning.

METHODS AND MATERIALS

Stratification criteria to determine images most viable for dosimetry analysis were created from a cohort of 85 patients. SPECT/CT, cone beam CT, and activity calculations derived from the local deposition method were used to create an accurate pretreatment protocol. Planar and SPECT/CT images were compared using linear regression and modified Bland-Altman analyses to convert accepted planar dose limits to SPECT/CT. To validate these new dose limits, activity calculations based on SPECT/CT were compared with those calculated with the body surface area and planar methods for three treatment plans.

RESULTS

A total of 38 of 85 patients were deemed viable for dosimetry analysis. SPECT yielded greater lung shunt fractions (LSFs) than planar imaging when LSFs were <4.89%, whereas SPECT yielded lower LSFs than planar imaging when LSFs were >4.89%. Planar to SPECT/CT dose conversions were 0.76×, 0.70×, and 0.55× for the whole liver, normal liver, and lungs, respectively. Patients with SPECT LSFs ≤4.89% were safely treated with the direct application of planar lung dose limits. Activity calculations with the newly established SPECT/CT dose limits were greater than those of the body surface area method by a median range of 33.1% to 61.9% and were lower than planar-based activity calculations by a median range of 12.5% to 13.7% for the whole liver and by 29.4% to 32.2% for the normal liver.

CONCLUSIONS

This study demonstrated a safe method for translating dose limits from 99mTc-MAA planar imaging to SPECT/CT. A robust pretreatment protocol was further developed guided by the current knowledge in the field. Established SPECT/CT dose limits safely treated 97.5% of patients and permitted the application of independent pretreatment planning with 99mTc-MAA SPECT/CT.

Transarterial Radioembolization (TARE) Global Practice Patterns: An International Survey by the Cardiovascular and Interventional Radiology Society of Europe (CIRSE)

PURPOSE

An international survey was conducted by the Cardiovascular Interventional Radiological Society of Europe (CIRSE) to evaluate radioembolization practice and capture opinions on real-world clinical and technical aspects of this therapy.

MATERIALS AND METHODS

A survey with 32 multiple choice questions was sent as an email to CIRSE members between November and December 2022. CIRSE group member and sister societies promoted the survey to their local members. The dataset was cleaned of duplicates and entries with missing data, and the resulting anonymized dataset was analysed. Data were presented using descriptive statistics.

RESULTS

The survey was completed by 133 sites, from 30 countries, spanning 6 continents. Most responses were from European centres (87/133, 65%), followed by centres from the Americas (22/133, 17%). Responding sites had been performing radioembolization for 10 years on average and had completed a total of 20,140 procedures over the last 5 years. Hepatocellular carcinoma treatments constituted 56% of this total, colorectal liver metastasis 17% and cholangiocarcinoma 14%. New sites had opened every year for the past 20 years, indicating the high demand for this therapy. Results showed a trend towards individualized treatment, with 79% of responders reporting use of personalized dosimetry for treatment planning and 97% reporting routine assessment of microsphere distribution post-treatment. Interventional radiologists played an important role in referrals, being present in the referring multi-disciplinary team in 91% of responding centres.

CONCLUSION

This survey provides insight into the current state of radioembolization practice globally. The results reveal the increasing significance placed on dosimetry, evolving interventional techniques and increased technology integration.

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.

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.

An international phantom study of inter-site variability in Technetium-99m image quantification: analyses from the TARGET radioembolization study

BACKGROUND

Personalised multi-compartment dosimetry based on [99mTc]Tc-MAA is a valuable tool for planning 90Y radioembolization treatments. The establishment and effective application of dose-effect relationships in yttrium-90 (90Y) radioembolization requires [99mTc]Tc-MAA SPECT quantification ideally independent of clinical site. The purpose of this multi-centre phantom study was to evaluate inter-site variability of [99mTc]Tc-MAA imaging and evaluate a standardised imaging protocol. Data was obtained from the TARGET study, an international, retrospective multi-centre study including 14 sites across 8 countries. The impact of imaging related factors was estimated using a NEMA IQ phantom (representing the liver), and a uniformly filled cylindrical phantom (representing the lungs). Imaging was performed using site-specific protocols and a standardized protocol. In addition, the impact of implementing key image corrections (scatter and attenuation correction) in the site-specific protocols was investigated. Inter-site dosimetry accuracy was evaluated by comparing computed Lung Shunt Fraction (LSF) measured using planar imaging of the cylindrical and NEMA phantom, and contrast recovery coefficient (CRC) measured using SPECT imaging of the NEMA IQ phantom.

RESULTS

Regarding the LSF, inter-site variation with planar site-specific protocols was minimal, as determined by comparing computed LSF between sites (interquartile range 9.6-10.1%). A standardised protocol did not improve variation (interquartile range 8.4-9.0%) but did improve mean accuracy compared to the site-specific protocols (5.0% error for standardised protocol vs 8.8% error for site-specific protocols). Regarding the CRC, inter-system variation was notable for site-specific SPECT protocols and could not be improved by the standardised protocol (CRC interquartile range for 37 mm sphere 0.5-0.7 and 0.6-0.8 respectively), however the standardised protocol did improve accuracy of sphere:background determination. Implementation of key image corrections did improve inter-site variation (CRC interquartile range for 37 mm sphere 0.6-0.7).

CONCLUSION

Eliminating sources of variability in image corrections between imaging protocols reduces inter-site variation in quantification. A standardised protocol was not able to improve consistency of LSF or CRC but was able to improve accuracy.

Outcomes of Y90 Radioembolization for Hepatocellular Carcinoma in Patients Previously Treated with Transarterial Embolization

The aim of this study was to evaluate outcomes of transarterial radioembolization (TARE) for hepatocellular carcinoma (HCC) in patients previously treated with transarterial embolization (TAE). In this retrospective study, all HCC patients who received TARE from 1/2012 to 12/2022 for treatment of residual or recurrent disease after TAE were identified. Overall survival (OS) was estimated using the Kaplan-Meier method. Univariate Cox regression was performed to determine significant predictors of OS after TARE. Twenty-one patients (median age 73.4 years, 18 male, 3 female) were included. Median dose to the perfused liver volume was 121 Gy (112-444, range), and 18/21 (85.7%) patients received 112-140 Gy. Median OS from time of HCC diagnosis was 32.9 months (19.4-61.4, 95% CI). Median OS after first TAE was 29.3 months (15.3-58.9, 95% CI). Median OS after first TARE was 10.6 months (6.8-27.0, 95% CI). ECOG performance status of 0 (p = 0.038), index tumor diameter < 4 cm (p = 0.022), and hepatic tumor burden < 25% (p = 0.018) were significant predictors of longer OS after TARE. TARE may provide a survival benefit for appropriately selected patients with HCC who have been previously treated with TAE.

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.

Direct comparison and reproducibility of two segmentation methods for multicompartment dosimetry: round robin study on radioembolization treatment planning in hepatocellular carcinoma

PURPOSE

Investigate reproducibility of two segmentation methods for multicompartment dosimetry, including normal tissue absorbed dose (NTAD) and tumour absorbed dose (TAD), in hepatocellular carcinoma patients treated with yttrium-90 (90Y) glass microspheres.

METHODS

TARGET was a retrospective investigation in 209 patients with < 10 tumours per lobe and at least one tumour ≥ 3 cm ± portal vein thrombosis. Dosimetry was compared using two distinct segmentation methods: anatomic (CT/MRI-based) and count threshold-based on pre-procedural 99mTc-MAA SPECT. In a round robin substudy in 20 patients with ≤ 5 unilobar tumours, the inter-observer reproducibility of eight reviewers was evaluated by computing reproducibility coefficient (RDC) of volume and absorbed dose for whole liver, whole liver normal tissue, perfused normal tissue, perfused liver, total perfused tumour, and target lesion. Intra-observer reproducibility was based on second assessments in 10 patients ≥ 2 weeks later.

RESULTS

99mTc-MAA segmentation calculated higher absorbed doses compared to anatomic segmentation (n = 209), 43.9% higher for TAD (95% limits of agreement [LoA]: - 49.0%, 306.2%) and 21.3% for NTAD (95% LoA: - 67.6%, 354.0%). For the round robin substudy (n = 20), inter-observer reproducibility was better for anatomic (RDC range: 1.17 to 3.53) than 99mTc-MAA SPECT segmentation (1.29 to 7.00) and similar between anatomic imaging modalities (CT: 1.09 to 3.56; MRI: 1.24 to 3.50). Inter-observer reproducibility was better for larger volumes. Perfused normal tissue volume RDC was 1.95 by anatomic and 3.19 by 99mTc-MAA SPECT, with corresponding absorbed dose RDC 1.46 and 1.75. Total perfused tumour volume RDC was higher, 2.92 for anatomic and 7.0 by 99mTc-MAA SPECT with corresponding absorbed dose RDC of 1.84 and 2.78. Intra-observer variability was lower for perfused NTAD (range: 14.3 to 19.7 Gy) than total perfused TAD (range: 42.8 to 121.4 Gy).

CONCLUSION

Anatomic segmentation-based dosimetry, versus 99mTc-MAA segmentation, results in lower absorbed doses with superior reproducibility. Higher volume compartments, such as normal tissue versus tumour, exhibit improved reproducibility.

TRIAL REGISTRATION

NCT03295006.

Clinical impact of 99mTc-MAA SPECT/CT-based personalized predictive dosimetry in selective internal radiotherapy: a real-life single-center experience in unresectable HCC patients

BACKGROUND

Recent data demonstrated that personalized dosimetry-based selective internal radiotherapy (SIRT) is associated with better outcome for unresectable hepatocellular carcinoma (HCC).

AIM

We aim to evaluate the contribution of personalized predictive dosimetry (performed with Simplicity90® software) in our population of HCC patients by comparing them to our historical cohort whose activity was determined by standard dosimetry.

METHODS

This is a retrospective, single-center study conducted between February 2016 and December 2020 that included patients with HCC who received SIRT after simulation based on either standard dosimetry (group A) or, as of December 2017, on personalized dosimetry (group B). Primary endpoints were best overall response (BOR) and objective response rate (ORR) evaluated by mRECIST at 3 months. Safety and toxicity profiles were evaluated at 1- and 3-months post-treatment. For group A we compared the activity to be administered determined a posteriori using Simplicit90Y® and the activity actually administered determined by the standard approach.

RESULTS

Between February 2016 and December 2020, 66 patients received 69 simulations leading to 40 treatments. The median follow-up time was equal for both groups, 21 months (range 3-55) in group A and 21 months (range 4-39) in group B. The per patient analysis revealed a significant benefit of personalized predictive dosimetry in terms of better overall response at 3 months (80% vs. 33.3%, p = 0.007) and at 6 months (77.8% vs. 22.2%, p = 0.06). This trend was found in the analysis by nodule with a response rate according to mRECIST of 87.5% for personalized dosimetry versus 68.4% for standard dosimetry at 3 months, p = 0.24. Only one grade 3 biological toxicity (hyperbilirubinemia) was noted in group A. The comparison between the administered activity and the recommended activity recalculated a posteriori using Simplicit90Y® showed that the vast majority of patients who progressed (83.33%) received less activity than that recommended by the personalized approach or an inadequate distribution of the administered activity.

CONCLUSIONS

Our study aligns to recent literature and confirms that the use of personalized dosimetry allows a better selection of HCC patients who can benefit from SIRT, and consequently, improves the effectiveness of this treatment.

Factors affecting outcomes of Yttrium-90 radioembolization in heavily pretreated patients with intrahepatic cholangiocarcinoma

PURPOSE

Transarterial radioembolization (TARE) is a liver-directed treatment for unresectable intrahepatic cholangiocarcinoma (ICC). The aim of this study is to evaluate factors affecting outcomes of TARE in heavily pretreated ICC patients.

METHODS

We evaluated pretreated ICC patients who received TARE from January 2013 to December 2021. Prior treatments included systemic therapy, hepatic resection, and liver-directed therapies, including hepatic arterial infusion chemotherapy, external beam radiation, transarterial embolization, and thermal ablation. Patients were classified based on history of hepatic resection and genomic status based on next-generation sequencing (NGS). The primary endpoint was overall survival (OS) after TARE.

RESULTS

Fourteen patients with median age 66.1 years (range, 52.4-87.5), 11 females and 3 males, were included. Prior therapies included systemic in 13/14 patients (93%), liver resection in 6/14 (43%), and liver-directed therapy in 6/14 (43%). Median OS was 11.9 months (range, 2.8-81.0). Resected patients had significantly longer median OS compared to unresected patients (16.6 versus 7.9 months; p = 0.038). Prior liver-directed therapy (p = 0.043), largest tumor diameter > 4 cm (p = 0.014), and > 2 hepatic segments involvement (p = 0.001) were associated with worse OS. Nine patients underwent NGS; 3/9 (33.3%) and had a high-risk gene signature (HRGS), defined as alterations in TP53, KRAS, or CDKN2A. Patients with a HRGS had worse median OS (10.0 versus 17.8 months; p = 0.024).

CONCLUSIONS

TARE may be used as salvage therapy in heavily treated ICC patients. Presence of a HRGS may predict worse OS after TARE. Further investigation with more patients is recommended to validate these results.

Outcomes of Radiation Segmentectomy for Hepatocellular Carcinoma in Patients with Non-Alcoholic Fatty Liver Disease versus Chronic Viral Hepatitis

Purpose

To compare the outcomes of radiation segmentectomy for early-stage hepatocellular carcinoma (HCC) in patients with non-alcoholic fatty liver disease (NAFLD) versus hepatitis C virus (HCV).

Materials and Methods

A retrospective analysis of consecutive patients with NAFLD- or HCV-related HCC treated with radiation segmentectomy from 01/2017-06/2022 was performed. Eligibility criteria included solitary tumor ≤8 cm or up to 3 HCC ≤3 cm, ECOG 0-1, and absence of vascular invasion or extrahepatic spread. Imaging best response was assessed per modified Response Evaluation Criteria in Solid Tumors. Target tumor and overall progression, time-to-progression (TTP), and overall survival (OS) were calculated. All outcomes were censored for liver transplantation (LT). Complete pathologic response (CPN) was assessed in patients who underwent LT.

Results

Of 142 patients included (NAFLD: 61; HCV: 81), most had cirrhosis (NAFLD: 87%; HCV: 86%) and small tumors (median size NAFLD: 2.3 cm; HCV: 2.5 cm). Patients with NAFLD had higher BMI (p<0.001) and worse ALBI scores (p=0.003). Patients with HCV were younger (p<0.001) and had higher AFP levels (p=0.034). Median radiation dose (NAFLD: 508 Gy; HCV: 452 Gy) and specific activity (NAFLD: 700 Bq; HCV: 698 Bq) were similar between cohorts. Objective response was 100% and 97% in the NAFLD and HCV cohorts, respectively. Target tumor progression occurred in 1 (2%) NAFLD and 8 (10%) HCV patients. Target tumor TTP was not met for either cohort. Overall progression occurred in 23 (38%) NAFLD and 39 (48%) HCV patients. Overall TTP was 17.4 months (95% CI 13.5-22.2) in NAFLD and 13.5 months (95% CI 0.4-26.6) in HCV patients (p=0.86). LT was performed in 27 (44%) NAFLD and 33 (41%) HCV patients, with a CPN rate of 63% and 54%, respectively. OS was not met in the NAFLD cohort and was 53.9 months (95% CI 32.1-75.7) in the HCV cohort (p=0.15).

Conclusion

Although NAFLD and HCV are associated with different mechanisms of liver injury, patients with early-stage HCC treated with radiation segmentectomy achieve comparable outcomes.

Surgery and radioembolization of liver tumors

Surgical resection is considered the curative treatment par excellence for patients with primary or metastatic liver tumors. However, less than 40% of them are candidates for surgery, either due to non-modifiable factors (comorbidities, age, liver dysfunction…), or to the invasion or proximity of the tumor to the main vascular requirements, the lack of a future liver remnant (FLR) adequate to maintain postoperative liver function, or criteria of tumor size and number. In these last factors, hepatic radioembolization has been shown to play a role as a presurgical tool, either by hypertrophy of the FLR or by reducing tumor size that manages to reduce tumor staging (term known as "downstaging"). To these is added a third factor, which is its ability to apply the test of time, which makes it possible to identify those patients who present progression of the disease in a short period of time (both locally and at distance), avoiding a unnecessary surgery. This paper aims to review RE as a tool to facilitate liver surgery, both through the experience of our center and the available scientific evidence.

Voxel-Based Dosimetry Predicts Hepatotoxicity in Hepatocellular Carcinoma Patients Undergoing Radioembolization with 90Y Glass Microspheres

Personalized dosimetry holds promise to improve radioembolization treatment outcomes in hepatocellular carcinoma (HCC) patients. To this end, tolerance absorbed doses for nontumor liver tissue are assessed by calculating the mean absorbed dose to the whole nontumor liver tissue (AD-WNTLT), which may be limited by its neglect of nonuniform dose distribution. Thus, we analyzed whether voxel-based dosimetry could be more accurate in predicting hepatotoxicity in HCC patients undergoing radioembolization. Methods: In total, 176 HCC patients were available for this retrospective analysis; of these, 78 underwent partial- and 98 whole-liver treatment. Posttherapeutic changes in bilirubin were graded using the Common Terminology Criteria for Adverse Events. We performed voxel-based and multicompartment dosimetry using pretherapeutic ^99mTc-labeled human serum albumin SPECT and contrast-enhanced CT/MRI and defined the following dosimetry parameters: AD-WNTLT; the nontumor liver tissue volume exposed to at least 20 Gy (V20), at least 30 Gy (V30), and at least 40 Gy (V40); and the threshold absorbed dose to the 20% (AD-20) and 30% (AD-30) of nontumor liver tissue with the lowest absorbed dose. Their impact on hepatotoxicity after 6 mo was analyzed using the area under the receiver-operating-characteristic curve; thresholds were identified using the Youden index. Results: The area under the curve for prediction of posttherapeutic grade 3+ increases in bilirubin was acceptable for V20 (0.77), V30 (0.78), and V40 (0.79), whereas it was low for AD-WNTLT (0.67). The predictive value could further be increased in the subanalysis of patients with whole-liver treatment, where a good discriminatory power was found for V20 (0.80), V30 (0.82), V40 (0.84), AD-20 (0.80), and AD-30 (0.82) and an acceptable discriminatory power was found for AD-WNTLT (0.63). The accuracies of V20 (P = 0.03), V30 (P = 0.009), V40 (P = 0.004), AD-20 (P = 0.04), and AD-30 (P = 0.02) were superior to that of AD-WNTLT but did not differ significantly from each other. The respective thresholds were 78% (V30), 72% (V40), and 43 Gy (AD-30). Statistical significance was not reached for partial-liver treatment. Conclusion: Voxel-based dosimetry may more accurately predict hepatotoxicity than multicompartment dosimetry in HCC patients undergoing radioembolization, which could enable dose escalation or deescalation with the intent to optimize treatment response. Our results indicate that a V40 of 72% may be particularly useful in whole-liver treatment. However, further research is warranted to validate these results.

Single-Compartment Dose Prescriptions for Ablative 90Y-Radioembolization Segmentectomy

BACKGROUND

Yttrium-90 (⁹⁰Y) radioembolization is increasingly being utilized with curative intent. While single-compartment doses with respect to the perfused volume for the complete pathologic necrosis (CPN) of tumors have been reported, the actual doses delivered to the tumor and at-risk margins that leads to CPN have hitherto not been estimated. We present an ablative dosimetry model that calculates the dose distribution for tumors and at-risk margins based on numerical mm-scale dose modeling and the available clinical CPN evidence and report on the necessary dose metrics needed to achieve CPN following ⁹⁰Y-radioembolization.

METHODS

Three-dimensional (3D) activity distributions (MBq/voxel) simulating spherical tumors were modeled with a 121 × 121 × 121 mm³ soft tissue volume (1 mm³ voxels). Then, 3D dose distributions (Gy/voxel) were estimated by convolving 3D activity distributions with a ⁹⁰Y 3D dose kernel (Gy/MBq) sized 61 × 61 × 61 mm³ (1 mm³ voxels). Based on the published data on single-compartment segmental doses for the resected liver samples of HCC tumors showing CPN after radiation segmentectomy, the nominal voxel-based mean tumor dose (DmeanCPN), point dose at tumor rim (DrimCPN), and point dose 2 mm beyond the tumor boundary (D2mmCPN), which are necessary to achieve CPN, were calculated. The single-compartment dose prescriptions to required achieve CPN were then analytically modeled for more general cases of tumors with diameters dt = 2, 3, 4, 5, 6, and 7 cm and with tumor-to-normal-liver uptake ratios T:N = 1:1, 2:1, 3:1, 4:1, and 5:1.

RESULTS

The nominal case defined to estimate the doses needed for CPN, based on the previously published clinical data, was a single hyperperfused tumor with a diameter of 2.5 cm and T:N = 3:1, treated with a single-compartment segmental dose of 400 Gy. The voxel-level doses necessary to achieve CPN were 1053 Gy for the mean tumor dose, 860 Gy for the point dose at the tumor boundary, and 561 Gy for the point dose at 2 mm beyond the tumor edge. The single-compartment segmental doses necessary to satisfy the criteria for CPN in terms of the mean tumor dose, point dose at the tumor boundary, and the point dose at 2 mm beyond the tumor edge were tabulated for a range of tumor diameters and tumor-to-normal-liver uptake ratios.

CONCLUSIONS

The analytical functions that describe the relevant dose metrics for CPN and, more importantly, the single-compartment dose prescriptions for the perfused volume needed to achieve CPN are reported for a large range of conditions in terms of tumor diameters (1-7 cm) and T:N uptake ratios (2:1-5:1).

Personalized 90 Y-resin microspheres dose determination: a retrospective study on the impact of dosimetry software on the treatment of patients with selective internal radiotherapy

INTRODUCTION

The calculation of resin yttrium-90 ( 90 Y-) microspheres activity for selective internal radiotherapy (SIRT) needs to be investigated.

METHODS AND MATERIALS

Analyses using Simplicit 90 Y (Boston Scientific, Natick, Massachusetts, USA) dosimetry software were performed to determine the concordance between the absorbed doses to the tumor (D T1 and D T2 ) and healthy liver (D N1 and D N2 ) during the pre-treatment and the post-treatment phases. An optimized calculation of the activity of 90 Y-microspheres performed using dosimetry software was applied retrospectively to assess the impact of this calculation method on the treatment.

RESULTS

D T1 ranged from 38.8 to 372 Gy, with a mean value of 128.9 ± 73.6 Gy and median of 121.2 Gy [interquartile range (IQR): 81.7-158.8 Gy]. The median D N1 and D N2 was 10.5 Gy (IQR: 5.8-17.6). A significant correlation was between D T1 and D T2 ( r  = 0.88, P  < 0.001) and D N1 and D N2 ( r  = 0.96, P  < 0.001). The optimized activities were calculated; the target dose to the tumor compartment was 120 Gy. No activity reduction was applied in accordance with the tolerance of the healthy liver. Optimization of the microspheres dosages would have resulted in a significant increase in activity for nine treatments (0.21-2.54 GBq) and a reduction for seven others (0.25-0.76 GBq).

CONCLUSIONS

The development of customized dosimetry software adapted to clinical practice makes it possible to use dosimetry to optimize the dosage for each patient.

Boosted-Dose Yttrium-90 Radiation Segmentectomy or Lobectomy for Hepatocellular Carcinoma Refractory to Prior Transarterial Embolization or Chemoembolization: A Single Institution Retrospective Case Series

PURPOSE

To assess the tumor response rates and liver toxicity of boosted-dose transarterial radioembolization (TARE) for treatment of hepatocellular carcinoma (HCC) refractory to previous transarterial embolization (TAE) and/or chemoembolization (TACE).

MATERIALS AND METHODS

All patients were identified who had HCC treated between 2017 and 2020 that had been refractory to prior TAE or TACE, then treated with boosted-dose segmental or lobar TARE. Tumor response was assessed by multiphasic CT or MRI using localized mRECIST imaging criteria and serological alpha-fetoprotein levels at three and six months after TARE, if available. Liver toxicity was evaluated using serial serological liver function tests, platelet counts, and clinical Child-Pugh and MELD scores.

RESULTS

Twenty-four patients met inclusion criteria. Mean age was 68.7 years (54-89); 8 were females. Three (12.5%) patients had Barcelona Clinical Liver Cancer stage A, 4 (16.7%) stage B, and 17 (70.8%) stage C disease. Three months after TARE, 52% of patients had a complete response and 33% had a partial response. Mean AFP decreased from 33.2 ng/mL at baseline to 17 ng/mL at 3 months (p = 0.782). The median MELD-Na score increased from 11 at baseline to 16 at 6 months post-TARE (p = 0.044); the mean Child-Pugh score rose from 5 at baseline to 6 at 3 months post-TARE (p < 0.01).

CONCLUSION

Boosted-dose TARE resulted in statistically significant favorable tumor responses by imaging criteria in 85% of patients previously refractory to TAE or TACE. TARE resulted in transient but acceptable deterioration of liver function and clinical scores.

Dosimetric impact of 3D motion-compensated SPECT reconstruction for SIRT planning

BACKGROUND

In selective internal radiation therapy, ^99mTc SPECT images are used to optimize patient treatment planning, but they are affected by respiratory motion. In this study, we evaluated on patient data the dosimetric impact of motion-compensated SPECT reconstruction on several volumes of interest (VOI), on the tumor-to-normal liver (TN) ratio and on the activity to be injected.

METHODS

Twenty-nine patients with liver cancer or hepatic metastases treated by radioembolization were included in this study. The biodistribution of ⁹⁰Y is assumed to be the same as that of ^99mTc when predictive dosimetry is implemented. A total of 31 ^99mTc SPECT images were acquired and reconstructed with two methods: conventional OSEM (3D) and motion-compensated OSEM (3Dcomp). Seven VOI (liver, lungs, tumors, perfused liver, hepatic reserve, healthy perfused liver and healthy liver) were delineated on the CT or obtained by thresholding SPECT images followed by Boolean operations. Absorbed doses were calculated for each reconstruction using Monte Carlo simulations. Percentages of dose difference (PDD) between 3Dcomp and 3D reconstructions were estimated as well as the relative differences for TN ratio and activities to be injected. The amplitude of movement was determined with local rigid registration of the liver between the 3Dcomp reconstructions of the extreme phases of breathing.

RESULTS

The mean amplitude of the liver was 9.5 ± 2.7 mm. Medians of PDD were closed to zero for all VOI except for lungs (6.4%) which means that the motion compensation overestimates the absorbed dose to the lungs compared to the 3D reconstruction. The smallest lesions had higher PDD than the largest ones. Between 3D and 3Dcomp reconstructions, means of differences in lung dose and TN ratio were not statistically significant, but in some cases these differences exceed 1 Gy (4/31) and 8% (2/31). The absolute differences in activity were on average 3.1% ± 5.1% and can reach 22.8%.

CONCLUSION

The correction of respiratory motion mainly impacts the lung and tumor doses but only for some patients. The largest dose differences are observed for the smallest lesions.

Maximum tumor-absorbed dose measured by voxel-based multicompartmental dosimetry as a response predictor in yttrium-90 radiation segmentectomy for hepatocellular carcinoma

OBJECTIVE

Advances in hepatic radioembolization are based on a selective approach with radical intent and the use of multicompartment dosimetric analysis. The objective of this study is to assess the utility of voxel-based dosimetry in the quantification of actual absorbed doses in radiation segmentectomy procedures and to establish cutoff values predictive of response.

METHODS

Ambispective study in hepatocarcinoma patients treated with radiation segmentectomy. Calculated dosimetric parameters were mean tumor-absorbed dose, maximum tumor AD, minimal tumor AD in 30, 50, and 70% of tumor volume and mean AD in non-tumor liver. The actual absorbed dose (aAD) was calculated on the Y-90-PET/CT image using 3D voxel-based dosimetry software. To assess radiological response, localized mRECIST criteria were used. The objective response rate (ORR) was defined as CR or PR.

RESULTS

Twenty-four HCC patients, BCLC 0 (5), A (17) and B (2) were included. The mean yttrium-90 administered activity was 1.38 GBq in a mean angiosome volume of 206.9 cc and tumor volume 56.01 cc. The mean theoretical AD was 306.3 Gy and aAD 352 Gy. A very low concordance was observed between both parameters (rho_c 0.027). ORR at 3 and 6 m was 84.21% and 92.31%, respectively. Statistically significant relationship was observed between the maximum tumor-absorbed dose and complete radiological response at 3 m (p 0.022).

CONCLUSION

A segmental approach with radical intention leads to response rates greater than 90%, being the tumor maximum absorbed dose the dosimetric parameter that best predicts radiological response in voxel-based dosimetry.

Accuracy and reproducibility of a cone beam CT-based virtual parenchymal perfusion algorithm in the prediction of SPECT/CT anatomical and volumetric results during the planification of radioembolization for HCC

OBJECTIVES

To evaluate anatomical and volumetric predictability of a cone beam computed tomography (CBCT)-based virtual parenchymal perfusion (VPP) software for the single-photon-emission computed tomography (SPECT)/CT imaging results during the work-up for transarterial radioembolization (TARE) procedure in patients with hepatocellular carcinoma (HCC).

METHODS

VPP was evaluated retrospectively on CBCT data of patients treated by TARE for HCC. ^99mTc macroaggregated albumin particles (^99mTc-MAA) uptake territories on work-up SPECT/CT was used as ground truth for the evaluation. Semi-quantitative evaluation consisted of the ranking of visual consistency of the parenchymal enhancement and portal vein tumoral involvement on VPP and ^99mTc-MAA SPECT/CT, using a three-rank scale and two-rank scale, respectively. Inter-reader agreement was evaluated using a kappa coefficient. Quantitative evaluation included absolute volume error calculation and Pearson correlation between volumes enhanced territories on VPP and ^99mTc-MAA SPECT/CT.

RESULTS

Fifty-two CBCTs were performed in 33 included patients. Semi-quantitative evaluation showed a good concordance between actual ^99mTc-MAA uptake and the virtual enhanced territories in 73% and 75% of cases; a mild concordance in 12% and 10% and a poor concordance in 15%, for the two readers. Kappa coefficient was 0.86. Portal vein involvement evaluation showed a good concordance in 58.3% and 66.7% for the two readers, respectively, with a kappa coefficient of 0.82. Quantitative evaluation showed a volume error of 0.46 ± 0.78 mL [0.01-3.55], and Pearson R² factor at 0.75 with a p value < 0.01.

CONCLUSION

CBCT-based VPP software is accurate and reliable to predict ^99mTc-MAA SPECT/CT anatomical and volumetric results in HCC patients during TARE.

KEY POINTS

• Virtual parenchymal perfusion (VPP) software is accurate and reliable in the prediction of ^99mTc-MAA SPECT volumetric and targeting results in HCC patients during transarterial radioembolization (TARE). • VPP software may be used per-operatively to optimize the microcatheter position for ⁹⁰Y infusion allowing precise tumor targeting while preserving non-tumoral parenchyma. • Post-operatively, VPP software may allow an accurate estimation of the perfused volume by each arterial branch and, thus, a precise ⁹⁰Y dosimetry for TARE procedures.

Clinical, dosimetric, and reporting considerations for Y-90 glass microspheres in hepatocellular carcinoma: updated 2022 recommendations from an international multidisciplinary working group

PURPOSE

In light of recently published clinical reports and trials, the TheraSphere Global Dosimetry Steering Committee (DSC) reconvened to review new data and to update previously published clinical and dosimetric recommendations for the treatment of hepatocellular carcinoma (HCC).

METHODS

The TheraSphere Global DSC is comprised of health care providers across multiple disciplines involved in the treatment of HCC with yttrium-90 (Y-90) glass microsphere-based transarterial radioembolization (TARE). Literature published between January 2019 and September 2021 was reviewed, discussed, and adjudicated by the Delphi method. Recommendations included in this updated document incorporate both the results of the literature review and the expert opinion and experience of members of the committee.

RESULTS

Committee discussion and consensus led to the expansion of recommendations to apply to five common clinical scenarios in patients with HCC to support more individualized efficacious treatment with Y-90 glass microspheres. Existing clinical scenarios were updated to reflect recent developments in dosimetry approaches and broader treatment paradigms evolving for patients presenting with HCC.

CONCLUSION

Updated consensus recommendations are provided to guide clinical and dosimetric approaches for the use of Y-90 glass microsphere TARE in HCC, accounting for disease presentation, tumor biology, and treatment intent.

Yttrium-90 Radioembolization: Current Indications and Outcomes

BACKGROUND

Radioembolization (RE) with 90Yttrium (Y90) has generally been used to treat patients with advanced disease. Recent data suggest, however, that RE is also safe and feasible to treat patients with early or intermediate stage disease. We herein review the current evidence regarding the use of RE with Y90 for patients with HCC.

METHODS

A comprehensive review of the literature was performed using MEDLINE/PubMed and Web of Science databases with a search end date of August 1, 2022.

RESULTS

Patients with HCC are often treated according to the BCLC staging system. Among patients with early-stage HCC (BCLC A), intermediate-stage HCC (BCLC B), and advanced-stage HCC (BCLC C), RE with Y90 has demonstrated promising results with comparable overall survival, time to disease progression, and radiological response compared with other standard of care treatment modalities. Moreover, Y90 RE can be used as a downstaging treatment modality for patients with advanced HCC who have a disease burden that is initially outside LT criteria. Radiation lobectomy (RL) has been described as a treatment modality with the intent of treating the ipsilateral liver that harbors the HCC, while also causing compensatory hypertrophy of the future liver remnant (FLR).

CONCLUSION

While initially considered as a palliative option for HCC patients, Y90 RE has emerged as an important part of the multi-modality care of patients with HCC across a wide spectrum of clinical indications.

Phase I prospective trial of TAS-102 (trifluridine and tipiracil) and radioembolization with 90Y resin microspheres for chemo-refractory colorectal liver metastases

BACKGROUND

Extrahepatic disease progression limits clinical efficacy of Yttrium-90 (⁹⁰Y) radioembolization (TARE) for patients with chemotherapy-refractory metastatic colorectal cancer (mCRC). Trifluridine and tipiracil (TAS-102) has overall survival benefit for patients with refractory mCRC and may be a radiosensitizer.

METHODS

Sequential lobar TARE using ⁹⁰Y resin microspheres in combination with TAS-102 in 28-day cycles were used to treat adult patients with bilobar liver-dominant chemo-refractory mCRC according to 3 + 3 dose escalation design with a 12-patient dose expansion cohort. Study objectives were to establish safety and determine maximum tolerated dose (MTD) of TAS-102 in combination with TARE.

RESULTS

A total of 21 patients (14 women, 7 men) with median age of 60 years were enrolled. No dose limiting toxicities were observed. Treatment related severe adverse events included cytopenias (10 patients, 48%) and radioembolization-induced liver disease (2 patients, 10%). Disease control rate in the liver lobes treated with TARE was 100%. Best observed radiographic responses were partial response for 4 patients (19%) and stable disease for 12 patients (57%).

CONCLUSIONS

The combination of TAS-102 and TARE for patients with liver-dominant mCRC is safe and consistently achieves disease control within the liver.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT02602327 (first posted 11/11/2015).

Safety and Efficacy of 166Ho Radioembolization in Hepatocellular Carcinoma: The HEPAR Primary Study

The safety and efficacy of ¹⁶⁶Ho radioembolization was first determined in the HEPAR and HEPAR II studies, which, however, excluded patients with hepatocellular carcinoma (HCC). The aim of this prospective clinical early phase II study was to establish the toxicity profile of ¹⁶⁶Ho radioembolization in patients with measurable, liver-dominant HCC; Barcelona clinic liver cancer stage B or C; a Child-Pugh score of no more than B7; and an Eastern Cooperative Oncology Group performance status of 0-1 without curative treatment options. Methods: The primary endpoint was a rate of unacceptable toxicity defined as grade 3 hyperbilirubinemia (Common Terminology Cancer Adverse Events, version 4.03) in combination with a low albumin or ascites level in the absence of disease progression or treatment-related serious adverse events. Secondary endpoints included overall toxicity, response, survival, change in α-fetoprotein, and quality of life. Thirty-one patients with Barcelona clinic liver cancer stage B (71%) or C (29%) HCC were included, mostly multifocal (87%) or bilobar (55%) disease. Results: Common grade 1 or 2 clinical toxicity included fatigue (71%), back pain (55%), ascites (32%), dyspnea (23%), nausea (23%), and abdominal pain (23%), with no more than 10% grade 3-5 toxicity. Grade 3 laboratory toxicity (>10%) included an aspartate transaminase and γ-glutamyltransferase increase (16%), hyperglycemia (19%), and lymphopenia (29%). Treatment-related unacceptable toxicity occurred in 3 of 31 patients. At 3 mo, 54% of target lesions showed a complete or partial response according to modified RECIST. Median overall survival was 14.9 mo (95% CI, 10.4-24.9 mo). No significant changes in quality of life or pain were observed. Conclusion: The safety of ¹⁶⁶Ho radioembolization was confirmed in HCC, with less than 10% unacceptable toxicity. Efficacy data support further evaluation.

Role of interventional oncology in hepatocellular carcinoma: Future best practice beyond current guidelines

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related deaths globally. Liver transplant remains the goal of curative treatment, but limited supply of organs decreases accessibility and prolongs waiting time to transplantation. Therefore, interventional oncology therapies have been used to treat the majority of HCC patients, including those awaiting transplant. The Barcelona Clinic Liver Cancer (BCLC) classification is the most widely used staging system in management of HCC that helps allocate treatments. Since its inception in 1999, it was updated for the fifth time in November 2021 and for the first time shaped by expert opinions outside the core BCLC group. The most recent version includes additional options for early-stage disease, substratifies intermediate disease into three groups, and lists alternates to Sorafenib that can double the expected survival of advanced-stage disease. The group also proposed a new BCLC staging schema for disease progression, and endorsed treatment stage migration (TSM) directly into the main staging and treatment algorithm. This article reviews the recent developments underlying the current BCLC guidelines and highlights ongoing research, particularly involving radioembolization, that will shape future best practice.

The American Brachytherapy Society consensus statement for permanent implant brachytherapy using Yttrium-90 microsphere radioembolization for liver tumors

PURPOSE

To develop a multidisciplinary consensus for high quality multidisciplinary implementation of brachytherapy using Yttrium-90 (90Y) microspheres transarterial radioembolization (90Y TARE) for primary and metastatic cancers in the liver.

METHODS AND MATERIALS

Members of the American Brachytherapy Society (ABS) and colleagues with multidisciplinary expertise in liver tumor therapy formulated guidelines for 90Y TARE for unresectable primary liver malignancies and unresectable metastatic cancer to the liver. The consensus is provided on the most recent literature and clinical experience.

RESULTS

The ABS strongly recommends the use of 90Y microsphere brachytherapy for the definitive/palliative treatment of unresectable liver cancer when recommended by the multidisciplinary team. A quality management program must be implemented at the start of 90Y TARE program development and follow-up data should be tracked for efficacy and toxicity. Patient-specific dosimetry optimized for treatment intent is recommended when conducting 90Y TARE. Implementation in patients on systemic therapy should account for factors that may enhance treatment related toxicity without delaying treatment inappropriately. Further management and salvage therapy options including retreatment with 90Y TARE should be carefully considered.

CONCLUSIONS

ABS consensus for implementing a safe 90Y TARE program for liver cancer in the multidisciplinary setting is presented. It builds on previous guidelines to include recommendations for appropriate implementation based on current literature and practices in experienced centers. Practitioners and cooperative groups are encouraged to use this document as a guide to formulate their clinical practices and to adopt the most recent dose reporting policies that are critical for a unified outcome analysis of future effectiveness studies.

Trans-arterial Radioembolization Dosimetry in 2022

Trans-arterial radioembolization is currently performed using ⁹⁰Y-loaded glass or resin microspheres and also using ¹⁶⁶Ho-loaded microspheres. The goal of this review is to present dosimetry and radiobiology concepts, the different dosimetry approaches available (simulation-based dosimetry and post-treatment dosimetry), main confounding factors as main clinical dosimetry results provided during the last decade for both hepatocellular carcinoma (HCC) and metastases of colorectal carcinoma (mCRC). Based on the different number of microspheres or different isotope used, radiobiology of the three devices is different, meaning that tumouricidal doses and maximal tolerated doses are different. Tumouricidal doses described for HCCs were 100-120 grays (Gy) with ⁹⁰Y resin microspheres and 205 Gy with ⁹⁰Y glass microspheres. For mCRC, it is 39-60 with ⁹⁰Y resin microspheres, 139 Gy with ⁹⁰Y glass microspheres and 90 Gy with ¹⁶⁶Ho microspheres. An impact of tumoural doses with overall survival has also been reported. Personalised dosimetry has been developed and is now recommended by several international expert groups. Level-one evidence of the major impact of personalised dosimetry on response and overall survival in HCC is now available, bringing a new standard approach for TARE in clinical practice as well as for trial design.

Intraprocedural MRI-based dosimetry during transarterial radioembolization of liver tumours with holmium-166 microspheres (EMERITUS-1): a phase I trial towards adaptive, image-controlled treatment delivery

PURPOSE

Transarterial radioembolization (TARE) is a treatment for liver tumours based on injection of radioactive microspheres in the hepatic arterial system. It is crucial to achieve a maximum tumour dose for an optimal treatment response, while minimizing healthy liver dose to prevent toxicity. There is, however, no intraprocedural feedback on the dose distribution, as nuclear imaging can only be performed after treatment. As holmium-166 (¹⁶⁶Ho) microspheres can be quantified with MRI, we investigate the feasibility and safety of performing ¹⁶⁶Ho TARE within an MRI scanner and explore the potential of intraprocedural MRI-based dosimetry.

METHODS

Six patients were treated with ¹⁶⁶Ho TARE in a hybrid operating room. Per injection position, a microcatheter was placed under angiography guidance, after which patients were transported to an adjacent 3-T MRI system. After MRI confirmation of unchanged catheter location, ¹⁶⁶Ho microspheres were injected in four fractions, consisting of 10%, 30%, 30% and 30% of the planned activity, alternated with holmium-sensitive MRI acquisition to assess the microsphere distribution. After the procedures, MRI-based dose maps were calculated from each intraprocedural image series using a dedicated dosimetry software package for ¹⁶⁶Ho TARE.

RESULTS

Administration of ¹⁶⁶Ho microspheres within the MRI scanner was feasible in 9/11 (82%) injection positions. Intraprocedural holmium-sensitive MRI allowed for tumour dosimetry in 18/19 (95%) of treated tumours. Two CTCAE grade 3-4 toxicities were observed, and no adverse events were attributed to treatment in the MRI. Towards the last fraction, 4/18 tumours exhibited signs of saturation, while in 14/18 tumours, the microsphere uptake patterns did not deviate from the linear trend.

CONCLUSION

This study demonstrated feasibility and preliminary safety of a first in-human application of TARE within a clinical MRI system. Intraprocedural MRI-based dosimetry enabled dynamic insight in the microsphere distribution during TARE. This proof of concept yields unique possibilities to better understand microsphere distribution in vivo and to potentially optimize treatment efficacy through treatment personalization.

REGISTRATION

Clinicaltrials.gov, identifier NCT04269499, registered on February 13, 2020 (retrospectively registered).

Conversion to resection post radioembolization in patients with HCC: recommendations from a multidisciplinary working group

BACKGROUND

Transarterial radioembolization (TARE) with yttrium-90 (⁹⁰Y) glass microspheres is an efficacious option for converting appropriately selected patients with borderline-resectable hepatocellular carcinoma (HCC) to surgical candidacy.

METHODS

In 2018 and 2019, a diverse multidisciplinary group of surgical and interventional experts with experience using ⁹⁰Y for downstaging and bridging to liver transplant convened to review peer-reviewed literature and personal experience in the use of ⁹⁰Y to convert borderline resectable liver cancer patients to surgical candidacy. The working group included surgical oncologists specializing in liver cancer, liver transplant surgeons with experience in complex hepatobiliary surgery, and interventional radiologists with experience using ⁹⁰Y.

RESULTS

This document presents expert recommendations based upon the group's experience and consensus.

CONCLUSIONS

By combining related evidence from the literature with expert experiences with TARE in surgical candidates, these recommendations aim to demonstrate the safety, efficacy, and feasibility of TARE in converting borderline-resectable patients to surgical options. The document also addresses the concerns about potential complications associated with TARE during the surgical intervention.

Clinical Outcomes of Patients With Unresectable Primary Liver Cancer Treated With Yttrium-90 Radioembolization With an Escalated Dose

Purpose

Yttrium-90 (90Y) radioembolization with an escalated dose has been shown to improve clinical outcomes compared with standard dose radioembolization, but there are few data on the local control of primary liver tumors. We reported the clinical outcomes of patients with unresectable primary liver tumors treated with 90Y radioembolization with an escalated dose.

Methods and Materials

Clinical data of patients with unresectable hepatocellular carcinoma (HCC), cholangiocarcinoma (CC), and biphenotypic tumors (cHCC-CC) treated with radioembolization with an escalated dose (≥150 Gy) between 2013 and 2020 with >3 months follow-up were retrospectively reviewed. The primary endpoint was freedom from local progression. Clinical response was defined by Modified Response Evaluation Criteria in Solid Tumours and toxic effects were assessed using Common Terminology Criteria for Adverse Events version 5.0.

Results

Fifty-three patients with HCC and 15 patients with CC/cHCC-CC were analyzed. The median dose delivered was 205 Gy (interquartile range, 183-253 Gy) and 198 Gy (interquartile range, 154-234 Gy) for patients with HCC and CC/cHCC-CC, respectively. The 1-year freedom from local progression rate was 54% (95% confidence interval [CI], 38%-78%) for patients with HCC and 66% (95% CI, 42%-100%) for patients with CC/cHCC-CC. For patients with HCC, United Network for Organ Sharing nodal stage 1 (P = .01), nonsolitary tumors (P = .02), pretreatment α-fetoprotein of >7.7 ng/mL (P = .006), and ≤268 Gy dose delivered (P = .003) were predictors for local progression on multivariate Cox analysis. No patients with HCC who received a dose >268 Gy had a local tumor progression. The 1-year overall survival for patients with HCC was 74% (95% CI, 61%-89%). After radioembolization, 5 (7%) patients had grade 3 ascites, and 4 (6%) patients had grade 3/4 hyperbilirubinemia.

Conclusions

Treatment of unresectable primary liver tumors with 90Y radioembolization with an escalated dose was safe and well tolerated. Delivery of >268 Gy may improve local tumor control of HCC. Determination of the maximum tolerated dose needs to be performed in the context of future prospective dose-escalation trials to further evaluate the safety and efficacy of such an approach.

Selective Internal Radiation Therapy with Yttrium-90 Resin Microspheres Followed by Gemcitabine plus Cisplatin for Unresectable Intrahepatic Cholangiocarcinoma: A Phase 2 Single-Arm Multicenter Clinical Trial

INTRODUCTION

This investigator-initiated clinical trial aims to study the efficacy and safety of administering selective internal radiation therapy with resin yttrium-90 microspheres (SIRT) followed by standard chemotherapy in unresectable intrahepatic cholangiocarcinoma (ICC).

METHODS

A phase 2 single-arm multicenter study was conducted in patients with unresectable ICC (NCT02167711). SIRT was administered at dose of 120 Gy targeted at tumor followed by commencement of gemcitabine 1,000 mg/m² and cisplatin 25 mg/m² on days one and eight of a 21-day cycle. The primary endpoint was overall survival (OS), and the secondary endpoints include progression-free survival (PFS), response rate according to Response Evaluation Criteria in solid tumors 1.1, toxicity, and time from SIRT to commencement of chemotherapy.

RESULTS

Total 31 patients were screened and twenty-four were recruited. All patients completed SIRT and 16 of them underwent subsequent chemotherapy. The median cycle of chemotherapy was 5 (range: 1-8). The median OS was 13.6 months (95% CI: 5.4-21.6) for the intent-to-treat population. Among 16 patients undergoing chemotherapy, the median OS was 21.6 months (95% CI: 7.3-25.2) and the median PFS was 9 months (95% CI: 3.2-13.1). The response rate was 25% (95% CI: 3.8-46.2%), and the disease control rate was 75% (95% CI: 53.8-96.2%). No new safety signal was observed, with fewer than 10% of patients suffering from grade 3 or higher treatment-related adverse events. The median time from SIRT to chemotherapy was 29 (range: 7-42) days. Eight patients could not receive chemotherapy due to rapid progressive disease (n = 4), underlying treatment unrelated comorbidities (n = 2), and withdrawal of consent due to personal reasons (n = 2).

CONCLUSIONS

Treatment of SIRT followed by standard gemcitabine and cisplatin chemotherapy is feasible and effective for unresectable ICC. Further studies are required to study the optimal sequence of SIRT and chemotherapy.

Clinical consensus statement: Selective internal radiation therapy with yttrium 90 resin microspheres for hepatocellular carcinoma in Asia

BACKGROUND

Hepatocellular carcinoma (HCC) is subject to different management approaches and guidelines according to Eastern and Western therapeutic algorithms. Use of selective internal radiation therapy (SIRT) with resin yttrium 90 microspheres for HCC has increased in Asia in recent years, without clearly defined indications for its optimal application. The objective of this systematic review and expert consensus statement is to provide guidance and perspectives on the use of SIRT among patients with HCC in Asia.

MATERIALS AND METHODS

A systematic literature review identified current publications on HCC management and SIRT recommendations. A group of 10 experts, representing stakeholder specialties and countries, convened between August 2020 and March 2021 and implemented a modified Delphi consensus approach to develop guidelines and indications for use of SIRT for HCC in Asia. Final recommendations were organized and adjudicated based on the level of evidence and strength of recommendation, per approaches outlined by the American College of Cardiology/American Heart Association and Oxford Centre for Evidence-Based Medicine.

RESULTS

The experts acknowledged a general lack of evidence relating to use of SIRT in Asia and identified as an unmet need the lack of phase 3 randomized trials comparing clinical outcomes and survival following SIRT versus other therapies for HCC. Through an iterative process, the expert group explored areas of clinical relevance and generated 31 guidance statements and a patient management algorithm that achieved consensus.

CONCLUSION

These recommendations aim to support clinicians in their decision-making and to help them identify and treat patients with HCC using SIRT in Asia. The recommendations also highlight areas in which further clinical trials are needed to define the role of SIRT in management of HCC among Asian populations.

A global evaluation of advanced dosimetry in transarterial radioembolization of hepatocellular carcinoma with Yttrium-90: the TARGET study

PURPOSE

To investigate the relationships between tumor absorbed dose (TAD) or normal tissue absorbed dose (NTAD) and clinical outcomes in hepatocellular carcinoma (HCC) treated with yttrium-90 glass microspheres.

METHODS

TARGET was a retrospective investigation in 13 centers across eight countries. Key inclusion criteria: liver-dominant HCC with or without portal vein thrombosis, < 10 tumors per lobe (at least one ≥ 3 cm), Child-Pugh stage A/B7, BCLC stages A-C, and no prior intra-arterial treatment. Multi-compartment pre-treatment dosimetry was performed retrospectively. Primary endpoint was the relationship between ≥ grade 3 hyperbilirubinemia (such that > 15% of patients experienced an event) without disease progression and NTAD. Secondary endpoints included relationships between (1) objective response (OR) and TAD, (2) overall survival (OS) and TAD, and (3) alpha fetoprotein (AFP) and TAD.

RESULTS

No relationship was found between NTAD and ≥ grade 3 hyperbilirubinemia, which occurred in 4.8% of the 209 patients. The mRECIST OR rate over all lesions was 61.7%; for the target (largest) lesion, 70.8%. Responders and non-responders had geometric mean total perfused TADs of 225.5 Gy and 188.3 Gy (p = 0.048). Probability of OR was higher with increasing TAD (p = 0.044). Higher TAD was associated with longer OS (HR per 100 Gy increase = 0.83, 95% CI: 0.71-0.95; p = 0.009). Increased TAD was associated with higher probability of AFP response (p = 0.046 for baseline AFP ≥ 200 ng/mL).

CONCLUSION

Real-world data confirmed a significant association between TAD and OR, TAD and OS, and TAD and AFP response. No association was found between ≥ grade 3 hyperbilirubinemia and NTAD.

TRIAL REGISTRATION NUMBER

NCT03295006.

EANM procedure guideline for the treatment of liver cancer and liver metastases with intra-arterial radioactive compounds

Primary liver tumours (i.e. hepatocellular carcinoma (HCC) or intrahepatic cholangiocarcinoma (ICC)) are among the most frequent cancers worldwide. However, only 10-20% of patients are amenable to curative treatment, such as resection or transplant. Liver metastases are most frequently caused by colorectal cancer, which accounts for the second most cancer-related deaths in Europe. In both primary and secondary tumours, radioembolization has been shown to be a safe and effective treatment option. The vast potential of personalized dosimetry has also been shown, resulting in markedly increased response rates and overall survival. In a rapidly evolving therapeutic landscape, the role of radioembolization will be subject to changes. Therefore, the decision for radioembolization should be taken by a multidisciplinary tumour board in accordance with the current clinical guidelines. The purpose of this procedure guideline is to assist the nuclear medicine physician in treating and managing patients undergoing radioembolization treatment. PREAMBLE: The European Association of Nuclear Medicine (EANM) is a professional non-profit medical association that facilitates communication worldwide among individuals pursuing clinical and research excellence in nuclear medicine. The EANM was founded in 1985. These guidelines are intended to assist practitioners in providing appropriate nuclear medicine care for patients. They are not inflexible rules or requirements of practice and are not intended, nor should they be used, to establish a legal standard of care. The ultimate judgment regarding the propriety of any specific procedure or course of action must be made by medical professionals taking into account the unique circumstances of each case. Thus, there is no implication that an approach differing from the guidelines, standing alone, is below the standard of care. To the contrary, a conscientious practitioner may responsibly adopt a course of action different from that set out in the guidelines when, in the reasonable judgment of the practitioner, such course of action is indicated by the condition of the patient, limitations of available resources or advances in knowledge or technology subsequent to publication of the guidelines. The practice of medicine involves not only the science but also the art of dealing with the prevention, diagnosis, alleviation and treatment of disease. The variety and complexity of human conditions make it impossible to always reach the most appropriate diagnosis or to predict with certainty a particular response to treatment. Therefore, it should be recognised that adherence to these guidelines will not ensure an accurate diagnosis or a successful outcome. All that should be expected is that the practitioner will follow a reasonable course of action based on current knowledge, available resources and the needs of the patient to deliver effective and safe medical care. The sole purpose of these guidelines is to assist practitioners in achieving this objective.

90Y Radioembolization versus Drug-eluting Bead Chemoembolization for Unresectable Hepatocellular Carcinoma: Results from the TRACE Phase II Randomized Controlled Trial

Background Transarterial chemoembolization (TACE) is the recommended treatment for intermediate hepatocellular carcinoma (HCC) according to the Barcelona Clinic Liver Cancer guidelines. Prospective uncontrolled studies suggest that yttrium 90 (⁹⁰Y) transarterial radioembolization (TARE) is a safe and effective alternative. Purpose To compare the efficacy and safety of TARE with TACE for unresectable HCC. Materials and Methods In this single-center prospective randomized controlled trial (TRACE), ⁹⁰Y glass TARE was compared with doxorubicin drug-eluting bead (DEB) TACE in participants with intermediate-stage HCC, extended to Eastern Cooperative Oncology Group performance status 1 and those with early-stage HCC not eligible for surgery or thermoablation. Participants were recruited between September 2011 and March 2018. The primary end point was time to overall tumor progression (TTP) (Kaplan-Meier analysis) in the intention-to-treat (ITT) and per-protocol (PP) groups. Results At interim analysis, 38 participants (median age, 67 years; IQR, 63-72 years; 33 men) were randomized to the TARE arm and 34 (median age, 68 years; IQR, 61-71 years; 30 men) to the DEB-TACE arm (ITT group). Median TTP was 17.1 months in the TARE arm versus 9.5 months in the DEB-TACE arm (ITT group hazard ratio [HR], 0.36; 95% CI: 0.18, 0.70; P = .002) (PP group, 32 and 34 participants, respectively, in each arm; HR, 0.29; 95% CI: 0.14, 0.60; P < .001). Median overall survival was 30.2 months after TARE and 15.6 months after DEB-TACE (ITT group HR, 0.48; 95% CI: 0.28, 0.82; P = .006). Serious adverse events grade 3 or higher (13 of 33 participants [39%] vs 19 of 36 [53%] after TARE and DEB-TACE, respectively; P = .47) and 30-day mortality (0 of 33 participants [0%] vs three of 36 [8.3%]; P = .24) were similar in the safety groups. At the interim, the HR for the primary end point, TTP, was less than 0.39, meeting the criteria to halt the study. Conclusion With similar safety profile, yttrium 90 radioembolization conferred superior tumor control and survival compared with chemoembolization using drug-eluting beads in selected participants with early or intermediate hepatocellular carcinoma. Clinical trial registration no. NCT01381211 © RSNA, 2022 Online supplemental material is available for this article.

TARE in Hepatocellular Carcinoma: From the Right to the Left of BCLC

The Barcelona Clinic Liver Cancer (BCLC) system is the most commonly used staging system for hepatocellular carcinoma (HCC) in Western countries. BCLC aims to categorize patients into five stages with different prognoses and to allocate treatment according to these stages based on the best possible contemporary evidence. Transarterial radioembolization (TARE) has recently entered at the left of the BCLC algorithm (i.e., BCLC 0-A), mainly because of negative phase III trials in BCLC C stage. TARE has shown a steady increase in nationwide studies over the past 20 years and has even been adopted in some tertiary centers as the primary HCC treatment across all BCLC stages. We aimed to review the history of TARE in HCC, starting from advanced HCC and gradually expanding to earlier stages at the left of the BCLC system.

Incidental Finding of Pulmonary Embolism at Workup Before SIRT

ABSTRACT

Selective internal radiation therapy (SIRT) is a catheter-guided treatment offered to selected patients with primary and secondary liver malignancies. SIRT is preceded by a workup procedure, where 99mTc-MAA (macroaggregated albumin) is injected in the tumor supplying artery/arteries followed by MAA scintigraphy. SIRT is frequently offered to patients with hepatocellular carcinoma (HCC), but large HCCs are known to be associated with a high risk of liver-to-lung shunting. We present a HCC patient case where a large lung-shunt enabled diagnosis of pulmonary embolism.

Dynamic Lymphocyte Changes Following Transarterial Radioembolization: Association with Normal Liver Dose and Effect on Overall Survival

Objective

To evaluate the dynamic changes of lymphocytes following transarterial radioembolization (TARE) for hepatocellular carcinoma (HCC) and their relationship to normal liver dose (NLD).

Materials and Methods

A total of 93 patients who underwent 102 treatments were retrospectively reviewed. Absolute lymphocyte counts pretreatment and at 1, 3, 6, and 12 months were evaluated. Kaplan–Meier, Spearman correlation, receiver operating characteristic (ROC) curve, and area under the curve (AUC) analyses were performed.

Results

The mean absolute lymphocyte count at baseline was 1.25 ± 0.79 10³/µL which was significantly greater than 1 (0.71 ± 0.47 10³/µL, p<0.0001), 3 (0.79 ± 0.77 10³/µL, p=0.0003), and 6 (0.81 ± 0.44 10³/µL, p=0.0001) months, but not significantly different than 12 (0.92 ± 0.8 10³/µL, p=0.12) months post treatment. There was a modest negative correlation between NLD and lymphocyte count at 1 month (rho= −0.216, p=0.03), which strengthened at 3 months post treatment (rho= −0.342, p=0.008). AUC of ROC analysis between absolute lymphocyte count ≤1 10³/µL or >1 10³/µL at 1, 3, 6, and 12 months post treatment was 0.625, 0.676, 0.560, and 0.794, respectively. Univariate analysis of overall survival when separating patients by a lymphocyte count of ≤1 10³/µL and >1 10³/µL demonstrated a significant difference at 1 (HR: 0.56, 95% CI: 0.33–0.95, p=0.03), 3 (HR: 0.41, 95% CI: 0.18–0.94, p=0.035) and 6 (HR: 0.36, 95% CI: 0.17–0.77, p=0.008) months post treatment, but not pretreatment or at 12 months.

Conclusion

NLD may correlate with lymphocyte depression at 1 and 3 months and lymphopenia may portend a worse overall survival in the post treatment setting.

Realized tumor to normal ratios in hepatocellular carcinoma patients undergoing transarterial radioembolization: a retrospective evaluation

OBJECTIVES

To determine the realized tumor to normal ratios (TNRs) in patients undergoing radiation segmentectomies (RS); determine the relationship between TNRs and particle load in transarterial radioembolization (TARE).

METHODS

In total, 148 patients who underwent 184 TARE procedures for hepatocellular carcinoma were evaluated. Post treatment SPECT CT bremsstrahlung imaging was analyzed utilizing Simplicit90y™ to determine realized TNR. A model which normalized activity across all RS treatments to a level that would achieve 400 Gy by unicompartmental dosing was created to determine the affect realized TNR would have on tumor absorbed dose.

RESULTS

The mean TNR in the setting of RS was 2.88 ± 1.60 and was higher for glass as compared to resin microspheres (3.07 ± 1.68 vs 2.24 ± 1.21, p = 0.01). The TNR was significantly greater in the RS as compared to the lobar deliveries (2.88 ± 1.60 vs 2.16 ± 1.12, p < 0.01). When normalizing the activity of RS treatments to the level required to achieve 400 Gy by unicompartmental calculations, there was found to be significant differences in the predicted tumor absorbed dose when separated by the median tumor dose (601.2 ± 133.3 vs 1146.9 ± 297.5, p < 0.01) or median realized TNR (1119.2 ± 341 Gy vs 635.7 ± 160.2 Gy, p < 0.01). Particle load was found to be associated with TNR on univariate (p < 0.01) and multivariate (p < 0.01) analysis.

CONCLUSION

Significant TNRs are seen in RS and perhaps argue for the use of multi-compartmental dosimetry techniques in this setting and particle load may affect TNR.

KEY POINTS

• Tumor to normal ratios were significantly higher in radiation segmentectomies than lobar deliveries. • Tumor to normal ratios were significantly higher when utilizing glass, as compared to resin microspheres. • When creating a model that prescribed the activity required to reach 400 Gy by MIRD, realized tumor dose varied significantly in radiation segmentectomies.

Dosimetry of nuclear medicine therapies: current controversies and impact on treatment optimization

Nuclear medicine therapeutic procedures have considerably expanded over the last few years, and their number is expected to grow exponentially in the future. Internal dosimetry has significantly developed as well, but has not yet been uniformly accepted as a valuable tool for prediction of therapeutic efficacy and toxicity. In this paper, we briefly summarize some of the arguments about the implementation of internal dosimetry in clinical practice. In addition, we provide a few examples of radionuclide anticancer therapies for which internal dosimetry demonstrated a significant impact on treatment optimization and patient outcome.

Beyond the MAA-Y90 Paradigm: The Evolution of Radioembolization Dosimetry Approaches and Scout Particles

Radioembolization is a well-established treatment for primary and metastatic liver cancer. There is increasing interest in personalized treatment planning supported by dosimetry, as it provides an opportunity to optimize dose delivery to tumor and minimize nontarget deposition, which demonstrably increases the efficacy and safety of this therapy. However, the optimal dosimetry procedure in the radioembolization setting is still evolving; existing data are limited as few trials have prospectively tailored dose based on personalized planning and predominantly semi-empirical methods are used for dose calculation. Since the pretreatment or "scout" procedure forms the basis of dosimetry calculations, an accurate and reliable technique is essential. ^99m Tc-MAA SPECT constitutes the current accepted standard for pretreatment imaging; however, inconsistent patterns in published data raise the question whether this is the optimal agent. Alternative particles are now being introduced to the market, and early indications suggest use of an identical scout and treatment particle may be superior to the current standard. This review will undertake an evaluation of the increasingly refined dosimetric methods driving radioembolization practices, and a horizon scanning exercise identifying alternative scout particle solutions. Together these constitute a compelling vision for future treatment planning methods that prioritize individualized care.

Key Role of Personalized Dosimetry in Dose Adjustment for Selective Internal Radiotherapy: Retrospective Study of Patients Treated With 90Y Resin Microspheres

PURPOSE

Selective internal radiotherapy with 90Y microspheres is widely used for the treatment of patients with liver cancer. A dosimetric analysis using the dosimetry software Simplicit90y (Boston Scientific, Natick, MA) was conducted to define doses to the tumor and healthy liver, and to determine a threshold tumor dose that could predict progression-free survival.

METHODS

Patients experiencing hepatocellular carcinoma and treated with 90Y-labeled resin microspheres were included in a retrospective study. The time-to-progression of the target lesions (TTPLs) and overall survival (OS) were evaluated using Kaplan-Meier tests, and this comparison was based on a log-rank test.

RESULTS

Twenty-four procedures for patients with portal vein thrombosis were realized. Median follow-up was 16 months. A threshold tumor dose of 125 Gy was determined with a sensitivity of 89% and a specificity of 100%. For patients with a tumor dose of less than 125 Gy, the median OS was 7.5 months (95% confidence interval [CI], 5-14 months) and the TTPL was 3 months (95% CI, 2-6 months) versus 33 months (95% CI, 22-39 months) and 23 months (95% CI, 7-38 months), respectively, for those with a tumor dose of 125 Gy or more (P = 0.002 and P = 0.0004).

CONCLUSIONS

Personalized dosimetry based on 99mTc-MAA SPECT/CT is predictive of TTPL and OS in patients with hepatocellular carcinoma. Customized dosimetry software is essential to optimize treatment planning.