Recommendations for radioembolization of hepatic malignancies using yttrium-90 microsphere brachytherapy: a consensus panel report from the radioembolization brachytherapy oncology consortium

Stereotactic Body Radiation Therapy: A New Strategy for Loco-Regional Treatment for Hepatocellular Carcinoma While Awaiting Liver Transplantation

BACKGROUND

Trans-arterial chemoembolization and radiofrequency ablation are commonly used for control of hepatocellular carcinoma (HCC) on liver transplant (LTx) waiting list. Stereotactic body radiation therapy (SBRT) was introduced to our institution for HCC as a bridging or downsizing therapy to LTx.

PATIENTS AND METHODS

Twenty-five HCC lesions in 22 patients were treated with SBRT while waiting for LTx from January 2010 to December 2015. Nineteen of these patients received deceased donor LTx. SBRT was defined as 40-50 Gy delivered in 4-6 fractions. Pre- and post-liver transplant outcome were analyzed in addition to the dropout rate and tumor response to SBRT.

RESULTS

Median size of original tumors was 3.2 cm (2.0-8.9), and median size of tumor after SBRT was significantly smaller at 0.9 cm (0-3.2) in the explanted livers (p < 0.01). The dropout rate was 9%, and they were only downsized patients outside of Milan criteria. Liver disease did not progress between pre- and post-SBRT except one patient. Twenty-eight percent of treated HCCs showed complete pathologic response, and 22% had extensive partial response with some residual tumor. No HCC recurrence was experienced after LTx.

CONCLUSION

SBRT is indicated to be safe, effective treatment for HCC on LTx waiting list, and it leads to satisfactory post-liver transplant outcomes.

Red Flags, Pitfalls, and Cautions in Y90 Radiotherapy

Radioembolization with yttrium-90 (Y90) microspheres is increasingly used to palliate patients with liver-dominant malignancy. With appropriate patient selection, this outpatient treatment is efficacious with limited toxicity profile. This article reviews common scenarios that can present in daily practice including evaluation of liver functions, evaluation of previous therapies, integrating Y90 into ongoing systemic therapy, determining performance status, and considering retreatment for patients who have already undergone Y90 who have hepatic dominant progression. Finally, we address the importance of evaluating tumors in potential watershed zones to maximize treatment response by using c-arm computed tomography. Many of these potential variables can overlap in an individual patient. By considering these factors individually, the consulting Interventional Radiologist can present a thorough treatment plan with a full description of expected outcomes and toxicities to clinic patients.

90 Y SPECT/CT quantitative study and comparison of uptake with pretreatment 99 m Tc-MAA SPECT/CT in radiomicrosphere therapy

INTRODUCTION

Yttrium-90 (90 Y) microsphere post-treatment imaging reflects the true distribution characteristics of microspheres in the tumor and liver compartments. However, due to its decay spectra profile lacking a pronounced photopeak, the bremsstrahlung imaging for 90 Y has inherent limitations. The absorbed dose calculations for 90 Y microspheres radiomicrosphere therapy (RMT) sustain a limitation due to the poor quality of 90 Y imaging. The aim of this study was to develop quantitative methods to improve the post-treatment 90 Y bremsstrahlung single photon emission tomography (SPECT)/computed tomography (CT) image analysis for dosimetric purposes and to perform a quantitative comparison with the 99m Tc-MAA SPECT/CT images, which is used for theranostics purposes for liver and tumor dosimetry.

METHODS

Pre and post-treatment SPECT/CT data of patients who underwent RMT for primary or metastatic liver cancer were acquired. A Jasczak phantom with eight spherical inserts of various sizes was used to obtain optimal iteration number for the contrast recovery algorithm for improving 90 Y bremsstrahlung SPECT/CT images. Comparison of uptake on 99m Tc-MAA and 90 Y microsphere SPECT/CT images was assessed using tumor to healthy liver ratios (TLRs). The voxel dosimetry technique was used to estimate absorbed doses. Absorbed doses within the tumor and healthy part of the liver were also investigated for correlation with administered activity.

RESULTS

Improvement in CNR and contrast recovery coefficients on patient and phantom 90 Y bremsstrahlung SPECT/CT images respectively were achieved. The 99m Tc-MAA and 90 Y microspheres SPECT/CT images showed significant uptake correlation (r = 0.9, P = 0.05) with mean TLR of 9.4 ± 9.2 and 5.0 ± 2.2, respectively. The correlation between the administered activity and tumor absorbed dose was weak (r = 0.5, P > 0.05), however, healthy liver absorbed dose increased with administered activity (r = 0.8, P = 0.0).

CONCLUSIONS

This study demonstrated correlation in mean TLR between 99m Tc-MAA and 90 Y microsphere SPECT/CT.

Dosimetry of Y-90 Microspheres Utilizing Tc-99m SPECT and Y-90 PET

Dosimetry for yttrium-90 radioembolization continues to generate interest and controversy, as multiple approaches have been used effectively. Traditionally, simple formulas primarily based on patients' body weight or perfused liver volume were used. Over the past several years, dosimetry refinements have led to marked improvements in this therapy from both a safety and efficacy standpoint. Technetium-99m macroaggregated albumin single photon emission computed tomography (SPECT) optimizes pretreatment dosimetry to ensure delivery of a therapeutic radiation dose to the tumor while minimizing nontarget radiation to healthy hepatic tissue. Post-treatment yttrium-90 PET utilizing the inherent internal pair production of yttrium-90 accurately calculates the absorbed dose to tumors and to the normal hepatic parenchyma, which correlates with patient outcomes. As dosimetric calculations become more complex, quantitative imaging with Tc-99m SPECT and Y-90 PET may set the new standard for radioembolization dosimetry.

Radioembolization of Hepatocellular Carcinoma with Built-In Dosimetry: First in vivo Results with Uniformly-Sized, Biodegradable Microspheres Labeled with 188Re

A common form of treatment for patients with hepatocellular carcinoma (HCC) is transarterial radioembolization (TARE) with non-degradable glass or resin microspheres (MS) labeled with ⁹⁰Y (⁹⁰Y-MS). To further simplify the dosimetry calculations in the clinical setting, to have more control over the particle size and to change the permanent embolization to a temporary one, we developed uniformly-sized, biodegradable ¹⁸⁸Re-labeled MS (¹⁸⁸Re-MS) as a new and easily imageable TARE agent.

Methods: MS made of poly(L-lactic acid) were produced in a flow focusing microchip. The MS were labeled with ¹⁸⁸Re using a customized kit. An orthotopic HCC animal model was developed in male Sprague Dawley rats by injecting N1-S1 cells directly into the liver using ultrasound guidance. A suspension of ¹⁸⁸Re-MS was administered via hepatic intra-arterial catheterization 2 weeks post-inoculation of the N1-S1 cells. The rats were imaged by SPECT 1, 24, 48, and 72 h post-radioembolization.

Results: The spherical ¹⁸⁸Re-MS had a diameter of 41.8 ± 6.0 µm (CV = 14.5%). The site and the depth of the injection of N1-S1 cells were controlled by visualization of the liver in sonograms. Single 0.5 g tumors were grown in all rats. ¹⁸⁸Re-MS accumulated in the liver with no deposition in the lungs. ¹⁸⁸Re decays to stable ¹⁸⁸Os by emission of β^¯ particles with similar energy to those emitted by ⁹⁰Y while simultaneously emitting γ photons, which were imaged directly by single photon computed tomography (SPECT). Using Monte Carlo methods, the dose to the tumors was calculated to be 3-6 times larger than to the healthy liver tissue.

Conclusions:¹⁸⁸Re-MS have the potential to become the next generation of β^¯-emitting MS for TARE. Future work revolves around the investigation of the therapeutic potential of ¹⁸⁸Re-MS in a large-scale, long-term preclinical study as well as the evaluation of the clinical outcomes of using ¹⁸⁸Re-MS with different sizes, from 20 to 50 µm.

Sorafenib Reduced Significantly Heptopulmonary Shunt in a Large Hepatocelullar Carcinoma

An 81-year-old man with a large hepatocellular carcinoma was referred in our institution for Y radioembolization (RE). The preliminary arteriography using Tc-macroaggregate albumin demonstrated an important hepatopulmonary shunt. It was an exclusion criterion for RE due to high risks of lung radiations. Then, the patient was treated with sorafenib during 4 months, stopped because of grade 3 toxicity. A second liver arteriography was performed, and Tc-macroaggregate albumin imaging showed an important reduction of the lung shunt. Transient therapy with sorafenib permitted to close the lung shunt and was a bridge for RE.

Holmium-166 Radioembolization in Hepatocellular Carcinoma: Feasibility and Safety of a New Treatment Option in Clinical Practice

PURPOSE

To investigate clinical feasibility, technical success and toxicity of ¹⁶⁶Ho-radioembolization (¹⁶⁶Ho-RE) as new approach for treatment of hepatocellular carcinomas (HCC) and to assess postinterventional calculation of exact dosimetry through quantitative analysis of MR images.

MATERIALS AND METHODS

From March 2017 to April 2018, nine patients suffering from HCC were treated with ¹⁶⁶Ho-RE. To calculate mean doses on healthy liver/tumor tissue, MR was performed within the first day after treatment. For evaluation of hepatotoxicity and to rule out radioembolization-induced liver disease (REILD), the Model for End-Stage Liver Disease (MELD) Score, the Common Terminology Criteria for Adverse Events and specific laboratory parameters were used 1-day pre- and posttreatment and after 60 days. After 6 months, MR/CT follow-up was performed.

RESULTS

In five patients the right liver lobe, in one patient the left liver lobe and in three patients both liver lobes were treated. Median administered activity was 3.7 GBq (range 1.7-5.9 GBq). Median dose on healthy liver tissue was 41 Gy (21-55 Gy) and on tumor tissue 112 Gy (61-172 Gy). Four patients suffered from mild postradioembolization syndrome. No significant differences in median MELD-Score were observed pre-, posttherapeutic and 60 days after ¹⁶⁶Ho-RE. No deterioration of liver function and no indicators of REILD were observed. One patient showed a complete response, four a partial response, three a stable disease and one a progressive disease at the 6 months follow-up.

CONCLUSION

¹⁶⁶Ho-RE seems to be a feasible and safe treatment option with no significant hepatotoxicity for treatment of HCC.

SIR-Spheres® Y-90 resin microspheres in chemotherapy refractory or intolerant patients with metastatic colorectal cancer

Selective internal radiation therapy is a form of intra-arterial brachytherapy used to treat primary liver cancer and liver metastases. This article aims to provide an overview of the clinical, economic, organizational legal, social and ethical impact of selective internal radiation therapy using SIR-Spheres Y-90 resin microspheres in the treatment of patients with unresectable, liver-dominant metastatic colorectal cancer who are refractory to or intolerant of chemotherapy. A systematic literature review was performed by querying PubMed, Scopus, EBSCO, CRD and GIN. Two reviewers blindly screened the records retrieved against predefined inclusion/exclusion criteria. The selected studies where summarized following a simplified version of the EuNetHTA Core Model® 2.1. The studies included evaluated selective internal radiation therapy in first-line or further-line treatment and showed a good safety and tolerability profile and significant improvement in efficacy expressed as time to liver progression, progression-free survival and overall survival. Selective internal radiation therapy should be provided in specialized centres and administered by a multidisciplinary team. A hub-and-spoke network could be a viable option to guarantee access to this technology across jurisdictions. The lack of a specific diagnosis-related group tariff accounting for the cost of the device could be seen as the major obstacle to a fair diffusion of this technology. The economic evaluations currently available show the cost-effectiveness of this technology in the population under study. Selective internal radiation therapy using SIR-Spheres Y-90 resin microspheres appears to be a clinically effective and cost-effective option in the treatment of metastatic colorectal cancer patients who are chemotherapy refractory or chemotherapy intolerant.

90Y TOF-PET based EUD reunifies patient survival prediction in resin and glass microspheres radioembolization of HCC tumours

Clinical studies reported a twofold ratio between the efficacies per Gy of resin versus glass spheres. Our aim is to investigate whether this difference could result from the different degrees of heterogeneity in sphere distribution between the two medical devices. The ⁹⁰Y TOF-PET based equivalent uniform doses (EUD) was used for this purpose. 58 consecutive HCC radioembolizations were retrospectively analyzed. Absorbed doses D and Jones-Hoban EUD in lesions were computed. Radioembolization efficacy was assessed using Kaplan-Meier survival curves. In order to match together the glass and resin spheres survival curves using a 40 Gy-threshold, an efficacy factor of 0.73 and 0.36 has to be applied on their absorbed dose, respectively. Using EUD, a nice matching between glass and resin survival curves was obtained with a better separation of the responding and not responding survival curves. The results clearly support the fact that the activity heterogeneity observed in ⁹⁰Y TOF-PET post radioembolization does not only result from statistical noise, but also reflects the actual heterogeneity of the spheres distribution. Use of EUD reunifies the efficacy of the two medical devices.

In Patients We Trust: Reliability of Self-Reported Weight and Height in Nuclear Medicine Patients

The aim of the study was to assess the reliability of the self-reported weight and height of nuclear medicine patients in view of recommendations for weight-dependent tracer application for imaging and therapy. Methods: In total, 824 patients (334 men and 490 women) were asked to report their weight and height before imaging or therapy and their level of confidence. Subsequently, the weight and height of each patient were measured, and body mass index, body surface area, and lean body mass were calculated. Differences between reported and true values were compared for statistically significant differences. Results: The average patient age was 60 ± 14 y (range, 17-91 y). An over- or underestimation of weight by at least 10% was observed in 2% of patients, and height was overestimated by 1% by the patients. The BMI calculation was affected by incorrect self-reported values. Conclusion: Most self-reported weights and heights of nuclear medicine patients are accurate. However, since over- and underestimation of weight and height lead to incorrect body mass index, body surface area, and lean body mass values, patient weights should be measured at least for patients receiving a weight-adapted therapy or if quantification in PET/CT is needed.

Analysis of a National Programme for Selective Internal Radiation Therapy for Colorectal Cancer Liver Metastases

AIMS

Patients with chemotherapy-refractory colorectal cancer liver metastases have limited therapeutic options. Selective internal radiation therapy (SIRT) delivers yttrium 90 microspheres as a minimally invasive procedure. This prospective, single-arm, observational, service-evaluation study was part of National Health Service England Commissioning through Evaluation.

METHODS

Patients eligible for treatment had histologically confirmed carcinoma with liver-only/liver-dominant metastases with clinical progression during or following oxaliplatin-based and irinotecan-based chemotherapy. All patients received SIRT plus standard of care. The primary outcome was overall survival; secondary outcomes included safety, progression-free survival (PFS) and liver-specific PFS (LPFS).

RESULTS

Between December 2013 and March 2017, 399 patients were treated in 10 centres with a median follow-up of 14.3 months (95% confidence interval 9.2-19.4). The median overall survival was 7.6 months (95% confidence interval 6.9-8.3). The median PFS and LPFS were 3.0 months (95% confidence interval 2.8-3.1) and 3.7 months (95% confidence interval 3.2-4.3), respectively. During the follow-up period, 143 patients experienced an adverse event and 8% of the events were grade 3.

CONCLUSION

Survival estimates from this pragmatic study show clinical outcomes attainable in the National Health Service comparable with previously published data. This study shows the value of a registry-based commissioning model to aid national commissioning decisions for highly specialist cancer treatments.

Factors Affecting Oncologic Outcomes of 90Y Radioembolization of Heavily Pre-Treated Patients With Colon Cancer Liver Metastases

INTRODUCTION

The purpose of this study was to identify predictors of overall (OS) and liver progression-free survival (LPFS) following Yttrium-90 radioembolization (RAE) of heavily pretreated patients with colorectal cancer liver metastases (CLM), as well as to create and validate a predictive nomogram for OS.

MATERIALS AND METHODS

Metabolic, anatomic, laboratory, pathologic, genetic, primary disease, and procedure-related factors, as well as pre- and post-RAE therapies in 103 patients with CLM treated with RAE from September 15, 2009 to March 21, 2017 were analyzed. LPFS was defined by Response Evaluation Criteria In Solid Tumors 1.1 and European Organization for Research and Treatment of Cancer criteria. Prognosticators of OS and LPFS were selected using univariate Cox regression, adjusted for clustering and competing risk analysis (for LPFS), and subsequently tested in multivariate analysis (MVA). The nomogram was built using R statistical software and internally validated using bootstrap resampling.

RESULTS

Patients received RAE at a median of 30.9 months (range, 3.4-161.7 months) after detection of CLM. The median OS and LPFS were 11.3 months (95% confidence interval, 7.9-15.1 months) and 4 months (95% confidence interval, 3.3-4.8 months), respectively. Of the 40 parameters tested, 6 were independently associated with OS in MVA. These baseline parameters included number of extrahepatic disease sites (P < .001), carcinoembryonic antigen (P < .001), albumin (P = .005), alanine aminotransferase level (P < .001), tumor differentiation level (P < .001), and the sum of the 2 largest tumor diameters (P < .001). The 1-year OS of patients with total points of < 25 versus > 80 was 90% and 10%, respectively. Bootstrap resampling showed good discrimination (optimism corrected c-index = 0.745) and calibration (mean absolute prediction error = 0.299) of the nomogram. Only baseline maximum standardized uptake value was significant in MVA for LPFS prediction (P < .001; SHR = 1.06).

CONCLUSION

The developed nomogram included 6 pre-RAE parameters and provided good prediction of survival post-RAE in heavily pretreated patients. Baseline maximum standardized uptake value was the single significant predictor of LPFS.

Intra-Arterial TheraSphere Yttrium-90 Glass Microspheres in the Treatment of Patients With Unresectable Hepatocellular Carcinoma: Protocol for the STOP-HCC Phase 3 Randomized Controlled Trial

BACKGROUND

Globally, hepatocellular carcinoma is the second most common cause of cancer deaths. It remains challenging to intensify cancer treatment without impairing liver function.

OBJECTIVE

The objective of the TheraSphere in the Treatment of Patients with Unresectable Hepatocellular Carcinoma (STOP-HCC) study is to examine the hypothesis that transarterial radioembolization (TheraSphere yttrium-90 glass microspheres) combined with standard first-line treatment with sorafenib will improve outcomes over treatment with sorafenib alone in unresectable hepatocellular carcinoma. The STOP-HCC study is the largest international, multicenter, prospective study of intra-arterial treatment in combination with sorafenib in unresectable hepatocellular carcinoma. Here we report the study design.

METHODS

STOP-HCC is a prospective, phase 3, open-label, randomized controlled study conducted across up to 105 sites in North America, Europe, and Asia. Eligible adults have unresectable hepatocellular carcinoma and a life expectancy of at least 12 weeks, 1 or more unidimensional measurable lesions, Child-Pugh score 7 points or less, and Eastern Cooperative Oncology Group Performance Status score 1 or lower, and are candidates for treatment with sorafenib. Presence of branch portal vein tumor thrombosis is permitted. Patients were randomly assigned in a 1:1 ratio to receive either sorafenib alone or transarterial radioembolization followed by sorafenib within 2 to 6 weeks. The primary outcome is overall survival. Secondary outcomes are time to progression, time to untreatable progression, time to symptomatic progression, tumor response, quality of life, and adverse event occurrence. The study is an adaptive trial, comprising a group-sequential design with 2 interim analyses with 520 patients, and an option to increase the sample size to 700 patients at the second interim analysis. The sample size of 520 patients allows for 417 deaths to give 80% power to detect an increase in median overall survival from 10.7 months for the sorafenib group (based on the Sorafenib Hepatocellular Carcinoma Assessment Randomized Protocol [SHARP] trial) to 14.2 months for the transarterial radioembolization+sorafenib group (hazard ratio 0.754) with 2-sided alpha of .05. The increased sample size of 700 patients allows for 564 deaths to give 80% power to detect a smaller difference in median overall survival from 10.7 months for the sorafenib group to 13.7 months for the transarterial radioembolization+sorafenib group (hazard ratio 0.781).

RESULTS

Enrollment for the study completed in September 2017. Results of the first and second interim analyses were reviewed by the Independent Data Monitoring Committee. The recommendation of the committee, at both interim analyses, was to continue the study without any changes.

CONCLUSIONS

The STOP-HCC study will contribute toward the establishment of the role of combination therapy with transarterial radioembolization and sorafenib in the treatment of unresectable hepatocellular carcinoma with and without branch portal vein tumor thrombosis.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01556490; https://clinicaltrials.gov/ct2/show/NCT01556490 (Archived by WebCite at http://www.webcitation.org/7188iygKs).

REGISTERED REPORT IDENTIFIER

RR1-10.2196/11234.

Predictors of Survival after Yttrium-90 Radioembolization for Colorectal Cancer Liver Metastases

PURPOSE

To identify clinical parameters that are prognostic for improved overall survival (OS) after yttrium-90 radioembolization (RE) in patients with liver metastases from colorectal cancer (CRC).

MATERIALS AND METHODS

A total of 131 patients who underwent RE for liver metastases from CRC, treated at 2 academic centers, were reviewed. Twenty-one baseline pretreatment clinical factors were analyzed in relation to OS by the Kaplan-Meier method along with log-rank tests and univariate and multivariate Cox regression analyses.

RESULTS

The median OS from first RE procedure was 10.7 months (95% confidence interval [CI], 9.4-12.7 months). Several pretreatment factors, including lower carcinoembryonic antigen (CEA; ≤20 ng/mL), lower aspartate transaminase (AST; ≤40 IU/L), neutrophil-lymphocyte ratio (NLR) <5, and absence of extrahepatic disease at baseline were associated with significantly improved OS after RE, compared with high CEA (>20 ng/mL), high AST (>40 IU/L), NLR ≥5, and extrahepatic metastases (P values of <.001, <.001, .0001, and .04, respectively). On multivariate analysis, higher CEA, higher AST, NLR ≥5, extrahepatic disease, and larger volume of liver metastases remained independently associated with risk of death (hazard ratios of 1.63, 2.06, 2.22, 1.48, and 1.02, respectively).

CONCLUSIONS

The prognosis of patients with metastases from CRC is impacted by a complex set of clinical parameters. This analysis of pretreatment factors identified lower AST, lower CEA, lower NLR, and lower tumor burden (intra- or extrahepatic) to be independently associated with higher survival after hepatic RE. Optimal selection of patients with CRC liver metastases may improve survival rates after administration of yttrium-90.

Comparison of Cone-Beam Tomography and Cross-Sectional Imaging for Volumetric and Dosimetric Calculations in Resin Yttrium-90 Radioembolization

PURPOSE

To compare the use of cone-beam computed tomography versus contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI) in the calculation of liver volume and planned dose for yttrium-90 radioembolization.

MATERIALS AND METHODS

The study retrospectively assessed 47 consecutive patients who underwent resin Y-90 radioembolization consecutively over a 2-year period at a single center. Volume calculation software was used to determine perfused lobar liver volumes from cone-beam CT (CBCT) images obtained during mapping angiography. CBCT-derived volumes were compared with perfused lobar volume derived from contrast-enhanced CT and MRI. Nominal activities as determined by the SIR-Spheres Microspheres Activity Calculator were similarly calculated and compared using both CBCT and conventionally acquired volumes.

RESULTS

A total of 82 hepatic lobes were assessed in 47 patients. The mean percentage difference between combined CT-MRI- and CBCT-derived calculated lobar volumes was 25.3% (p = 0.994). The mean percentage difference in calculated dose between the two methods was 21.8 ± 24.6% (p = 0.42). Combined left and right lobar CT-derived dose difference was less than 10% in 22 lobes, between 10 and 25% in 20 lobes, between 25 and 50% in 13 lobes and greater than 50% in 5 lobes. Combined left and right lobar MRI-derived dose difference was less than 10% in 11 lobes, between 10 and 25% in 7 lobes, between 25 and 50% in 2 lobes and greater than 50% in 1 lobe.

CONCLUSIONS

Although volume measurements derived from CT/MRI did not differ significantly from those derived from CBCT, variability between the two methods led to large and unexpected differences in calculated dose.

The Predictive Value of SPECT/CT imaging in colorectal liver metastases response after 90Y-radioembolization

The aim of this study was to evaluate a modified method of calculating the ^99mTc/⁹⁰Y tumor-to-normal-liver uptake ratio (mT/N) based on SPECT/CT imaging, for use in predicting the overall response of colorectal liver tumors after radioembolization. A modified phantom-based method of tumor-to-normal-liver ratio calculation was proposed and assessed. In contrast to the traditional method based on data gathered from the whole tumor, gamma counts are collected only from a 2D region of interest delineated in the SPECT/CT section with the longest tumor diameter (as specified in RECIST 1.1). The modified tumor-to-normal-liver ratio (mT/N1) and ⁹⁰Y predicted tumor absorbed dose (PAD) were obtained based on ^99mTc-MAA SPECT/CT, and similarly the modified tumor-to-normal-liver ratio (mT/N2) and ⁹⁰Y actual tumor absorbed dose (AAD) were calculated after ⁹⁰Y-SPECT/CT. Tumor response was assessed on follow-up CTs. Using the newly proposed method, a total of 103 liver colorectal metastases in 21 patients who underwent radioembolization (between June 2009 and October 2015) were evaluated in pre-treatment CT scans and ^99mTc-MAA-SPECT/CT scans and compared with post-treatment ⁹⁰Y-SPECT/CT scans and follow-up CT scans. The results showed that the mT/N1 ratio (p = 0.012), PAD (p < 0.001) and AAD (p < 0.001) were predictors of tumor response after radioembolization. The time to progression was significantly lengthened for tumors with mT/N1 higher than 1.7 or PAD higher than 70 Gy. The risk of progression for tumors with mT/N1 lower than 1.7 or PAD below 70 Gy was significantly higher. The mT/N2 ratio had no significant correlation with treatment results.

SPECT/CT image-based dosimetry for Yttrium-90 radionuclide therapy: Application to treatment response

This work demonstrates the efficacy of voxel‐based ⁹⁰Y microsphere dosimetry utilizing post‐therapy SPECT/CT imaging and applies it to the prediction of treatment response for the management of patients with hepatocellular carcinoma (HCC). A ⁹⁰Y microsphere dosimetry navigator (RapidSphere) within a commercial platform (Velocity, Varian Medical Systems) was demonstrated for three microsphere cases that were imaged using optimized bremsstrahlung SPECT/CT. For each case, the ⁹⁰Y SPECT/CT was registered to follow‐up diagnostic MR/CT using deformable image registration. The voxel‐based dose distribution was computed using the local deposition method with known injected activity. The system allowed the visualization of the isodose distributions on any of the registered image datasets and the calculation of dose‐volume histograms (DVHs). The dosimetric analysis illustrated high local doses that are characteristic of blood‐flow directed brachytherapy. In the first case, the HCC mass demonstrated a complete response to treatment indicated by a necrotic region in follow‐up MR imaging. This result was dosimetrically predicted since the gross tumor volume (GTV) was well covered by the prescription isodose volume (V150 Gy = 85%). The second case illustrated a partial response to treatment which was characterized by incomplete necrosis of an HCC mass and a remaining area of solid enhancement in follow‐up MR imaging. This result was predicted by dosimetric analysis because the GTV demonstrated incomplete coverage by the prescription isodose volume (V470 Gy = 18%). The third case demonstrated extrahepatic activity. The dosimetry indicated that the prescription (125 Gy) isodose region extended outside of the liver into the duodenum (178 Gy maximum dose). This was predictive of toxicity as the patient later developed a duodenal ulcer. The ability to predict outcomes and complications using deformable image registration, calculated isodose distributions, and DVHs, points to the clinical utility of patient‐specific dose calculations for ⁹⁰Y radioembolization treatment planning.

Post Locoregional Therapy Treatment Imaging in Hepatocellular Carcinoma Patients: A Literature-based Review

Imaging plays a crucial role in the diagnosis of hepatocellular carcinoma (HCC) as well as in determining treatment efficacy, or complications, following therapy. Unlike other cancers, HCC is most commonly treated by locoregional therapies (LRTs) such as thermal ablation, transarterial chemoembolization, and transarterial radioembolization. These treatments can lead to changes on imaging that make determination of residual/recurrent disease difficult. This literature-based review discusses the expected postimaging findings following LRT.

Beyond the Knife: The Evolving Nonsurgical Management of Oligometastatic Colorectal Cancer

In patients with liver-limited oligometastatic disease, the goal of treatment can be curative intent. Historically, this was accomplished in patients presenting with upfront resectable disease. The availability of increasingly efficacious chemotherapy and biologic combinations with encouraging response rates led to the potential to convert unresectable disease to resectability. Beyond the backbone of surgery, we now have a portfolio of locoregional strategies to consider.From an interventional radiology perspective, the use of portal vein embolization can facilitate hypertrophy of the liver in anticipation of resection, thus converting unresectable disease to one amenable to a surgical approach with curative intent. Technological advances in liver-directed ablative therapies have afforded the possibility of eliminate radiographically evident disease with the hope for long-term disease control. Advanced radiotherapy techniques are further increasing the therapeutic options for patients with metastatic colorectal cancer. Improvements in external-beam radiotherapy over the past 2 decades include image-guided radiotherapy, intensity-modulated radiotherapy, stereotactic body radiotherapy, and proton-beam therapy. Finally, selective internal radiation therapy (SIRT) with microspheres labeled with the β-emitter ⁹⁰Y enable targeted delivery of radiation to hepatic tumors. A coordinated multidisciplinary approach is required to integrate these nonsurgical adjuncts in an evidence-based manner to optimize outcomes for patients with potentially resectable metastatic disease. In this article, we summarize recent developments in systemic therapy, radiotherapy, and interventional liver-directed therapies that have changed the treatment landscape for patients with oligometastatic colorectal cancer.

Diffusion-weighted MRI Is Superior to PET/CT in Predicting Survival of Patients Undergoing 90Y Radioembolization of Hepatic Metastases

Purpose To determine the relationship between diffusion-weighted (DW) liver MR images obtained 4-6 weeks after lobar yttrium 90 (⁹⁰Y) treatment and overall survival in comparison with PET/CT or established oncologic factors known to affect survival. Materials and Methods The institutional review board approved this prospective intraindividual comparative study in 36 consecutive patients (25 women) with liver-dominant metastases (20 colorectal, 14 breast, two other) (mean age, 60 years ± 10 [standard deviation]) who underwent fluorine 18 (¹⁸F) fluorodeoxyglucose (FDG) PET/CT and DW MRI before and 4-6 weeks after ⁹⁰Y radioembolization. DW MRI response was defined as a mean minimal apparent diffusion coefficient increase of more than 30%; PET/CT response was defined as a mean maximal standardized uptake value decrease of more than 30%. Kaplan-Meier curves, log-rank test, and multivariable Cox regression analyses were used to compare patient survival as a function of imaging and Response Evaluation Criteria in Solid Tumors (RECIST) response, pretreatment Eastern Cooperative Oncology Group (ECOG) performance status (PS) (0 vs 1), hepatic tumor load (<25% vs ≥25%), and presence versus absence of extrahepatic disease. Results Thirty-five of the 36 patients were observed until death (median survival, 36 weeks). Response was observed with PET/CT in 18 of 36 patients (50%). Median survival was 39 weeks in patients who responded to PET/CT versus 27 weeks in those who did not (P = .60). Response was observed with DW MRI in 24 of 36 patients (67%). Median survival was 53 weeks in DW MRI responders versus 20 weeks in nonresponders (P = .01). At multivariable analysis, DW MRI response was the only independent predictor of survival (P < .01). Response based on RECIST parameters, ECOG PS, hepatic tumor load, and presence of extrahepatic metastases did not correlate with survival. Conclusion In patients with hepatic metastases undergoing ⁹⁰Y radioembolization, prediction of response to therapy with DW MRI was superior to that with PET/CT and established oncologic factors.

90Y Resin Microspheres Radioembolization for Colon Cancer Liver Metastases Using Full-Strength Contrast Material

OBJECTIVES

To assess safety and efficacy of ⁹⁰Y resin microspheres administration using undiluted non-ionic contrast material (UDCM) {100% Omnipaque-300 (Iohexol)} in both the "B" and "D" lines.

MATERIALS AND METHODS

We reviewed all colorectal cancer liver metastases patients treated with ⁹⁰Y resin microspheres radioembolization (RAE) from 2009 to 2017. As of April 2013, two experienced operators started using UDCM (study group) instead of standard sandwich infusion (control group). Occurrence of myelosuppression (leukopenia, neutropenia, erythrocytopenia or/and thrombocytopenia), stasis, nontarget delivery (NTD), median fluoroscopy radiation dose (FRD), median infusion time (IT), liver progression-free (LPFS) and overall survivals (OS) was evaluated. Complications within 6 months post-RAE were reported according to CTCAE v3.0 criteria.

RESULTS

Study and control groups comprised 23(28%) and 58(72%) patients, respectively. Median follow-up was 9.1 months. There was no statistically significant difference in myelosuppression incidence within 6 months post-RAE between groups. Median FRD and IT for study and control groups were 44.6 vs. 97.35 Gy/cm² (p = 0.048) and 31 vs. 39 min (p = 0.006), respectively. A 38% lower stasis incidence in study group was not significant (p = 0.34). NTD occurred in 1/27(4%) study vs. 5/73(7%) control group procedures (p = 1). Grade 1-2 and grade 3-4 toxicities between study and control group patients were 36%(8/22) vs. 45%(26/58), p = 0.61 and 9%(2/22) vs. 16%(9/58), p = 0.72, respectively. There was no difference in LPFS and OS between groups.

CONCLUSION

Administration of ⁹⁰Y resin microspheres using UDCM in both lines is safe and effective, resulting in lower fluoroscopy radiation dose and shorter infusion time, without evidence of myelosuppression or increased stasis incidence.

Combined [18F]-Fluoroethylcholine PET/CT and 99mTc-Macroaggregated Albumin SPECT/CT Predict Survival in Patients With Intermediate-Stage Hepatocellular Carcinoma

AIM

The aim of this study was to retrospectively analyze the prognostic value of combined Tc-macroaggregated albumin (MAA) SPECT/CT and [F]-fluoroethylcholine (FEC) PET/CT before radioembolization for survival of patients with intermediate-stage hepatocellular carcinoma.

METHODS

Twenty-four patients with known hepatocellular carcinoma Barcelona Clinic Liver Cancer stage B were eligible for this analysis. All patients were scheduled for radioembolization and received a pretherapeutic [F]FEC PET/CT scan as well as Tc-MAA SPECT/CT for hepatopulmonary shunting. Laboratory and semiquantitative PET parameters and morphologic and metabolic (intersection) volumes of MAA and FEC were evaluated. Spearman correlation with overall survival, receiver operating curve analyses, univariate and multivariate Cox regression, and Kaplan-Meier-analysis was applied.

RESULTS

All patients (5 female/19 male) are deceased within the observational period. Median survival was 395 days (±51 days; range, 23-1122 days). The percentage of hypervascularized metabolically active tumor volume (vascularized tumor ratio; defined as high MAA and FEC uptake) correlated significantly with survival. Vascularized tumor ratio was a significant predictor in univariate and multivariate analyses (P = 0.026; hazard ratio, 11.65; 95% confidence interval, 1.62-83.73; P = 0.015). Statistical significance was not reached by all other variables in multivariate analysis. Receiver operating curve analysis for 1-year survival revealed an area under the curve of 0.77 (P = 0.024) for vascularized tumor ratio. At a cutoff value of 9%, sensitivity, specificity, and positive and negative prediction were 83%, 67%, and 71% and 80% (P = 0.036). Patients with a higher tumor vascularization had a median survival of 274 ± 80 versus 585 ± 284 days (P = 0.015).

CONCLUSIONS

Hepatocellular carcinoma with high vascularization in metabolic active areas as assessed by combined FEC PET/CT and Tc-MAA SPECT/CT represents an unfavorable subgroup with reduced overall survival after radioembolization.

Yttrium-90 resin microspheres and their use in the treatment of intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma (ICC) is a severe and rapidly progressive hepatic tumor. Surgery is often impracticable due to locally advanced presentation. On the other hand, chemotherapy has demonstrated only limited effectiveness. For these reasons, liver-directed therapies have been successfully applied for treating ICC. In particular, radioembolization with Yttrium-90 (90Y)-labeled spheres has been reported to be a promising therapeutic approach for this neoplasia. Two commercial forms of 90Y-labeled spheres are available: glass (TheraSphere®) and resin (SIR-Spheres®) microspheres. The aim of the present paper is to review the existing literature on the use of the resin microspheres for the treatment of unresectable and chemorefractory ICC, focusing on the methodology, clinical applications and side effects.

Current and Future Treatment of Hepatocellular Carcinoma: An Updated Comprehensive Review

Hepatocellular carcinoma (HCC) is among the leading causes of cancer-related mortality. The principal treatment is surgical resection or liver transplantation, depending on whether the patient is a suitable transplant candidate. However, in most patients with HCC the diagnosis is often late, thereby excluding the patients from definitive surgical resection. Medical treatment includes sorafenib, which is the most commonly used systemic therapy; although, it has been shown to only minimally impact patient survival by several months. Chemotherapy and radiotherapy are generally ineffective. Due to the poor prognosis of patients with HCC, newer treatments are needed with several being in development, either in pre-clinical or clinical studies. In this review article, we provide an update on the current and future medical and surgical management of HCC.

Phantom and clinical evaluation of the effect of full Monte Carlo collimator modelling in post-SIRT yttrium-90 Bremsstrahlung SPECT imaging

Background

Post-therapy SPECT/CT imaging of ⁹⁰Y microspheres delivered to hepatic malignancies is difficult, owing to the continuous, high-energy Bremsstrahlung spectrum emitted by ⁹⁰Y. This study aimed to evaluate the utility of a commercially available software package (HybridRecon, Hermes Medical Solutions AB) which incorporates full Monte Carlo collimator modelling. Analysis of image quality was performed on both phantom and clinical images in order to ultimately provide a recommendation of an optimum reconstruction for post-therapy ⁹⁰Y microsphere SPECT/CT imaging.

A 3D-printed anthropomorphic liver phantom was filled with ⁹⁰Y with a sphere-to-background ratio of 4:1 and imaged on a GE Discovery 670 SPECT/CT camera. Datasets were reconstructed using ordered-subsets expectation maximization (OSEM) 1–7 iterations in order to identify the optimal OSEM reconstruction (5 iterations, 15 subsets). Quantitative analysis was subsequently carried out on phantom datasets obtained using four reconstruction algorithms: the default OSEM protocol (2 iterations, 10 subsets) and the optimised OSEM protocol, both with and without full Monte Carlo collimator modelling. The quantitative metrics contrast recovery (CR) and background variability (BV) were calculated.

The four algorithms were then used to retrospectively reconstruct 10 selective internal radiation therapy (SIRT) patient datasets which were subsequently blind scored for image quality by a consultant radiologist.

Results

The optimised OSEM reconstruction (5 iterations, 15 subsets with full MC collimator modelling) increased the CR by 42% (p < 0.001) compared to the default OSEM protocol (2 iterations, 10 subsets). The use of full Monte Carlo collimator modelling was shown to further improve CR by 14% (30 mm sphere, CR = 90%, p < 0.05).

The consultant radiologist had a significant preference for the optimised OSEM over the default OSEM protocol (p < 0.001), with the optimised OSEM being the favoured reconstruction in every one of the 10 clinical cases presented.

Conclusions

OSEM (5 iterations, 15 subsets) with full Monte Carlo collimator modelling is quantitatively the optimal image reconstruction for post-SIRT ⁹⁰Y Bremsstrahlung SPECT/CT imaging. The use of full Monte Carlo collimator modelling for correction of image-degrading effects significantly increases contrast recovery without degrading clinical image quality.

[Selective intraarterial radiotherapy (SIRT) of malignant liver tumors]

Die Leitlinie soll medizinisches Fachpersonal und onkologisch tätige Ärzte bei der Auswahl geeigneter Patienten, der Planung, Vorbereitung und Durchführung einer SIRT zur Behandlung primärer und sekundärer maligner Lebertumoren unterstützen. Schwerpunkte sind personelle, technische und organisatorische Anforderungen an das Therapiezentrum einschließlich Strahlenschutz, d. h. insbesondere die Notwendigkeit einer interdisziplinären Patientenselektion in Tumorboards und die Anforderungen an das Team, das die Therapie durchführt und einen Medizinphysikexperten einbeziehen muss. Die Zielsetzung der Therapie, die erforderlichen Daten und Voruntersuchungen für die Indikationsstellung und Therapieplanung und ihre Implikationen für die Vermeidung von Komplikationen werden dargestellt, ebenso Anforderungen an die Aufklärung des Patienten. Die Nachsorge wird beschrieben und auf die Notwendigkeit einer interdisziplinären Zusammenarbeit auch mit heimatnahen behandelnden Ärzten hingewiesen.

Stereotactic body radiotherapy used as a bridge to liver transplant in patients with hepatocellular carcinoma and Child-Pugh score ≥8 cirrhosis

INTRODUCTION

To report on SBRT as a bridge to OLT for patients with HCC and Child-Pugh ≥8 cirrhosis.

METHODS

Retrospective review of 15 patients, treated from 2010-2017. Three patients excluded secondary to delisting from prohibitive substance. Twelve patients (17 lesions) included for final analysis. Hepatic SPECT functional treatment planning utilized.

RESULTS

The median age of 60 years with a median CP 9 and MELD 14. The median SBRT dose was 40 Gy in 5 fractions, and median tumor size was 2.3cm (1.2-5.3cm). Median follow-up and survival was 40-months and 46-months, respectively. One patient succumbed to renal/hepatic failure before OLT. Radiographic response was 80%. pCR at explant was 46%. No grade ≥ 3 acute toxicities. Median time to progression of CP ≥ 2 was 9.7-months and MELD progression was not met before OLT.

CONCLUSION

SBRT with functional treatment planning can be used safely as a bridge to OLT in select patients with CP ≥8 cirrhosis.

The effect of selective internal radiation therapy with yttrium-90 resin microspheres on lung carbon monoxide diffusion capacity

Background

Selective internal radiation therapy (SIRT) with embolization of branches of the hepatic artery is a valuable therapeutic tool for patients with hepatic malignancies; however, it is also associated with lung injury risk due to shunting. Diffusion capacity of the lungs for carbon monoxide (DLCO) is a clinically significant lung function test, and worsening in DLCO is suggested to reflect a limited gas exchange reserve caused by the potential toxicity of chemoradiotherapy or it may be a marker of related lung injury. This study aimed to examine the changes in DLCO during SIRT with resin microspheres in newly treated and retreated patients. Forty consecutive patients who received SIRT for a variety of malignant conditions were included. All subjects were treated with Yttrium-90 labelled resin microspheres. DLCO tests were performed after the procedures. In addition, patients were specifically followed for radiation pneumonitis.

Results

The mean DLCO did not significantly change after the first (82.8 ± 19.4 vs. 83.1 ± 20.9, p = 0.921) and the second treatments (87.4 ± 19.7 vs. 88.6 ± 23.2, p = 0.256). Proportion of patients with impaired DLCO at baseline was not altered significantly after the first (37.5 vs. 45.0%, p = 0.581) and the second treatments (27.3 vs. 27.3%, p = 1.000). Also, percent change in DLCO values did not correlate with radiation dose, lung shunt fraction, or lung exposure dose (p > 0.05 for all comparisons). None of the patients developed radiation pneumonitis.

Conclusions

Our results suggest that no significant change in DLCO in association with SIRT occurs, both after the first or the second treatment sessions. Further larger studies possibly with different protocols are warranted to better delineate DLCO changes after SIRT in a larger spectrum of patients.

Aspects of images in magnetic resonance of liver tumors treated with transarterial selective internal radiotherapy with yttrium-90

Transarterial selective internal radiation therapy with yttrium-90, also known as radioembolization, is a therapy based on the administration of resin or glass microspheres loaded with the radioisotope yttrium-90, via selective arterial catheterization of tumor-feeding vessels. It is classified as a type of locoregional therapy and its main goal is to treat patients with primary or secondary hepatic lesions that are unresectable and not responsive to other therapies. Since it is a new technology still restricted to very few hospitals in Brazil, but used in patients throughout the country, it is necessary to demonstrate the main aspects of hepatic lesions treated with selective internal radiation therapy found in magnetic resonance imaging, and to make specific considerations on interpretation of these images. The objective of this report is to demonstrate the main aspects of magnetic resonance imaging of unresectable primary or secondary hepatic lesions, in patients submitted to transarterial selective internal radiation therapy.

The role of angled-tip microcatheter and microsphere injection velocity in liver radioembolization: A computational particle-hemodynamics study

Liver radioembolization is a promising treatment option for combating liver tumors. It is performed by placing a microcatheter in the hepatic artery and administering radiation-emitting microspheres through the arterial bloodstream so that they get lodged in the tumoral bed. In avoiding nontarget radiation, the standard practice is to conduct a pretreatment, in which the microcatheter location and injection velocity are decided. However, between pretreatment and actual treatment, some of the parameters that influence the particle distribution in the liver can vary, resulting in radiation-induced complications. The present study aims to analyze the influence of a commercially available microcatheter with an angled tip and particle injection velocity in terms of segment-to-segment particle distribution. Specifically, 4 tip orientations and 2 injection velocities are combined to yield a set of 8 numerical simulations of the particle-hemodynamics in a patient-specific truncated hepatic artery. For each simulation, 4 cardiac pulses are simulated. Particles are injected during the first cycle, and the remaining pulses enable the majority of the injected particles to exit the computational domain. Results indicate that, in terms of injection velocity, particles are more spread out in the cross-sectional lumen areas as the injection velocity increases. The tip's orientation also plays a role because it influences the near-tip hemodynamics, therefore altering the particle travel through the hepatic artery. However, results suggest that particle distribution tries to match the blood flow split, therefore particle injection velocity and microcatheter tip orientation playing a minor role in segment-to-segment particle distribution.

Recommendations for radioembolisation after liver surgery using yttrium-90 resin microspheres based on a survey of an international expert panel

INTRODUCTION

Guidelines on how to adjust activity in patients with a history of liver surgery who are undergoing yttrium-90 radioembolisation (90Y-RE) are lacking. The aim was to study the variability in activity prescription in these patients, between centres with extensive experience using resin microspheres 90Y-RE, and to draw recommendations on activity prescription based on an expert consensus.

METHODS

The variability in activity prescription between centres was investigated by a survey of international experts in the field of 90Y-RE. Six representative post-surgical patients (i.e. comparable activity prescription, different outcome) were selected. Information on patients' disease characteristics and data needed for activity calculation was presented to the expert panel. Reported was the used method for activity prescription and whether, how and why activity reduction was found indicated.

RESULTS

Ten experts took part in the survey. Recommendations on activity reduction were highly variable between the expert panel. The median intra-patient range was 44 Gy (range 18-55 Gy). Reductions in prescribed activity were recommended in 68% of the cases. In consensus, a maximum DTarget of 50 Gy was recommended.

CONCLUSION

With a current lack of guidelines, large variability in activity prescription in post-surgical patients undergoing 90Y-RE exists. In consensus, DTarget ≤50 Gy is recommended.

KEY POINTS

• BSA method does not account for a decreased remnant liver volume after surgery. • In post-surgical patients, a volume-based activity determination method is recommended. • In post-surgical patients, a mean D Target of ≤ 50Gy should be aimed for.

Pretreatment albumin may aid in patient selection for intrahepatic Y-90 microsphere transarterial radioembolization (TARE) for malignancies of the liver

Background

Hepatic malignancies are common including primary malignancies and metastases. Transarterial radioembolization (TARE) is an important treatment option. We reviewed safety and efficacy of (TARE) in our patients to identify factors that may impact treatment outcomes in a heterogeneous population.

Methods

All patients that received TARE at the Medical University of South Carolina from March 2006 through May of 2014 were included. Kaplan-Meier estimates on overall survival (OS) from date of first procedure are reported. Potential prognostic factors for OS were evaluated using log rank tests and Cox proportional hazards models.

Results

In the 114 patients that received TARE at our institution, median follow-up was 6.4 months (range, 0-86 months) with the following histologies: colorectal (CR) n=55, hepatocellular (HC) n=20, cholangiocarcinoma (CC) n=16, neuroendocrine (NE) n=12, breast (BR) n=6, other n=5. At least 1 line of prior systemic therapy was noted in 79% of patients. Median OS was significantly better with NE and BR histology, and in those with normal albumin levels. With an albumin >3.4 median OS was 10.3 months, but was only 3.1 months with an albumin <3 g/dL. Grade ≥2 toxicity was observed in 22 patients (19.3%) including 9 (7.9%) with Grade 3 and 1 (0.9%) with Grade 4 toxicity.

Conclusions

TARE is a relatively safe and effective treatment for intrahepatic malignancies. Patients with NE and BR histology as well as those with better hepatic synthetic function were associated with significantly better survival. Our data suggest that patients with albumin below 3 g/dL may not derive significant benefit from TARE.

Hepatocellular carcinoma treatment: ablation and arterial embolization

Percutaneous and endovascular techniques take an important role in the therapeutic management of patients with hepatocarcinoma. Different techniques of percutaneous ablation, especially indicated in tumors up to 2cm diameter offer, at least, similar results to surgical resection. Taking advantage of double hepatic vascularization and exclusive tumor nutrition by the artery, several endovascular techniques of treating the tumor have been developed. Intra-arterial administration of embolizing particles, alone or charged with drug (chemoembolization), will produce ischemia and consequent necrosis with excellent results in selected patients. Certain types of particles may exclusively be carriers of a therapeutic agent when they incorporate a radioisotope that facilitates the direct intratumoral selective irradiation (radioembolization). This technique has demonstrated its efficacy in lesions not susceptible to be treated with other methods and should be considered, together with ablation and chemoembolization, in the therapeutic algorithms of hepatocarcinoma.

Treatment options for unresectable HCC with a focus on SIRT with Yttrium-90 resin microspheres

Hepatocellular carcinoma (HCC), the predominant form of primary liver cancer, is the second leading cause of cancer-related deaths across the globe. Only a small percentage of HCC patients (~20%-30%) are diagnosed at an early stage when first-line treatment options may be effective. The majority of HCC patients (>70%) are diagnosed with unresectable disease and given a poor overall prognosis. Current treatment guidelines recommend locoregional therapy with transarterial chemoembolisation (TACE) and systemic therapy with sorafenib as first-line treatment for patients with intermediate and advanced stage HCC. However, multiple factors including contraindications, technical considerations and treatment-related toxicities pose significant challenges in achieving favourable treatment outcomes, underscoring the need for a paradigm shift in managing these patients. In 2002, yttrium-90 (Y-90) resin microspheres was approved by the U.S. Food and Drug Administration (FDA) for the treatment of unresectable metastatic colorectal cancer to the liver with adjuvant floxuridine chemotherapy. However, thousands of patients with unresectable HCC have also been treated with resin Y-90. For over two decades, several small-scale prospective trials and retrospective studies have investigated and reported on the efficacy of locoregional selective internal radiation therapy (SIRT) with Y-90 microspheres in treating unresectable HCC. Although it is currently a treatment option for intermediate-stage HCC patients, mainstream clinical application of resin Y-90 has been largely limited because of the lack of sufficient clinical data from a randomised controlled trial. This could change with the imminent announcement of results from the phase 3 Sorafenib vs Radioembolization in Advanced Hepatocellular carcinoma (SARAH) trial. To provide the foundation and context for interpreting results from the SARAH trial, this article provides an overview of treatment modalities and current challenges in managing unresectable HCC. There is also a review of key prospective and retrospective studies evaluating the use of Y-90 SIRT, specifically Y-90 resin microspheres in unresectable HCC, which led to the development of the SARAH trial.

METHODS

To identify relevant publications, the PubMed database was queried using one or more of the following search terms alone or in combination with Boolean operators: epidemiology, hepatocellular, hepatocellular cancer, hepatocellular carcinoma, unresectable, radioembolisation, selective internal radiation therapy, SIR-Spheres, yttrium 90, TACE, and sorafenib. The results were sorted or filtered by "Author", "Publication dates" or "Article types" to identify articles relevant to each section of the review. To ensure that information on ongoing clinical trials involving Y-90 resin was included, we conducted a search on "ClinicalTrials.gov", by combining the search terms "HCC" OR "hepatocellular carcinoma" with "Y 90" OR "yttrium 90" OR "radioembo", and screened for studies that involved treatment with Y-90 resin microspheres.

Estimation of lung shunt fraction from simultaneous fluoroscopic and nuclear images

Radioembolisation with yttrium-90 (⁹⁰Y) is increasingly used as a treatment of unresectable liver malignancies. For safety, a scout dose of technetium-99m macroaggregated albumin (^99mTc-MAA) is used prior to the delivery of the therapeutic activity to mimic the deposition of ⁹⁰Y. One-day procedures are currently limited by the lack of nuclear images in the intervention room. To cope with this limitation, an interventional simultaneous fluoroscopic and nuclear imaging device is currently being developed. The purpose of this simulation study was to evaluate the accuracy of estimating the lung shunt fraction (LSF) of the scout dose in the intervention room with this device and compare it against current clinical methods.

METHODS

A male and female XCAT phantom, both with two respiratory profiles, were used to simulate various LSFs resulting from a scout dose of 150 MBq ^99mTc-MAA. Hybrid images were Monte Carlo simulated for breath-hold (5 s) and dynamic breathing (10 frames of 0.5 s) acquisitions. Nuclear images were corrected for attenuation with the fluoroscopic image and for organ overlap effects using a pre-treatment CT-scan. For comparison purposes, planar scintigraphy and mobile gamma camera images (both 300 s acquisition time) were simulated. Estimated LSFs were evaluated for all methods and compared to the phantom ground truth.

RESULTS

In the clinically relevant range of 10-20% LSF, hybrid imaging overestimated LSF with approximately 2 percentage points (pp) and 3 pp for the normal and irregular breathing phantoms, respectively. After organ overlap correction, LSF was estimated with a more constant error. Errors in planar scintigraphy and mobile gamma camera imaging were more dependent on LSF, body shape and breathing profile.

CONCLUSION

LSF can be estimated with a constant minor error with a hybrid imaging device. Estimated LSF is highly dependent on true LSF, body shape and breathing pattern when estimated with current clinical methods. The hybrid imaging device is capable of accurately estimating LSF within a few seconds in an interventional setting.

Liver Metastases in Pancreatic Acinar Cell Carcinoma Treated with Selective Internal Radiation Therapy with Y-90 Resin Microspheres

Background

Pancreatic acinar cell carcinoma (PACC) is a rare tumor. Surgical resection is the treatment of choice when feasible, but there are no clear recommendations for patients with advanced disease. Liver-directed therapy with Y-90 selective internal radiation therapy (SIRT) has been used to treat hepatic metastases from pancreatic tumors. We describe a case of PACC liver metastases treated with SIRT.

Case Report

59-year-old man was admitted with an infiltrative, solid lesion in pancreatic tail diagnosed as PACC. Lymph nodes in the hepatic hilum were enlarged, and many metastatic liver nodules were observed. After partial pancreatectomy, the left and right lobes of the liver were separately treated with Y-90 resin microspheres. Follow-up imaging revealed that all hepatic nodules shrank by at least 50%, and 3 nodules disappeared completely. Lipase concentration was 8407 U/L at baseline, rose to 12,705 U/L after pancreatectomy, and declined to 344 U/L after SIRT. Multiple rounds of chemotherapy in the subsequent year shrank the hepatic tumors further; disease then progressed, but a third line of chemotherapy shrank the tumors again, 16 months after SIRT treatment.

Conclusion

SIRT had a positive effect on liver metastases from PACC. In conjunction with systemic therapy, SIRT can achieve sustained disease control.

Radioembolisation of hepatocellular carcinoma: a primer

Transarterial radioembolisation (TARE) has gained increasing acceptance as an additional/alternative locoregional treatment option for hepatocellular carcinoma, and colorectal hepatic metastases that present beyond potentially curative options. This is a catheter-based transarterial selective internal brachytherapy that involves injection of radioactive microspheres (usually Y-90) that are delivered selectively to the liver tumours. Owing to the combined radioactive and microembolic effect, the findings at follow-up imaging are significantly different from that seen with other transarterial treatment options. Considering increasing confidence among clinicians, refinement in techniques and increasing number of ongoing trials, TARE is expected to gain further acceptance and become an important tool in the armamentarium for the treatment of liver malignancies. So it is imperative that all radiologists involved in the management of liver malignancies are well versed with TARE to facilitate appropriate discussion at multidisciplinary meetings to direct further management. In this article, we provide a comprehensive review on various aspects of radioembolisation with Y-90 for hepatocellular carcinoma including the patient selection, treatment planning, radiation dosimetry and treatment, side effects, follow-up imaging and future direction.