Radioembolization of hepatic tumors

Advanced targeted microsphere embolization for arteriovenous malformations: state-of-the-art and future directions

BACKGROUND

Arteriovenous malformations (AVMs) present a significant therapeutic challenge, as current treatment modalities frequently fail to achieve complete and rapid obliteration and are associated with substantial morbidity in both the short and long term. This underscores the critical need for innovative therapeutic strategies that enable efficient AVM obliteration while minimizing patient risk. The current review aims to comprehensively assess the role of ATME in AVM management, examining its clinical efficacy, associated risks and benefits, and the economic and ethical implications to provide valuable foundation for future studies and guiding development in treatment strategies for AVMs.

RESULTS

Advanced targeted microsphere embolization (ATME) has emerged as a promising therapeutic option, initially developed for the localized treatment of AVMs and unresectable tumors, including liver cancer. By providing targeted delivery, ATME offers potential advantages over conventional approaches in achieving effective local control.

CONCLUSIONS

ATME are safe and effective for vascular disease and cancer. Although evidence for microspheres in AVMs is scarce, results are promising. Future research could refine eligibility criteria, evaluate treatment techniques, and optimize ATME.

Functional hydrogels for hepatocellular carcinoma: therapy, imaging, and in vitro model

Hepatocellular carcinoma (HCC) is among the most common malignancies worldwide and is characterized by high rates of morbidity and mortality, posing a serious threat to human health. Interventional embolization therapy is the main treatment against middle- and late-stage liver cancer, but its efficacy is limited by the performance of embolism, hence the new embolic materials have provided hope to the inoperable patients. Especially, hydrogel materials with high embolization strength, appropriate viscosity, reliable security and multifunctionality are widely used as embolic materials, and can improve the efficacy of interventional therapy. In this review, we have described the status of research on hydrogels and challenges in the field of HCC therapy. First, various preparation methods of hydrogels through different cross-linking methods are introduced, then the functions of hydrogels related to HCC are summarized, including different HCC therapies, various imaging techniques, in vitro 3D models, and the shortcomings and prospects of the proposed applications are discussed in relation to HCC. We hope that this review is informative for readers interested in multifunctional hydrogels and will help researchers develop more novel embolic materials for interventional therapy of HCC.

Physics-Guided Deep Scatter Estimation by Weak Supervision for Quantitative SPECT

Accurate scatter estimation is important in quantitative SPECT for improving image contrast and accuracy. With a large number of photon histories, Monte-Carlo (MC) simulation can yield accurate scatter estimation, but is computationally expensive. Recent deep learning-based approaches can yield accurate scatter estimates quickly, yet full MC simulation is still required to generate scatter estimates as ground truth labels for all training data. Here we propose a physics-guided weakly supervised training framework for fast and accurate scatter estimation in quantitative SPECT by using a 100× shorter MC simulation as weak labels and enhancing them with deep neural networks. Our weakly supervised approach also allows quick fine-tuning of the trained network to any new test data for further improved performance with an additional short MC simulation (weak label) for patient-specific scatter modelling. Our method was trained with 18 XCAT phantoms with diverse anatomies / activities and then was evaluated on 6 XCAT phantoms, 4 realistic virtual patient phantoms, 1 torso phantom and 3 clinical scans from 2 patients for 177Lu SPECT with single / dual photopeaks (113, 208 keV). Our proposed weakly supervised method yielded comparable performance to the supervised counterpart in phantom experiments, but with significantly reduced computation in labeling. Our proposed method with patient-specific fine-tuning achieved more accurate scatter estimates than the supervised method in clinical scans. Our method with physics-guided weak supervision enables accurate deep scatter estimation in quantitative SPECT, while requiring much lower computation in labeling, enabling patient-specific fine-tuning capability in testing.

Optimization of the Clinical Effectiveness of Radioembolization in Hepatocellular Carcinoma with Dosimetry and Patient-Selection Criteria

Selective internal radiation therapy (SIRT) is part of the treatment strategy for hepatocellular carcinoma (HCC). Strong clinical data demonstrated the effectiveness of this therapy in HCC with a significant improvement in patient outcomes. Recent studies demonstrated a strong correlation between the tumor response and the patient outcome when the tumor-absorbed dose was assessed by nuclear medicine imaging. Dosimetry plays a key role in predicting the clinical response and can be optimized using a personalized method of activity planning (multi-compartmental dosimetry). This paper reviews the main clinical results of SIRT in HCC and emphasizes the central role of dosimetry for improving it effectiveness. Moreover, some patient and tumor characteristics predict a worse outcome, and toxicity related to SIRT treatment of advanced HCC patient selection based on the performance status, liver function, tumor characteristics, and tumor targeting using technetium-99m macro-aggregated albumin scintigraphy can significantly improve the clinical performance of SIRT.

Microspheres Used in Liver Radioembolization: From Conception to Clinical Effects

Inert microspheres, labeled with several radionuclides, have been developed during the last two decades for the intra-arterial treatment of liver tumors, generally called Selective Intrahepatic radiotherapy (SIRT). The aim is to embolize microspheres into the hepatic capillaries, accessible through the hepatic artery, to deliver high levels of local radiation to primary (such as hepatocarcinoma, HCC) or secondary (metastases from several primary cancers, e.g., colorectal, melanoma, neuro-endocrine tumors) liver tumors. Several types of microspheres were designed as medical devices, using different vehicles (glass, resin, poly-lactic acid) and labeled with different radionuclides, 90Y and 166Ho. The relationship between the microspheres' properties and the internal dosimetry parameters have been well studied over the last decade. This includes data derived from the clinics, but also computational data with various millimetric dosimetry and radiobiology models. The main purpose of this paper is to define the characteristics of these radiolabeled microspheres and explain their association with the microsphere distribution in the tissues and with the clinical efficacy and toxicity. This review focuses on avenues to follow in the future to optimize such particle therapy and benefit to patients.

Efficient Monte-Carlo based system modelling for image reconstruction in preclinical pinhole SPECT

The use of multi-pinhole collimation has enabled ultra-high-resolution imaging of SPECT and PET tracers in small animals. Key for obtaining high-quality images is the use of statistical iterative image reconstruction with accurate energy-dependent photon transport modelling through collimator and detector. This can be incorporated in a system matrix that contains the probabilities that a photon emitted from a certain voxel is detected at a specific detector pixel. Here we introduce a fast Monte-Carlo based (FMC-based) matrix generation method for pinhole imaging that is easy to apply to various radionuclides. The method is based on accelerated point source simulations combined with model-based interpolation to straightforwardly change or combine photon energies of the radionuclide of interest. The proposed method was evaluated for a VECTor PET-SPECT system with (i) a HE-UHR-M collimator and (ii) an EXIRAD-3D 3D autoradiography collimator. Both experimental scans with^99mTc,¹¹¹In, and¹²³I, and simulated scans with⁶⁷Ga and⁹⁰Y were performed for evaluation. FMC was compared with two currently used approaches, one based on a set of point source measurements with^99mTc (dubbed traditional method), and the other based on an energy-dependent ray-tracing simulation (ray-tracing method). The reconstruction results show better image quality when using FMC-based matrices than when applying the traditional or ray-tracing matrices in various cases. FMC-based matrices generalise better than the traditional matrices when imaging radionuclides with energies deviating too much from the energy used in the calibration and are computationally more efficient for very-high-resolution imaging than the ray-tracing matrices. In addition, FMC has the advantage of easily combining energies in a single matrix which is relevant when imaging radionuclides with multiple photopeak energies (e.g.⁶⁷Ga and¹¹¹In) or with a continuous energy spectrum (e.g.⁹⁰Y). To conclude, FMC is an efficient, accurate, and versatile tool for creating system matrices for ultra-high-resolution pinhole SPECT.

Tumor response prediction in 90Y radioembolization with PET-based radiomics features and absorbed dose metrics

Purpose

To evaluate whether lesion radiomics features and absorbed dose metrics extracted from post-therapy ⁹⁰Y PET can be integrated to better predict outcomes in microsphere radioembolization of liver malignancies

Methods

Given the noisy nature of ⁹⁰Y PET, first, a liver phantom study with repeated acquisitions and varying reconstruction parameters was used to identify a subset of robust radiomics features for the patient analysis. In 36 radioembolization procedures, ⁹⁰Y PET/CT was performed within a couple of hours to extract 46 radiomics features and estimate absorbed dose in 105 primary and metastatic liver lesions. Robust radiomics modeling was based on bootstrapped multivariate logistic regression with shrinkage regularization (LASSO) and Cox regression with LASSO. Nested cross-validation and bootstrap resampling were used for optimal parameter/feature selection and for guarding against overfitting risks. Spearman rank correlation was used to analyze feature associations. Area under the receiver-operating characteristics curve (AUC) was used for lesion response (at first follow-up) analysis while Kaplan-Meier plots and c-index were used to assess progression model performance. Models with absorbed dose only, radiomics only, and combined models were developed to predict lesion outcome.

Results

The phantom study identified 15/46 reproducible and robust radiomics features that were subsequently used in the patient models. A lesion response model with zone percentage (ZP) and mean absorbed dose achieved an AUC of 0.729 (95% CI 0.702–0.758), and a progression model with zone size nonuniformity (ZSN) and absorbed dose achieved a c-index of 0.803 (95% CI 0.790–0.815) on nested cross-validation (CV). Although the combined models outperformed the radiomics only and absorbed dose only models, statistical significance was not achieved with the current limited data set to establish expected superiority.

Conclusion

We have developed new lesion-level response and progression models using textural radiomics features, derived from ⁹⁰Y PET combined with mean absorbed dose for predicting outcome in radioembolization. These encouraging, but limited results, will need further validation in independent and larger datasets prior to any clinical adoption.

Supplementary Information

Supplementary information accompanies this paper at 10.1186/s40658-020-00340-9.

Liver Resection After Selective Internal Radiation Therapy with Yttrium-90: Safety and Outcomes

Introduction

Selective internal radiotherapy (SIRT) with yttrium-90 (Y-90) is an intra-arterial therapy for hepatic malignancy in patients who are unsuitable for surgical resection. This treatment is considered palliative, although some patients can demonstrate a response that is adequate to facilitate surgical resection with curative intent.

Methods

All patients who underwent liver resection post SIRT were reviewed. Data gathered included patient demographics, tumor type, surgical details, and post-operative outcomes.

Results

Twelve patients underwent SIRT followed by liver resection (7 males and 5 females). Pathologies were hepatocellular carcinoma (n = 5), metastatic colorectal cancer (n = 5), and neuroendocrine tumor (n = 2). Lesional response (size, volume, and RECIST (response evaluation criteria in solid tumors)) was calculated and where appropriate functional liver remnant (FLR) is presented. Mean FLR increase was 264cm³ (range − 123 to 909), and all cases demonstrated a partial response according to RECIST with a mean largest lesion volume reduction of 475cm³ (range 14–1632). No post-SIRT complications were noted. Hepatectomy occurred at a mean of 322 days from SIRT treatment. Ninety-day morbidity was 67% (n = 6), complications post-surgery were analyzed according to the Clavien-Dindo classification scale; a total of 15 events occurred in 6 patients. Ninety-day mortality of 11% (n = 1).

Conclusion

In selected cases, liver resection is possible post SIRT. As this can represent a potentially curative option, it is important to reconsider resection in the follow-up of patients undergoing SIRT. Post-operative complications are noted following major and extended liver resection. Therefore, further studies are needed to improve patient selection.

Algorithms and Analyses for Joint Spectral Image Reconstruction in Y-90 Bremsstrahlung SPECT

Quantitative yttrium-90 (Y-90) SPECT imaging is challenging due to the nature of Y-90, an almost pure beta emitter that is associated with a continuous spectrum of bremsstrahlung photons that have a relatively low yield. This paper proposes joint spectral reconstruction (JSR), a novel bremsstrahlung SPECT reconstruction method that uses multiple narrow acquisition windows with accurate multi-band forward modeling to cover a wide range of the energy spectrum. Theoretical analyses using Fisher information and Monte-Carlo (MC) simulation with a digital phantom show that the proposed JSR model with multiple acquisition windows has better performance in terms of covariance (precision) than previous methods using multi-band forward modeling with a single acquisition window, or using a single-band forward modeling with a single acquisition window. We also propose an energy-window subset (ES) algorithm for JSR to achieve fast empirical convergence and maximum-likelihood based initialization for all reconstruction methods to improve quantification accuracy in early iterations. For both MC simulation with a digital phantom and experimental study with a physical multi-sphere phantom, our proposed JSR-ES, a fast algorithm for JSR with ES, yielded higher recovery coefficients (RCs) on hot spheres over all iterations and sphere sizes than all the other evaluated methods, due to fast empirical convergence. In experimental study, for the smallest hot sphere (diameter 1.6cm), at the 20th iteration the increase in RCs with JSR-ES was 66 and 31% compared with single wide and narrow band forward models, respectively. JSR-ES also yielded lower residual count error (RCE) on a cold sphere over all iterations than other methods for MC simulation with known scatter, but led to greater RCE compared with single narrow band forward model at higher iterations for experimental study when using estimated scatter.

Neutron-activated biodegradable samarium-153 acetylacetonate-poly-L-lactic acid microspheres for intraarterial radioembolization of hepatic tumors

BACKGROUND

Liver cancer is the 6^th most common cancer in the world and the 4^th most common death from cancer worldwide. Hepatic radioembolization is a minimally invasive treatment involving intraarterial administration of radioembolic microspheres.

AIM

To develop a neutron-activated, biodegradable and theranostics samarium-153 acetylacetonate (¹⁵³SmAcAc)-poly-L-lactic acid (PLLA) microsphere for intraarterial radioembolization of hepatic tumors.

METHODS

Microspheres with different concentrations of ¹⁵²SmAcAc (i.e., 100%, 150%, 175% and 200% w/w) were prepared by solvent evaporation method. The microspheres were then activated using a nuclear reactor in a neutron flux of 2 × 10¹² n/cm²/s¹, converting ¹⁵²Sm to Samarium-153 (¹⁵³Sm) via ¹⁵²Sm (n, γ) ¹⁵³Sm reaction. The SmAcAc-PLLA microspheres before and after neutron activation were characterized using scanning electron microscope, energy dispersive X-ray spectroscopy, particle size analysis, Fourier transform infrared spectroscopy, thermo-gravimetric analysis and gamma spectroscopy. The in-vitro radiolabeling efficiency was also tested in both 0.9% sodium chloride solution and human blood plasma over a duration of 550 h.

RESULTS

The SmAcAc-PLLA microspheres with different SmAcAc contents remained spherical before and after neutron activation. The mean diameter of the microspheres was about 35 µm. Specific activity achieved for ¹⁵³SmAcAc-PLLA microspheres with 100%, 150%, 175% and 200% (w/w) SmAcAc after 3 h neutron activation were 1.7 ± 0.05, 2.5 ± 0.05, 2.7 ± 0.07, and 2.8 ± 0.09 GBq/g, respectively. The activity of per microspheres were determined as 48.36 ± 1.33, 74.10 ± 1.65, 97.87 ± 2.48, and 109.83 ± 3.71 Bq for ¹⁵³SmAcAc-PLLA microspheres with 100%, 150%, 175% and 200% (w/w) SmAcAc. The energy dispersive X-ray and gamma spectrometry showed that no elemental and radioactive impurities present in the microspheres after neutron activation. Retention efficiency of ¹⁵³Sm in the SmAcAc-PLLA microspheres was excellent (approximately 99%) in both 0.9% sodium chloride solution and human blood plasma over a duration of 550 h.

CONCLUSION

The ¹⁵³SmAcAc-PLLA microsphere is potentially useful for hepatic radioembolization due to their biodegradability, favorable physicochemical characteristics and excellent radiolabeling efficiency. The synthesis of the formulation does not involve ionizing radiation and hence reducing the complication and cost of production.

Management of oligometastatic non-small cell lung cancer patients: Current controversies and future directions

Oligometastatic non-small cell lung cancer (NSCLC) describes an intermediate stage of NSCLC between localized and widely-disseminated disease. This stage of NSCLC is characterized by a limited number of metastases and a more indolent tumor biology. Currently, the management of oligometastatic NSCLC involves radical treatment (radiotherapy or surgery) that targets the metastatic lesions and the primary tumor to achieve disease control. This approach offers the potential to achieve prolonged survival in patients who, in the past, would have only received palliative measures. The optimal therapeutic strategies for the different scenarios of oligometastatic disease (intracranial vs extracranial disease, synchronous vs metachronous) remain undefined. Given the lack of head-to-head studies comparing radiotherapy to surgery in these patients, the decision to apply surgery or radiotherapy (with or without systemic treatment) must be based on prognostic factors that allow us to classify patients. This classification will allow us to select the most appropriate therapeutic strategy on an individualized basis. In the future, the molecular or microRNA profiles will likely improve the treatment selection process. The objective of the present article is to review the most relevant scientific evidence on the management of patients with oligometastatic NSCLC, focusing on the role of radiotherapy and surgery. We also discuss areas of controversy and future directions.

Assessing Spatial Concordance Between Theranostic Pairs Using Phantom and Patient-Specific Acceptance Criteria: Application to 99mTc-MAA SPECT/90Y-Microsphere PET

PURPOSE

Predictive 3-dimensional dosimetry requires spatial concordance between diagnostic and therapeutic activity distributions. We assess similarity between theranostic pairs (^99mTc-macroaggregated albumin [MAA] single photon emission computed tomography [SPECT] and ⁹⁰Y microsphere positron emission tomography [PET]) in patients using criteria that account for spatial resolution differences and misregistration.

METHODS AND MATERIALS

Phantom-based acceptance criteria were determined using a liver phantom filled with ^99mTc and ⁹⁰YCl₃ and scanned with SPECT/computed tomography [CT] and PET/CT, respectively. Gaussian blurring was applied to PET to match ^99mTc phantom scan image quality. After rigid registration between SPECT/CT and PET/CT, perturbations up to ±3 voxels were applied to determine the similarity metric (SM) sensitivity. ^99mTc-MAA SPECT/CT and ⁹⁰Y microsphere PET/CT image pairs/patients (n = 23) were processed analogously. SMs calculated included the Pearson correlation coefficient (ρ_r), Lin's concordance correlation coefficient (ρ_c), Spearman's rank correlation coefficient (ρ_s), the mean squared difference, and the Dice similarity coefficient (DSC). Patient-specific acceptance criteria were determined by evaluating the SMs of the blurred PET compared with itself misregistered.

RESULTS

After transforming PET to SPECT resolution, high similarity was found in phantom, with ρ_c, ρ_r, ρ_s > 0.98 ± 0.01, a mean squared difference of (4.1 ± 0.3) × 10^-4 and DSC > 0.85 ± 0.01 for investigated thresholds (5%, 30%, and 50%). SMs for patients varied from poor to good. A small percentage (13%-30%) of patient scans were acceptable using phantom-based acceptance criteria. The percentage increased slightly (17%-35%) using patient-specific acceptance criteria. DSC for most patients were substantially lower (average 0.95 vs 0.61 for 5% threshold) than phantom values.

CONCLUSIONS

At best, 35% of patients had an SM within the acceptance criteria established to account for imaging-related effects impacting spatial concordance between ^99mTc-MAA SPECT and ⁹⁰Y PET. Additional clinical factors should be evaluated in the future. The procedure of accounting for image-related effects when assessing spatial concordance can be applied to other theranostic pairs.

Impact of 90Y PET gradient-based tumor segmentation on voxel-level dosimetry in liver radioembolization

BACKGROUND

The purpose was to validate ⁹⁰Y PET gradient-based tumor segmentation in phantoms and to evaluate the impact of the segmentation method on reported tumor absorbed dose (AD) and biological effective dose (BED) in ⁹⁰Y microsphere radioembolization (RE) patients. A semi-automated gradient-based method was applied to phantoms and patient tumors on the ⁹⁰Y PET with the initial bounding volume for gradient detection determined from a registered diagnostic CT or MR; this PET-based segmentation (PS) was compared with radiologist-defined morphologic segmentation (MS) on CT or MRI. AD and BED volume histogram metrics (D90, D70, mean) were calculated using both segmentations and concordance/correlations were investigated. Spatial concordance was assessed using Dice similarity coefficient (DSC) and mean distance to agreement (MDA). PS was repeated to assess intra-observer variability.

RESULTS

In phantoms, PS demonstrated high accuracy in lesion volumes (within 15%), AD metrics (within 11%), high spatial concordance relative to morphologic segmentation (DSC > 0.86 and MDA < 1.5 mm), and low intra-observer variability (DSC > 0.99, MDA < 0.2 mm, AD/BED metrics within 2%). For patients (58 lesions), spatial concordance between PS and MS was degraded compared to in-phantom (average DSC = 0.54, average MDA = 4.8 mm); the average mean tumor AD was 226 ± 153 and 197 ± 138 Gy, respectively for PS and MS. For patient AD metrics, the best Pearson correlation (r) and concordance correlation coefficient (ccc) between segmentation methods was found for mean AD (r = 0.94, ccc = 0.92), but worsened as the metric approached the minimum dose (for D90, r = 0.77, ccc = 0.69); BED metrics exhibited a similar trend. Patient PS showed low intra-observer variability (average DSC = 0.81, average MDA = 2.2 mm, average AD/BED metrics within 3.0%).

CONCLUSIONS

⁹⁰Y PET gradient-based segmentation led to accurate/robust results in phantoms, and showed high concordance with MS for reporting mean tumor AD/BED in patients. However, tumor coverage metrics such as D90 exhibited worse concordance between segmentation methods, highlighting the need to standardize segmentation methods when reporting AD/BED metrics from post-therapy ⁹⁰Y PET. Estimated differences in reported AD/BED metrics due to segmentation method will be useful for interpreting RE dosimetry results in the literature including tumor response data.

Treatment of Primary Liver Tumors and Liver Metastases, Part 1: Nuclear Medicine Techniques

⁹⁰Y radioembolization is an increasingly used treatment for both primary and metastatic malignancy in the liver. Understanding the biophysical properties, dosing concerns, and imaging appearance of this treatment is important for interventional radiologists and nuclear medicine physicians to provide important therapy. ⁹⁰Y radioembolization is efficacious and safe, although the possibility of complications does exist. This article provides a comprehensive in-depth discussion about the indications for ⁹⁰Y radioembolization, reviews the role of preprocedural angiography and ^99mTc-macroaggregated albumin scans, illustrates different dosing techniques, compares and contrasts resin and glass microspheres, and describes potential complications.

Fibrolamellar Hepatocellular Carcinoma: Treatment with Yttrium-90 and Subsequent Surgical Resection

We describe a 52-year-old female patient who presented with a 9.5-cm fibrolamellar hepatocellular carcinoma (FL-HCC). The patient was initially unsuitable for surgical resection and therefore underwent transarterial chemoembolization followed by selective internal radiation therapy (SIRT) with Yttrium-90 to downsize the tumour. Following SIRT, the tumour decreased in volume from 350 to 20 cm³ allowing curative (R0) resection with an extended left hepatectomy and reconstruction of IVC. This is the first reported case of FL-HCC treated with SIRT in which, due to the good SIRT response, the patient was downsized to allow curative resection.

Distribution of PEG-coated hollow polyelectrolyte microcapsules after introduction into the circulatory system and muscles of zebrafish

The use of polyelectrolyte multilayer microcapsules as carriers for fluorescent molecular probes is a prospective technique for monitoring the physiological characteristics of animal vasculature and interstitial environment in vivo Polyelectrolyte microcapsules have many features that favor their use as implantable carriers of optical sensors, but little information is available on their interactions with complex living tissues, distribution or residence time following different routes of administration in the body of vertebrates. Using the common fish model, the zebrafish Danio rerio, we studied in vivo the distribution of non-biodegradable microcapsules covered with polyethylene glycol (PEG) over time in the adults and evaluated potential side effects of their delivery into the fish bloodstream and muscles. Fluorescent microcapsules administered into the bloodstream and interstitially (in concentrations that were sufficient for visualization and spectral signal recording) both showed negligible acute toxicity to the fishes during three weeks of observation. The distribution pattern of microcapsules delivered into the bloodstream was stable for at least one week, with microcapsules prevalent in capillaries-rich organs. However, after intramuscular injection, the phagocytosis of the microcapsules by immune cells was manifested, indicating considerable immunogenicity of the microcapsules despite PEG coverage. The long-term negative effects of chronic inflammation were also investigated in fish muscles by histological analysis.

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.

Improved quantitative 90 Y bremsstrahlung SPECT/CT reconstruction with Monte Carlo scatter modeling

PURPOSE

In ⁹⁰ Y microsphere radioembolization (RE), accurate post-therapy imaging-based dosimetry is important for establishing absorbed dose versus outcome relationships for developing future treatment planning strategies. Additionally, accurately assessing microsphere distributions is important because of concerns for unexpected activity deposition outside the liver. Quantitative ⁹⁰ Y imaging by either SPECT or PET is challenging. In ⁹⁰ Y SPECT model based methods are necessary for scatter correction because energy window-based methods are not feasible with the continuous bremsstrahlung energy spectrum. The objective of this work was to implement and evaluate a scatter estimation method for accurate ⁹⁰ Y bremsstrahlung SPECT/CT imaging.

METHODS

Since a fully Monte Carlo (MC) approach to ⁹⁰ Y SPECT reconstruction is computationally very demanding, in the present study the scatter estimate generated by a MC simulator was combined with an analytical projector in the 3D OS-EM reconstruction model. A single window (105 to 195-keV) was used for both the acquisition and the projector modeling. A liver/lung torso phantom with intrahepatic lesions and low-uptake extrahepatic objects was imaged to evaluate SPECT/CT reconstruction without and with scatter correction. Clinical application was demonstrated by applying the reconstruction approach to five patients treated with RE to determine lesion and normal liver activity concentrations using a (liver) relative calibration.

RESULTS

There was convergence of the scatter estimate after just two updates, greatly reducing computational requirements. In the phantom study, compared with reconstruction without scatter correction, with MC scatter modeling there was substantial improvement in activity recovery in intrahepatic lesions (from > 55% to > 86%), normal liver (from 113% to 104%), and lungs (from 227% to 104%) with only a small degradation in noise (13% vs. 17%). Similarly, with scatter modeling contrast improved substantially both visually and in terms of a detectability index, which was especially relevant for the low uptake extrahepatic objects. The trends observed for the phantom were also seen in the patient studies where lesion activity concentrations and lesion-to-liver concentration ratios were lower for SPECT without scatter correction compared with reconstruction with just two MC scatter updates: in eleven lesions the mean uptake was 4.9 vs. 7.1 MBq/mL (P = 0.0547), the mean normal liver uptake was 1.6 vs. 1.5 MBq/mL (P = 0.056) and the mean lesion-to-liver uptake ratio was 2.7 vs. 4.3 (P = 0.0402) for reconstruction without and with scatter correction respectively.

CONCLUSIONS

Quantitative accuracy of ⁹⁰ Y bremsstrahlung imaging can be substantially improved with MC scatter modeling without significant degradation in image noise or intensive computational requirements.

Updated survival outcomes and analysis of long-term survivors from the MORE study on safety and efficacy of radioembolization in patients with unresectable colorectal cancer liver metastases

BACKGROUND

The Metastatic colorectal cancer liver metastases Outcomes after RadioEmbolization (MORE) study was a retrospective analysis of 606 patients with unresectable colorectal liver metastases treated with radioembolization (RE) using ⁹⁰Y-labeled resin microspheres. The first analysis of this study was completed with a last patient follow-up of 77.7 months. We now provide an updated survival analysis through September 15, 2016, with a last patient follow-up of 125 months.

METHODS

⁹⁰Y-RE was considered for patients with advanced liver-only or liver-dominant metastatic colorectal cancer which was deemed not suitable for surgery, ablation, or systemic therapy, and which had progressed or become refractory to at least one line of systemic therapy. All patients with a diagnosis of metastatic colorectal cancer who had received at least 1 RE treatment and 1 follow-up visit were included in the analysis. Patients were treated between July 2002 and December 2011 at one of 11 U.S. tertiary care centers. Data were collected at baseline, on the day of the first ⁹⁰Y-RE treatment (day 0), and at all subsequent visits or until death. Patient medical charts and/or public records were accessed to obtain dates of death.

RESULTS

Dates of death were obtained for 574 out of a total of 606 patients, and overall survival (OS) data analyzed. Updated median OS was 10.0 months (95% CI: 9.2-11.8 months) at a median follow-up of 9.5 months versus the originally reported median OS of 9.6 months (95% CI: 9.0-11.1 months) at a follow-up of 8.6 months in the first MORE analysis. Patients received a median (range) of 2 (0 to 6) lines of chemotherapy. Baseline characteristics and factors significantly associated with patient survival (P<0.01) are consistent with those reported in the first safety analysis of the MORE study. These factors include poor ECOG performance status, markers of advanced disease such as increased extent of tumor-to-target liver involvement, poor baseline liver function, pre-treatment anemia, lung shunt fraction, and number of lines of prior chemotherapy. Patient age did not significantly affect survival outcomes.

CONCLUSIONS

Long-term follow-up confirms that ⁹⁰Y-RE treatment offers favorable survival benefits for patients with unresectable metastatic colorectal cancer, even among patients who received 3 or more prior lines of chemotherapy. Our analysis also supports earlier reported prognostic factors for survival after ⁹⁰Y-RE. Overall, our updated analysis confirms that ⁹⁰Y-RE treatment provided a meaningful response and survival advantage for MORE patients across all ages and across diverse community and academic centers in the U.S.

Liver CT for vascular mapping during radioembolisation workup: comparison of an early and late arterial phase protocol

OBJECTIVES

To compare right gastric (RGA) and segment 4 artery (A4) origin detection rates during radioembolisation workup between early and late arterial phase liver CT protocols.

METHODS

100 consecutive patients who underwent liver CT between May 2012-January 2015 with early or late arterial phase protocol (n = 50 each, 10- vs. 20-s post-threshold delay) were included. RGA/A4 origin detection rates, assessed by two raters, and contrast-to-noise ratio (CNR) of the hepatic artery relative to the portal vein were compared between the protocols.

RESULTS

The first-second rater scored the RGA origin as visible in 58-65 % (specific proportion of agreement 82 %, κ = 0.62); A4 origin in 96-89 % (94 %, κ = 0.54). Thirty-six percent of RGA origins not detectable by DSA were identified on CT. Origin detection rates were not significantly different for early/late arterial phases. Mean CNR was higher in the early arterial phase protocol (1.7 vs. 1.2, p < 0.001).

CONCLUSION

A 10-s delay arterial phase CT protocol does not significantly improve detection of small intra- and extrahepatic branches. RGA origin detection requires further optimization, whereas A4/MHA origin detection is adequate, with good inter-rater reproducibility. CT remains important for preprocedural planning, because it may reveal arterial anatomy not discernible on DSA.

KEY POINTS

• An early arterial phase does not significantly improve RGA and A4/MHA origin detection. • RGA origin detection (58-65 %) on CT is still suboptimal. • 36 % of RGA origins undetectable on DSA can be identified on CT. • A4/MHA origin detection (89-96 %) on CT is excellent. • Inter-rater reproducibility is good for RGA and A4/MHA origin detection on CT.

Radioembolization with 90Y glass microspheres for the treatment of unresectable metastatic liver disease from chemotherapy-refractory gastrointestinal cancers: final report of a prospective pilot study

BACKGROUND

This prospective pilot single-institution study was undertaken to document the feasibility, safety, and efficacy of radioembolization of liver-dominant metastatic gastrointestinal cancer using ⁹⁰Y glass microspheres.

METHODS

Between June 2010 and October 2013, 42 adult patients (26 men, 16 women; median age 60 years) with metastatic chemotherapy-refractory unresectable colorectal (n=21), neuroendocrine (n=11), intrahepatic bile duct (n=7), pancreas (n=2), and esophageal (n=1) carcinomas underwent 60 lobar or segmental administrations of ⁹⁰Y glass microspheres. Data regarding clinical and laboratory adverse events (AE) were collected prospectively for up to 5.5 years after radioembolization. Radiographic responses were evaluated using Response Evaluation Criteria in Solid Tumors (RECIST), version 1.1. Time to maximum response, response duration, progression-free survival (PFS) (hepatic and extrahepatic), and overall survival (OS) were measured.

RESULTS

Median target dose and activity were 109.4 Gy and 2.6 GBq per treatment session, respectively. Majority of clinical AE were grade 1 or 2 in severity. Patients with colorectal cancer had hepatic objective response rate (ORR) of 25% and a hepatic disease control rate (DCR) of 80%. Median PFS and OS were 1.0 and 4.4 months, respectively. Patients with neuroendocrine tumors (NET) had hepatic ORR and DCR of 73% and 100%, respectively. Median PFS was 8.9 months for this cohort. DCR and median PFS and OS for patients with cholangiocarcinoma were 86%, 1.1 months, and 6.7 months, respectively.

CONCLUSIONS

⁹⁰Y glass microspheres device has a favorable safety profile, and achieved prolonged disease control of hepatic tumor burden in a subset of patients, including all patients enrolled in the neuroendocrine cohort.

Synthetic nanoparticles for delivery of radioisotopes and radiosensitizers in cancer therapy

Radiotherapy has been, and will continue to be, a critical modality to treat cancer. Since the discovery of radiation-induced cytotoxicity in the late 19th century, both external and internal radiation sources have provided tremendous benefits to extend the life of cancer patients. Despite the dramatic improvement of radiation techniques, however, one challenge persists to limit the anti-tumor efficacy of radiotherapy, which is to maximize the deposited dose in tumor while sparing the rest of the healthy vital organs. Nanomedicine has stepped into the spotlight of cancer diagnosis and therapy during the past decades. Nanoparticles can potentiate radiotherapy by specifically delivering radionuclides or radiosensitizers into tumors, therefore enhancing the efficacy while alleviating the toxicity of radiotherapy. This paper reviews recent advances in synthetic nanoparticles for radiotherapy and radiosensitization, with a focus on the enhancement of in vivo anti-tumor activities. We also provide a brief discussion on radiation-associated toxicities as this is an area that, up to date, has been largely missing in the literature and should be closely examined in future studies involving nanoparticle-mediated radiosensitization.

Administered activity and outcomes of glass versus resin (90)Y microsphere radioembolization in patients with colorectal liver metastases

BACKGROUND

Given the differences in size, specific activity, and dosing methods for glass yttrium-90 microspheres ((90)Y-glass) and resin (90)Y microspheres ((90)Y-resin), these therapies may expose the liver to different amounts of radiation, thereby affecting their efficacy and tolerability. We aimed to compare the prescribed activity of (90)Y-glass and (90)Y-resin for real-world patients undergoing selective internal radiation therapy (SIRT) for liver-dominant metastatic colorectal cancer (mCRC) and to assess efficacy and safety outcomes in these patients.

METHODS

We examined the records of 28 consecutive patients with unresectable colorectal liver metastases treated with SIRT between June 2008 and May 2011 at our institution. Using baseline CT and MR images, we calculated a projected activity as if we had used the other product and compared it to the actual prescribed activity of (90)Y-glass and (90)Y-resin for each SIRT treatment per manufacturer guidelines. Progression and adverse events were evaluated at follow up visits. Survival was analyzed by the Kaplan-Meier method.

RESULTS

For (90)Y-glass treatments with a mean prescribed (90)Y activity of 1.77 GBq, the mean projected (90)Y-resin activity was 0.84 GBq. For (90)Y-resin treatments with a mean prescribed (90)Y activity of 1.05 GBq, the mean projected (90)Y-glass activity was 2.48 GBq. The median survival was 9.3 months versus 18.2 months for (90)Y-glass and (90)Y-resin, respectively (P=0.292). During the second year after SIRT, the hazard ratio of death for patients treated with (90)Y-glass versus (90)Y-resin was 4.0 (95% CI: 1.3, 12.3; P=0.017). No significant difference in progression, adverse events or liver toxicity was observed.

CONCLUSIONS

Using manufacturer recommended guidelines, (90)Y-resin delivers significantly less activity than (90)Y-glass to patients with liver-dominant mCRC undergoing SIRT with no significant difference in adverse events and a trend toward improved survival.

Hepatopulmonary Shunting: A Prognostic Indicator of Survival in Patients with Metastatic Colorectal Adenocarcinoma Treated with 90Y Radioembolization

Purpose To determine if high lung shunt fraction (LSF) is an independent prognostic indicator of poor survival in patients who undergo yttrium 90 radioembolization for unresectable liver-dominant metastatic colorectal cancer. Materials and Methods Retrospective data were analyzed from 606 patients (62% men; mean age, 62 years) who underwent radioembolization to treat liver metastases from colorectal adenocarcinoma between July 2002 and December 2011 at 11 U.S. centers. Institutional review board exemptions were granted prior to the collection of data at each site. Overall survival was estimated by using Kaplan-Meier survival and univariate Cox proportional hazards models to examine the effect of LSF on survival and to compare this to other potential prognostic indicators. Multivariate analysis was also performed to determine whether LSF is an independent risk factor for poor survival. Results LSF higher than 10% was predictive of significantly decreased survival (median, 6.9 months vs 10.0 months; hazard ratio, 1.60; P < .001) and demonstrated a mild but significant correlation to serum carcinoembryonic antigen levels and tumor-to-liver volume ratio (Pearson correlation coefficients, 0.105 and 0.113, respectively; P < .05). A progressive decrease in survival was observed as LSF increased from less than 5% to more than 20% (P < .05). LSF did not correlate with the presence of extrahepatic metastases or prior administration of bevacizumab. Conclusion Increased LSF is an independent prognostic indicator of worse survival in patients undergoing radioembolization for liver-dominant metastatic colorectal adenocarcinoma. High LSF correlates poorly to other potential markers of tumor size, such as tumor-to-liver volume ratio or serum carcinoembryonic antigen level, and does not correlate to the presence of extrahepatic metastases. ^© RSNA, 2016 Online supplemental material is available for this article.

Yttrium-90 Selective Internal Radiation Therapy with Glass Microspheres for Hepatocellular Carcinoma: Current and Updated Literature Review

Hepatocellular carcinoma is the most common primary liver cancer and it represents the majority of cancer-related deaths in the world. More than 70% of patients present at an advanced stage, beyond potentially curative options. Ytrrium-90 selective internal radiation therapy (Y90-SIRT) with glass microspheres is rapidly gaining acceptance as a potential therapy for intermediate and advanced stage primary hepatocellular carcinoma and liver metastases. The technique involves delivery of Y90 infused glass microspheres via the hepatic arterial blood flow to the appropriate tumor. The liver tumor receives a highly concentrated radiation dose while sparing the healthy liver parenchyma due to its preferential blood supply from portal venous blood. There are two commercially available devices: TheraSphere® and SIR-Spheres®. Although, Y90-SIRT with glass microspheres improves median survival in patients with intermediate and advanced hepatocellular carcinoma and has the potential to downstage hepatocellular carcinoma so that the selected candidates meet the transplantable criteria, it has not gained widespread acceptance due to the lack of large randomized controlled trials. Currently, there are various clinical trials investigating the use of Y90-SIRT with glass microspheres for treatment of hepatocellular carcinoma and the outcomes of these trials may result in the incorporation of Y90-SIRT with glass microspheres into the treatment guidelines as a standard therapy option for patients with intermediate and advanced stage hepatocellular carcinoma.

Evidence-based medical oncology and interventional radiology paradigms for liver-dominant colorectal cancer metastases

Colorectal cancer metastasizes predictably, with liver predominance in most cases. Because liver involvement has been shown to be a major determinant of survival in this population, liver-directed therapies are increasingly considered even in cases where there is (limited) extrahepatic disease. Unfortunately, these patients carry a known risk of recurrence in the liver regardless of initial therapy choice. Therefore, there is a demand for minimally invasive, non-surgical, personalized cancer treatments to preserve quality of life in the induction, consolidation, and maintenance phases of cancer therapy. This report aims to review evidence-based conceptual, pharmacological, and technological paradigm shifts in parenteral and percutaneous treatment strategies as well as forthcoming evidence regarding next-generation systemic, locoregional, and local treatment approaches for this patient population.

Extending the Frontiers Beyond Thermal Ablation by Radiofrequency Ablation: SBRT, Brachytherapy, SIRT (Radioembolization)

Metastatic spread of the primary is still defined as the systemic stage of disease in treatment guidelines for various solid tumors. This definition is the rationale for systemic therapy. Interestingly and despite the concept of systemic involvement, surgical resection as a local treatment has proven to yield long-term outcomes in a subset of patients with limited metastatic disease, supporting the concept of oligometastatic disease. Radiofrequency ablation has yielded favorable outcomes in patients with hepatocellular carcinoma and colorectal metastases, and some studies indicate its prognostic potential in combined treatments with systemic therapies. However, some significant technical limitations apply, such as size limitation, heat sink effects, and unpredictable heat distribution to adjacent risk structures. Interventional and non-invasive radiotherapeutic techniques may overcome these limitations, expanding the options for oligometastatic patients and cytoreductive concepts. Current data suggest very high local control rates even in large tumors at any given location in the human body. The article focusses on the characteristics and possibilities of stereotactic body radiation therapy, interstitial high-dose-rate brachytherapy, and Yttrium-90 radioembolization. In this article, we discuss the differences of the technical preferences as well as their impact on indications. Current data is presented and discussed with a focus on application in oligometastatic or cytoreductive concepts in different tumor biologies.

Innovation in catheter design for intra-arterial liver cancer treatments results in favorable particle-fluid dynamics

Background

Liver tumors are increasingly treated with radioembolization. Here, we present first evidence of catheter design effect on particle-fluid dynamics and downstream branch targeting during microsphere administrations.

Materials and methods

A total of 7 experiments were performed in a bench-top model of the hepatic arterial vasculature with recreated hemodynamics. Fluorescent microspheres and clinically used holmium microspheres were administered with a standard microcatheter (SMC) and an anti-reflux catheter (ARC) positioned at the same level along the longitudinal vessel axis. Catheter-related particle flow dynamics were analyzed by reviewing video recordings of UV-light illuminated fluorescent microsphere administrations. Downstream branch distribution was analyzed by quantification of collected microspheres in separate filters for two first-order branches. Mean deviation from a perfectly homogenous distribution (DHD) was used to compare the distribution homogeneity between catheter types.

Results

The SMC administrations demonstrated a random off-centered catheter position (in 71 % of experiments), and a laminar particle flow pattern with an inhomogeneous downstream branch distribution, dependent on catheter position and injection force. The ARC administrations demonstrated a fixed centro-luminal catheter position, and a turbulent particle flow pattern with a more consistent and homogenous downstream branch distribution. Quantitative analyses confirmed a significantly more homogeneous distribution with the ARC; the mean DHD was 40.85 % (IQR 22.76 %) for the SMC and 15.54 % (IQR 6.46 %) for the ARC (p = 0.047).

Conclusion

Catheter type has a significant impact on microsphere administrations in an in-vitro hepatic arterial model. A within-patient randomized controlled trial has been initiated to investigate clinical catheter-related effects during radioembolization treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-015-0188-8) contains supplementary material, which is available to authorized users.

A review of 3D image-based dosimetry, technical considerations and emerging perspectives in 90Y microsphere therapy

Yttrium-90 radioembolization (⁹⁰Y-RE) is a well-established therapy for the treatment of hepatocellular carcinoma (HCC) and also of metastatic liver deposits from other malignancies. Nuclear Medicine and Cath Lab diagnostic imaging takes a pivotal role in the success of the treatment, and in order to fully exploit the efficacy of the technique and provide reliable quantitative dosimetry that are related to clinical endpoints in the era of personalized medicine, technical challenges in imaging need to be overcome. In this paper, the extensive literature of current ⁹⁰Y-RE techniques and challenges facing it in terms of quantification and dosimetry are reviewed, with a focus on the current generation of 3D dosimetry techniques. Finally, new emerging techniques are reviewed which seek to overcome these challenges, such as high-resolution imaging, novel surgical procedures and the use of other radiopharmaceuticals for therapy and pre-therapeutic planning.