90Y-PET/CT-based dosimetry after selective internal radiation therapy predicts outcome in patients with liver metastases from colorectal cancer

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

BACKGROUND

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

MATERIALS/METHODS

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

RESULTS

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

CONCLUSION

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

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION

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

ADVANCES IN KNOWLEDGE

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

Characterizing the voxel-based approaches in radioembolization dosimetry with reDoseMC

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Evaluating therapeutic efficacy of extended shelf-life 90 Y glass microspheres in transarterial radioembolization for colorectal cancer: a quantitative FDG PET/CT analysis

OBJECTIVES

There is a lack of sufficient evidence regarding the use of extended shelf-life (ExSL) Yttrium-90 ( 90 Y) glass radiomicrospheres in metastatic colorectal cancer (mCRC) patients. We aimed to investigate the efficacy of ExSL 90 Y glass radiomicrospheres with a personalized treatment approach by analyzing 18 F-FDG PET/CT quantitative parameters [metabolic tumor volume (MTV) and total lesion glycolysis (TLG)] separately before and after the treatment.

METHODS

A total of 93 radioembolization sessions involving 77 patients were included. Simplicit 90 Y software was utilized to perform multicompartmental voxel-based dosimetry. Adverse events were recorded using the CTCAE v5.0 criteria. The survival data were recorded in detail.

RESULTS

The overall disease control rate was 84.9%, with a median overall survival (OS) of 12.7 months and median progression-free survival (PFS) of 8.3 months. A statistically significant increase in treatment response rate was observed when there was an increase in absorbed tumor dose for pre-treatment unit MTV ( P  = 0.005) and TLG ( P  = 0.004) values. We didn't observe any additional side effects/vital risks that could be considered clinically significant.

CONCLUSION

Our study has provided evidence on the therapeutic effectiveness and safety in terms of dose-toxicity profile of ExSL 90 Y glass microspheres in a large cohort of mCRC patients. With a personalized treatment approach, the increase in radiation dose absorbed by the tumor has shown a significant contribution to treatment response rate, as indicated by quantitative measurements obtained through 18 F-FDG PET/CT.

Predictive Partition Dosimetry and Outcomes after Yttrium-90 Resin Microsphere Radioembolization of Colorectal Cancer Metastatic to the Liver: A Retrospective Analysis

PURPOSE

To characterize estimated absorbed tumor dose (ADT), objective response (OR), and estimated target dose of liver metastatic colorectal cancer (mCRC) after resin microsphere yttrium-90 (90Y) radioembolization using partition dosimetry.

MATERIALS AND METHODS

In this retrospective, single-center study, multicompartment dosimetry of index tumors undergoing 90Y radioembolization from October 2013 to July 2022 was performed using MIM SurePlan and pretreatment technetium-99m macroaggregated albumin infusion data. Thirty-eight patients with mCRC underwent treatments for 59 index tumors. Patients were imaged every 2-3 months after treatment and then every 3-6 months after disease control to determine the best response per Response Evaluation Criteria in Solid Tumors 1.1. Responses were categorized as OR or nonresponse (NR). A Cox proportional hazards model evaluated the probability of tumor OR and local progression-free survival (LPFS) based on ADT.

RESULTS

Patients had a median follow-up of 116 days (interquartile range [IQR], 69-231 days). The ADT was higher for OR patients than for NR patients (median, 130.8 [IQR, 85.6-239.0] vs 40.6 [IQR, 26.0-66.3] Gy; P < .001). A greater percentage of OR than NR patients were treated with activities calculated by partition modeling (54% vs 12%; P = .005). Only ADT predicted response (P = .032). At 6 months, an ADT of 120 Gy predicted a 55% (95% CI, 0.0%-89%) probability of OR. Only ADT (P = .010) and female sex (P = .014) predicted LPFS. At 1 year, an ADT of 120 Gy predicted a 70% (95% CI, 35%-100%) probability of LPFS.

CONCLUSIONS

Tumor dose was the strongest predictor of OR for mCRC. Administration of an estimated 120 Gy to mCRC predicted 55% OR with 90Y resin microspheres at 6 months.

Radioembolisation of liver metastases

This review aims to present contemporary data for SIRT in the treatment of secondary hepatic malignancies including colorectal, neuroendocrine, breast and uveal melanoma.

Update on Locoregional Therapies for Cholangiocellular Carcinoma

Locoregional therapy options for CCA are used, in particular, for non-resectable tumors and aim to reduce tumor viability or delay tumor growth and ultimately prolong overall survival. In addition to local ablative procedures such as radiofrequency- or microwave-ablation, transarterial procedures such as transarterial embolization (TAE), transarterial chemoembolization (TACE), or selective internal radiotherapy (SIRT) play a major role. In particular, in combination with advances in molecular medicine and immunotherapy, there has been a further development in the therapy of primary malignant liver tumors in recent years. In this review, we analyze data from recent studies and examine the implications for therapy of CCA, particularly with regard to the combination of locoregional therapies with modern systemic therapies.

Prognostic Factors for Effectiveness Outcomes After Transarterial Radioembolization in Metastatic Colorectal Cancer: Results From the Multicentre Observational Study CIRT

BACKGROUND

Transarterial radioembolisation (TARE) with Yttrium-90 resin microspheres is a treatment option for patients with metastatic colorectal cancer in the liver (mCRC). A better understanding of the prognostic factors and treatment application can improve survival outcomes.

METHODS

We analysed the safety and effectiveness of 237 mCRC patients included in the prospective observational study CIRSE Registry for SIR-Spheres Therapy (CIRT) for independent prognostic factors for overall survival (OS), progression-free survival (PFS) and hepatic progression-free survival (hPFS) using the Cox proportional-hazard model.

RESULTS

The median OS was 9.8 months, median PFS was 3.4 months and median hPFS was 4.2 months. Independent prognostic factors for an improved overall survival were the absence of extra-hepatic disease (P= .0391), prior locoregional procedures (P= .0037), an Aspartate transaminase to Platelet Ratio Index (APRI) value of ≤0.40 (P< .0001) and International Normalized Ratio (INR) ≤1 (P= .0078). Partition model dosimetry resulted in improved OS outcomes compared to the body surface area model (P = .0120). Independent predictors for PFS were APRI >0.40 (P = .0416) and prior ablation (P = .0323), and for hPFS these were 2 to 5 tumor nodules (P = .0148), Albumin-bilirubin (ALBI) grade 3 (P = .0075) and APRI >0.40 (P = .0207). During the study, 95 of 237 (40.1%) patients experienced 197 adverse events, with 28 of 237 (11.8%) patients having a grade 3 or higher adverse events.

CONCLUSION

Including easy-to-acquire laboratory markers INR, APRI, ALBI and using partition model dosimetry can identify mCRC patients that may benefit from TARE.

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

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

Trans-arterial Radioembolization Dosimetry in 2022

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

TCP post-radioembolization and TCP post-EBRT in HCC are similar and can be predicted using the in vitro radiosensitivity

Background

Tumor equivalent uniform dose (EUD) is proposed as a predictor of patient outcome after liver radioembolization (RE) of hepatocellular carcinoma (HCC) and can be evaluated with ⁹⁰Y-TOF-PET. The aim is to evaluate the correlation between PET-based tumors EUD and the clinical response evaluated with dual molecular tracer (¹¹C-acetate and ¹⁸F-FDG) PET/CT post-RE.

Methods

34 HCC tumors in 22 patients were prospectively evaluated. The metabolic response was characterized by the total lesion metabolism variation (ΔTLM) between baseline and follow-up. This response allowed to compute a tumor control probability (TCP) as a function of the tumor EUD.

Results

The absorbed dose response correlation was highly significant (R = 0.72, P < 0.001). With an absorbed dose threshold of 40 Gy, the metabolic response was strongly different in both groups (median response 35% versus 100%, P < 0.001). Post-RE TCP as a function of the EUD was very similar to that observed in external beam radiation therapy (EBRT), with TCP values equal to 0.5 and 0.95 for a EUD of 51 Gy and 100 Gy, respectively. The TCP was perfectly predicted by the Poisson model assuming an inter tumor radiosensitivity variation of 30% around the HCC cell in vitro value.

Conclusions

EUD-based ⁹⁰Y TOF-PET/CT predicts the metabolic response post-RE in HCC assessed using dual molecular PET tracers and provides a similar TCP curve to that observed in EBRT. In vivo and in vitro HCC radiosensitivities are similar. Both TCPs show that a EUD of 100 Gy is needed to control HCC for the three devices (resin spheres, glass spheres, EBRT). Observed absorbed doses achieving this 100 Gy-EUD ranged from 190 to 1800 Gy!

Supplementary Information

The online version contains supplementary material available at 10.1186/s13550-022-00911-0.

Development of a scatter correction technique for planar 99mTc-MAA imaging to improve accuracy in lung shunt fraction estimation

PURPOSE

Prior to ⁹⁰Y selective internal radiation therapy (SIRT) treatment, ^99mTc-MAA scintigraphy imaging is used in the estimation of the lung shunt fraction (LSF). Planar imaging is recommended for determining a LSF ratio. However, the estimate may be affected by scatter contributions, attenuation and respiratory motion. The objective of this study was to correct for the effects of scatter in the LSF, towards the determination of a more accurate estimation method of LSF derived from planar scintigraphy imaging, which is recommended by international guidelines.

METHODS

The open access SIMIND Monte Carlo modelling software was used to estimate an optimum scatter window (SW) for scatter correction. The uncertainties associated with scatter and scatter contributions from the liver on the LSF were evaluated using an anthropomorphic thorax phantom and a virtual Vox-Man phantom. A brief retrospective examination of patient scans and tumour location investigated the impact that the inclusion of the simulated scatter corrections had on the LSF estimation.

RESULTS

The percentage overestimation of the manufacturer recommended method of LSF estimation was 192%. SW corrections improved the uncertainty to within 19% for the range of known LSFs. Similar findings were observed for our patient and tumour location studies.

CONCLUSION

The incorporated scatter corrections can significantly improve the accuracy of the LSF estimation, thereby providing a robust gamma camera, patient and tumour depth specific correction which is easily implementable. This is supported by Monte Carlo, phantom and preliminary patient studies.

Radioembolization, Principles and indications

Radioembolization is the selective application of radionuclide-loaded microspheres into liver arteries for the therapy of liver tumours and metastases. In this review, we focused on therapy planning and dosimetry, as well as the main indications of 90Y-glass and resin microspheres and 166Ho-microspheres.

Organ-level internal dosimetry for intra-hepatic-arterial administration of 99m Tc-macroaggregated albumin

PURPOSE

There are no published data on organ doses following intra-hepatic-arterial administration of ^99m Tc-macroaggregated-albumin (IHA ^99m Tc-MAA) routinely used in ⁹⁰ Y-radioembolization-treatment planning to assess intra- and extra-hepatic depositions and calculate lung-shunt-fraction (LSF). We propose a method to model the organ doses following IHA ^99m Tc-MAA that incorporates three in vivo constituent biodistributions, the ^99m Tc-MAA that escape the liver due to LSF, and the ^99m Tc-MAA disassociation fraction (DF).

METHODS

The potential in vivo biodistributions for IHA ^99m Tc-MAA are: Liver-Only MAA with all activity sequestered in the liver (LSF = 0&DF = 0), Intravenous MAA with all activity transferred intravenously as ^99m Tc-MAA (LSF = 1&DF = 0), and Intravenous Pertechnetate with all activity is transferred intravenously as ^99m Tc-pertechnetate (LSF = 0&DF = 1). Organ doses for Liver-Only MAA were determined using OLINDA/EXM 2.2, where liver was modeled as the source organ containing ^99m Tc-MAA, while those for Intravenous MAA and Intravenous Pertechnetate were from ICRP 128. Organ doses for the general case can be determined as a weighted-linear-combination of the three constituent biodistributions depending on the LSF and DF. The maximum-dose scenario was modeled by selecting the highest dose rate for each organ amongst the three constituent cases.

RESULTS

For Liver-Only MAA, the liver as source organ received the highest dose at 98.6 and 126 mGy/GBq for the Adult Male and Adult Female phantoms, respectively; all remaining organs received <27 and <32 mGy/GBq. For Intravenous MAA, the lung as source organ received the highest dose at 66 and 97 mGy/GBq; all remaining organs received <16 and <21 mGy/GBq. The organ with the highest dose for Intravenous Pertechnetate was the upper-large-intestinal wall at 56 and 73 mGy/GBq; all remaining organs received <26 and <34 mGy/GBq. The liver and lung doses for the maximum-dose scenario with 5 mCi (185 MBq) ^99m Tc-MAA were estimated at 18.2 and 12.2 mGy, and 23.3 and 17.9 mGy, for the Adult Male and Adult Female phantoms, respectively.

CONCLUSION

Organ dose estimates following IHA ^99m Tc-MAA based on constituent biodistribution models and patient-specific LSF and DF values have been derived. Liver and lung were the organs with highest dose, receiving at most 15 - 25 mGy in the maximum-dose scenario, following 5 mCi IHA ^99m Tc-MAA. This article is protected by copyright. All rights reserved.

Efficacy of voxel-based dosimetry map for predicting response to trans-arterial radioembolization therapy for hepatocellular carcinoma: a pilot study

OBJECTIVE

Typical clinical dosimetry models for trans-arterial radioembolization (TARE) assume uniform dose distribution in each tissue compartment. We performed simple voxel-based dosimetry using post-treatment 90Y PET following TARE with 90Y-resin microspheres and investigated its prognostic value in a pilot cohort.

METHOD

Ten patients with 14 hepatocellular carcinoma lesions who underwent TARE with 90Y-resin microspheres were retrospectively included. The partition model-based expected target tumor dose (TDp) was calculated using a pretreatment 99mTc-macroaggregated albumin scan. From post-treatment 90Y-microsphere PET and voxel-wise S-value kernels, voxel-based dose maps were produced and the absorbed dose of each lesion (TDv) was calculated. Heterogeneity of intratumoral absorbed doses was assessed using the SD and coefficient of variation of voxel doses. The response of each lesion was determined based on contrast-enhanced MRI or CT, or both. Lesion responses were classified as local control success or failure. Prognostic values of dosimetry parameters and clinicopathological factors were evaluated in terms of progression-free survival (PFS) of each lesion.

RESULTS

TDv was significantly different between local control success and failure groups, whereas tumor size, TDp and intratumoral dose heterogeneity were not. Univariate survival analysis identified serum aspartate transaminase level ≥40 IU/L, tumor size ≥66 mm and TDv <81 Gy as significant prognostic factors for PFS. However, only TDv was an independent predictive factor in the multivariate analysis (P = 0.022). There was a significant correlation between TDv and PFS (P = 0.009; r = 0.669).

CONCLUSIONS

In TARE, voxel-based dose index TDv can be estimated on post-treatment 90Y PET using a simple method. TDv was a more effective prognostic factor for TARE than TDp and clinicopathologic factors in this pilot study. Further studies are warranted on the role of voxel-based dose and dose distribution in TARE.

Role of Resin Microsphere Y90 Dosimetry in Predicting Objective Tumor Response, Survival and Treatment Related Toxicity in Surgically Unresectable Colorectal Liver Metastasis: A Retrospective Single Institution Study

Simple Summary

Colorectal liver metastases are difficult to treat, with only a minority of patients eligible for surgical resection. Yttrium-90 selective internal radiation therapy is an alternative treatment currently used for patients who have progressed on chemotherapy. A technique called dosimetry allows clinicians to analyze how much radiation was delivered to target lesions post-treatment. The aim of this study is to evaluate the relationship of various dosimetric parameters with objective tumor response, overall survival, and treatment related toxicity with the potential goal of optimizing Yttrium-90 treatment in this patient population. Additionally, other potential predictors of survival outcomes, including clinical and demographic factors, were also evaluated. We found that delivering a mean tumor dose ≥100 Gy when using resin microspheres was significantly associated with objective tumor response and prolonged overall survival. In this study, no mean non-tumoral liver dose threshold was found to predict treatment related toxicity.

Abstract

Purpose: To Evaluate the correlation between tumor dosimetric parameters with objective tumor response (OR) and overall survival (OS) in patients with surgically unresectable colorectal liver metastasis (CRLM) undergoing resin-based Ytrrium-90 selective internal radiation therapy (Y90 SIRT). Materials and Methods: 45 consecutive patients with CRLM underwent resin-based Y90 SIRT in one or both hepatic lobes (66 treated lobes total). Dose volume histograms were created with MIM Sureplan^® v.6.9 using post-treatment SPECT/CT. Dosimetry analyses were based on the cumulative volume of the five largest tumors in each treatment session and non-tumoral liver (NTL) dose. Receiver operating characteristic (ROC) curve was used to evaluate tumor dosimetric factors in predicting OR by Response Evaluation Criteria for Solid Tumors at 3 months post-Y90. Additionally, ROC curve was used to evaluate non-tumoral liver dose as a predictor of grade ≥ 3 liver toxicity and radioembolization induced liver disease (REILD) 3 months post Y90. To minimize for potential confounding demographic and clinical factors, univariate and multivariate analysis of survival with mean tumor dose as one of the factors were also performed. Kaplan-Meier estimation was used for OS analysis from initial Y90 SIRT. Results: 26 out of 45 patients had OR with a median OS of 17.2 months versus 6.8 months for patients without OR (p < 0.001). Mean tumor dose (TD) of the five largest tumors was the strongest predictor of OR with an area under the curve of 0.73 (p < 0.001). Minimum TD, and TD to 30%, 50%, and 70% of tumor volume also predicted OR (p’s < 0.05). Mean TD ≥ 100 Gy predicted a significantly prolonged median OS of 19 vs. 11 months for those receiving TD < 100 Gy (p = 0.016). On univariate analysis, mean TD < 100 Gy, presence of any genomic mutation, presence of MAPK pathway mutation, bilobar hepatic metastases and diffuse metastatic disease (>10 lesions per liver lobe) were found to be predictors of shorter median OS. On multivariate analysis, mean TD < 100 Gy, presence of any genomic mutation, and diffuse hepatic metastatic disease were found to be independent predictors of shorter OS. Overall, six (13.3%) patients developed grade ≥ 3 liver toxicity post Y90 of whom two (4.4%) patients developed REILD. No dose threshold predicting grade ≥ 3 liver toxicity or REILD was identified. Conclusions: Mean TD ≥ 100 Gy in patients with unresectable CRLM undergoing resin-based Y90 SIRT predicts OR and prolonged OS.

Individualised dosimetry and safety of SIRT for intrahepatic cholangiocarcinoma

Background

The aim of this study was to investigate the safety and efficacy of selective internal radiation therapy (SIRT) with ⁹⁰Y resin microspheres for the treatment of Intrahepatic Cholangiocarcinoma (ICC). A total of 23 SIRT procedures from 18 ICC subjects were analysed to determine a lesion-based dose/response relationship with absorbed dose measures from ⁹⁰Y PET and metabolic response as measured on [¹⁸F]FDG PET. Average absorbed dose (D_avg), minimum dose to 70% of the volume (D₇₀), volume receiving at least 50 Gy (V₅₀), biological effective dose (BED) and equivalent uniform dose (EUD), were compared to changes in metabolic volume, maximum standardised uptake value (SUV_max) and total lesion glycolysis (TLG). Dose to normal liver was assessed with changes in liver uptake rate as measured with [^99mTc]mebrofenin scintigraphy for a cohort of 20 subjects with primary liver malignancy (12 ICC, 8 hepatocellular carcinoma (HCC)).

Results

Thirty-four lesions were included in the analysis. A relationship was found between metabolic response and both D_avg and EUD similar to that seen previously in metastatic colorectal cancer (mCRC), albeit trending towards a lower response plateau. Both dose and SUV coefficient of variation within the lesion (CoV_dose and CoV_SUV), baseline TLG and EUD were found to be mildly significant predictors of response. No strong correlation was seen between normal liver dose and change in [^99mTc]mebrofenin liver uptake rate; low baseline uptake rate was not indicative of declining function following SIRT, and no subjects dropped into the ‘poor liver function’ category.

Conclusions

ICC lesions follow a similar dose–response trend as mCRC, however, despite high lesion doses a full metabolic response was rarely seen. The CoV of lesion dose may have a significant bearing on response, and EUD correlated more tightly with metabolic response compared to D_avg. SIRT in primary liver malignancy appears safe in terms of not inducing a clinically significant decline in liver function, and poor baseline uptake rate is not predictive of a reduction in function post SIRT.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40658-021-00406-2.

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

PURPOSE

A multidisciplinary expert panel convened to formulate state-of-the-art recommendations for optimisation of selective internal radiation therapy (SIRT) with yttrium-90 (90Y)-resin microspheres.

METHODS

A steering committee of 23 international experts representing all participating specialties formulated recommendations for SIRT with 90Y-resin microspheres activity prescription and post-treatment dosimetry, based on literature searches and the responses to a 61-question survey that was completed by 43 leading experts (including the steering committee members). The survey was validated by the steering committee and completed anonymously. In a face-to-face meeting, the results of the survey were presented and discussed. Recommendations were derived and level of agreement defined (strong agreement ≥ 80%, moderate agreement 50%-79%, no agreement ≤ 49%).

RESULTS

Forty-seven recommendations were established, including guidance such as a multidisciplinary team should define treatment strategy and therapeutic intent (strong agreement); 3D imaging with CT and an angiography with cone-beam-CT, if available, and 99mTc-MAA SPECT/CT are recommended for extrahepatic/intrahepatic deposition assessment, treatment field definition and calculation of the 90Y-resin microspheres activity needed (moderate/strong agreement). A personalised approach, using dosimetry (partition model and/or voxel-based) is recommended for activity prescription, when either whole liver or selective, non-ablative or ablative SIRT is planned (strong agreement). A mean absorbed dose to non-tumoural liver of 40 Gy or less is considered safe (strong agreement). A minimum mean target-absorbed dose to tumour of 100-120 Gy is recommended for hepatocellular carcinoma, liver metastatic colorectal cancer and cholangiocarcinoma (moderate/strong agreement). Post-SIRT imaging for treatment verification with 90Y-PET/CT is recommended (strong agreement). Post-SIRT dosimetry is also recommended (strong agreement).

CONCLUSION

Practitioners are encouraged to work towards adoption of these recommendations.

To 1000 Gy and back again: a systematic review on dose-response evaluation in selective internal radiation therapy for primary and secondary liver cancer

Purpose

To systematically review all current evidence into the dose-response relation of yttrium-90 and holmium-166 selective internal radiation therapy (SIRT) in primary and secondary liver cancer.

Methods

A standardized search was performed in PubMed (MEDLINE), Embase, and the Cochrane Library in order to identify all published articles on dose-response evaluation in SIRT. In order to limit the results, all articles that investigated SIRT in combination with other therapy modalities (such as chemotherapy) were excluded.

Results

A total of 3038 records were identified of which 487 were screened based on the full text. Ultimately, 37 studies were included for narrative analysis. Meta-analysis could not be performed due to the large heterogeneity in study and reporting designs. Out of 37 studies, 30 reported a ‘mean dose threshold’ that needs to be achieved in order to expect a response. This threshold appears to be higher for hepatocellular carcinoma (HCC, 100–250 Gy) than for colorectal cancer metastases (CRC, 40–60 Gy). Reported thresholds tend to be lower for resin microspheres than when glass microspheres are used.

Conclusion

Although the existing evidence demonstrates a dose-response relationship in SIRT for both primary liver tumours and liver metastases, many pieces of the puzzle are still missing, hampering the definition of standardized dose thresholds. Nonetheless, most current evidence points towards a target mean dose of 100–250 Gy for HCC and 40–60 Gy for CRC. The field would greatly benefit from a reporting standard and prospective studies designed to elucidate the dose-response relation in different tumour types.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-021-05340-0.

The joint use of 99mTc-MAA-SPECT/CT and cone-beam CT optimizes radioembolization planning

Purpose

To determine which imaging method used during radioembolization (RE) work-up: contrast-enhanced computed tomography (CECT), ^99mTc-MAA-SPECT/CT or cone beam-CT (CBCT), more accurately predicts the final target volume (TgV) as well as the influence that each modality has in the dosimetric calculation.

Methods

TgVs from ^99mTc-MAA-SPECT/CT, CECT and CBCT were consecutively obtained in 24 patients treated with RE and compared with ⁹⁰Y PET/CT TgV. Using the TgVs estimated by each imaging modality and a fictitious activity of 1 GBq, the corresponding absorbed doses by tumor and non-tumoral parenchyma were calculated for each patient. The absorbed doses for each modality were compared with the ones obtained using ⁹⁰Y PET/CT TgV.

Results

^99mTc-MAA-SPECT/CT predicted ⁹⁰Y PET/CT TgV better than CBCT or CECT, even for selective or superselective administrations. Likewise, ^99mTc-MAA-SPECT/CT showed dosimetric values more similar to those obtained with ⁹⁰Y PET/CT. Nevertheless, CBCT provided essential information for RE planning, such as ensuring the total coverage of the tumor and, in cases with more than one feeding artery, splitting the activity according to the volume of tumor perfused by each artery.

Conclusion

The joint use of ^99mTc-MAA-SPECT/CT and CBCT optimizes dosimetric planning for RE procedures, enabling a more accurate personalized approach.

Dose-response for yttrium-90 resin microsphere radioembolisation

The fundamental premise of yttrium-90 radioembolisation is to balance safety with efficacy. To achieve this, dose-response guidance must be provided. This is a tabulation of published data of key dose-response metrics for yttrium-90 resin microsphere radioembolisation of liver malignancies. Metrics are expressed in terms of mean radiation absorbed doses (Gy), dose-volume histograms, Biologically Effective Doses, Normal Tissue Complication Probability and Tumour Control Probability.

Combined quality and dose-volume histograms for assessing the predictive value of 99mTc-MAA SPECT/CT simulation for personalizing radioembolization treatment in liver metastatic colorectal cancer

BACKGROUND

The relationship between the mean absorbed dose delivered to the tumour and the outcome in liver metastases from colorectal cancer patients treated with radioembolization has already been presented in several studies. The optimization of the personalized therapeutic activity to be administered is still an open challenge. In this context, how well the 99mTc-MAA SPECT/CT predicts the absorbed dose delivered by radioembolization is essential. This work aimed to analyse the differences between predictive 99mTc-MAA-SPECT/CT and post-treatment 90Y-microsphere PET/CT dosimetry at different levels. Dose heterogeneity was compared voxel-to-voxel using the quality-volume histograms, subsequently used to demonstrate how it could be used to identify potential clinical parameters that are responsible for quantitative discrepancies between predictive and post-treatment dosimetry.

RESULTS

We analysed 130 lesions delineated in twenty-six patients. Dose-volume histograms were computed from predictive and post-treatment dosimetry for all volumes: individual lesion, whole tumoural liver (TL) and non-tumoural liver (NTL). For all dose-volume histograms, the following indices were extracted: D90, D70, D50, Dmean and D20. The results showed mostly no statistical differences between predictive and post-treatment dosimetries across all volumes and for all indices. Notably, the analysis showed no difference in terms of Dmean, confirming the results from previous studies. Quality factors representing the spread of the quality-volume histogram (QVH) curve around 0 (ideal QF = 0) were determined for lesions, TL and NTL. QVHs were classified into good (QF < 0.18), acceptable (0.18 ≤ QF < 0.3) and poor (QF ≥ 0.3) correspondence. For lesions and TL, dose- and quality-volume histograms are mostly concordant: 69% of lesions had a QF within good/acceptable categories (40% good) and 65% of TL had a QF within good/acceptable categories (23% good). For NTL, the results showed mixed results with 48% QF within the poor concordance category. Finally, it was demonstrated how QVH analysis could be used to define the parameters that predict the significant differences between predictive and post-treatment dose distributions.

CONCLUSION

It was shown that the use of the QVH is feasible in assessing the predictive value of 99mTc-MAA SPECT/CT dosimetry and in estimating the absorbed dose delivered to liver metastases from colorectal cancer via 90Y-microspheres. QVH analyses could be used in combination with DVH to enhance the predictive value of 99mTc-MAA SPECT/CT dosimetry and to assist personalized activity prescription.

Selective internal radiation therapy of hepatic tumors: Morphologic and functional imaging for voxel-based computer-aided dosimetry

Introduction:

Selective Internal Radiation Therapy (SIRT) is used for the treatment of hepatic tumors. The aim of this retrospective study was to compare two dosimetric approaches based on ^99mTc-MAA SPECT/CT and ⁹⁰Y PET/CT, using Simplicit⁹⁰Y^™versus the supplier suggested method of activity calculation.

Material and methods:

A total of 19 patients underwent 21 SIRT after baseline angiography and 99mTc-MAA SPECT/CT, followed by 90Y PET/CT. Overlap between 99mTc-MAA and 90Y-microspheres was quantified with different thresholds isocontours. The perfused volume and tumor absorbed dose were estimated using Simplicit90Y^™ based on SPECT/CT and PET/CT, then compared with the supplier suggested method. These data were related to overall survival to evaluate their prognostic impact.

Results:

The overlap between PET/CT and SPECT/CT was dependent on thresholds, decreasing with an increasing threshold. The overlap between the 99mTc-MAA and 90Y-microspheres biodistributions versus the tumor distribution on morphological imaging was suboptimal, in particular for small tumor volume. The tumor absorbed dose estimated after 90Y PET/CT was not different from tumor absorbed dose estimated after SPECT/CT. The Perfused lobe absorbed dose was significantly lower while the volume of the perfused lobe was significantly higher when estimated by Simplicit90Y^™ compared to the supplier suggested conventional approach. A statistical parameter based on overlap between tumor and 90Y-microspheres distribution as well as tumoral dosimetry was significantly related to the overall survival.

Conclusion:

Post-treatment imaging remains paramount to estimate the irradiation dosimetry, due to an imperfect overlap. The perfused volume could be estimated from functional imaging, given its impact on dosimetry. Finally, survival seems related to tumoral overlap and dosimetry.

Monte Carlo 90Y PET/CT dosimetry of unexpected focal radiation-induced lung damage after hepatic radioembolisation

Transarterial radioembolization (TARE) with ⁹⁰Y-loaded microspheres is an established therapeutic option for inoperable hepatic tumors. Increasing knowledge regarding TARE hepatic dose-response and dose-toxicity correlation is available but few studies have investigated dose-toxicity correlation in extra-hepatic tissues. We investigated absorbed dose levels for the appearance of focal lung damage in a case of off-target deposition of ⁹⁰Y microspheres and compared them with the corresponding thresholds recommended to avoiding radiation induced lung injury following TARE. A 64-year-old male patient received 1.6 GBq of ⁹⁰Y-labelled glass microspheres for an inoperable left lobe hepatocellular carcinoma. A focal off-target accumulation of radiolabeled microspheres was detected in the left lung upper lobe at the post-treatment ⁹⁰Y-PET/CT, corresponding to a radiation-induced inflammatory lung lesion at the 3-months ¹⁸F-FDG PET/CT follow-up. ⁹⁰Y-PET/CT data were used as input for Monte-Carlo based absorbed dose estimations. Dose-volume-histograms were computed to characterize the heterogeneity of absorbed dose distribution. The dose level associated with the appearance of lung tissue damage was estimated as the median absorbed dose measured at the edge of the inflammatory nodule. To account for respiratory movements and possible inaccuracy of image co-registration, three different methods were evaluated to define the irradiated off-target volume. Monte Carlo-derived absorbed dose distribution showed a highly heterogeneous absorbed dose pattern at the site of incidental microsphere deposition (volume = 2.13 ml) with a maximum dose of 630 Gy. Absorbed dose levels ranging from 119 Gy to 133 Gy, were estimated at the edge of the inflammatory nodule, depending on the procedure used to define the target volume. This report describes an original Monte Carlo based patient-specific dosimetry methodology for the study of the radiation-induced damage in a focal lung lesion after TARE. In our patient, radiation-induced focal lung damage occurred at significantly higher absorbed doses than those considered for single administration or cumulative lung dose delivered during TARE.

3D image-based dosimetry for Yttrium-90 radioembolization of hepatocellular carcinoma: Impact of imaging method on absorbed dose estimates

BACKGROUND

To improve therapy outcome of Yttrium-90 selective internal radiation therapy (⁹⁰Y SIRT), patient-specific post-therapeutic dosimetry is required. For this purpose, various dosimetric approaches based on different available imaging data have been reported. The aim of this work was to compare post-therapeutic 3D absorbed dose images using Technetium-99m (^99mTc) MAA SPECT/CT, Yttrium-90 (⁹⁰Y) bremsstrahlung (BRS) SPECT/CT, and ⁹⁰Y PET/CT.

METHODS

Ten SIRTs of nine patients with unresectable hepatocellular carcinoma (HCC) were investigated. The ^99mTc SPECT/CT data, obtained from ^99mTc-MAA-based treatment simulation prior to ⁹⁰Y SIRT, were scaled with the administered ⁹⁰Y therapy activity. 3D absorbed dose images were generated by dose kernel convolution with scaled ^99mTc/⁹⁰Y SPECT/CT, ⁹⁰Y BRS SPECT/CT, and ⁹⁰Y PET/CT data of each patient. Absorbed dose estimates in tumor and healthy liver tissue obtained using the two SPECT/CT methods were compared against ⁹⁰Y PET/CT.

RESULTS

The percentage deviation of tumor absorbed dose estimates from ⁹⁰Y PET/CT values was on average -2 ± 18% for scaled ^99mTc/⁹⁰Y SPECT/CT, whereas estimates from ⁹⁰Y BRS SPECT/CT differed on average by -50 ± 13%. For healthy liver absorbed dose estimates, all three imaging methods revealed comparable values.

CONCLUSION

The quantification capabilities of the imaging data influence ⁹⁰Y SIRT tumor dosimetry, while healthy liver absorbed dose values were comparable for all investigated imaging data. When no ⁹⁰Y PET/CT image data are available, the proposed scaled ^99mTc/⁹⁰Y SPECT/CT dosimetry method was found to be more appropriate for HCC tumor dosimetry than ⁹⁰Y BRS SPECT/CT based dosimetry.

The Impact of Radiobiologically Informed Dose Prescription on the Clinical Benefit of 90Y SIRT in Colorectal Cancer Patients

The purpose of this study was to establish the dose-response relationship of selective internal radiation therapy (SIRT) in patients with metastatic colorectal cancer (mCRC), when informed by radiobiological sensitivity parameters derived from mCRC cell lines exposed to 90Y. Methods: Twenty-three mCRC patients with liver metastases refractory to chemotherapy were included. 90Y bremsstrahlung SPECT images were transformed into dose maps assuming the local dose deposition method. Baseline and follow-up CT scans were segmented to derive liver and tumor volumes. Mean, median, and D70 (minimum dose to 70% of tumor volume) values determined from dose maps were correlated with change in tumor volume and volumetric RECIST response using linear and logistic regression, respectively. Radiosensitivity parameters determined by clonogenic assays of mCRC cell lines HT-29 and DLD-1 after exposure to 90Y or external beam radiotherapy (EBRT; 6 MV photons) were used in biologically effective dose (BED) calculations. Results: Mean administered radioactivity was 1,469 ± 428 MBq (range, 847-2,185 MBq), achieving a mean absorbed radiation dose to tumor of 35.5 ± 9.4 Gy and mean normal liver dose of 26.4 ± 6.8 Gy. A 1.0 Gy increase in mean, median, and D70 absorbed dose was associated with a reduction in tumor volume of 1.8%, 1.8%, and 1.5%, respectively, and an increased probability of a volumetric RECIST response (odds ratio, 1.09, 1.09, and 1.10, respectively). Threshold mean, median and D70 doses for response were 48.3, 48.8, and 41.8 Gy, respectively. EBRT-equivalent BEDs for 90Y are up to 50% smaller than those calculated by applying protraction-corrected radiobiological parameters derived from EBRT alone. Conclusion: Dosimetric studies have assumed equivalence between 90Y SIRT and EBRT, leading to inflation of BED for SIRT and possible undertreatment. Radiobiological parameters for 90Y were applied to a BED model, providing a calculation method that has the potential to improve assessment of tumor control.

Comparison of posttherapy 90Y positron emission tomography/computed tomography dosimetry methods in liver therapy with 90Y microspheres

The aim of our study was to compare dosimetry methods for yttrium-90 (⁹⁰Y) positron emission tomography/computed tomography (PET/CT). Twenty-five patients were taken to a PET/CT suite following therapy with ⁹⁰Y microspheres. The low mA, nondiagnostic CT images were used for attenuation correction and localization of the ⁹⁰Y microspheres. The acquisition time was 15 min, the reconstruction matrix size was 200 mm × 200 mm × 75 mm, and voxel size was 4.07 mm × 4.07 mm × 3.00 mm. Two software packages, MIM 6.8 and Planet Dose, were utilized to calculate ⁹⁰Y dosimetry. Three methods were used for voxel-based dosimetry calculations: the local deposition method (LDM), LDM with scaling (LDMwS) for known injected activity, and a dose point kernel (DPK) method using the MIRD kernel. Only the DPK approach was applied to the Planet Dose software. LDM and LDMwS were only applied to the MIM software. The average total liver dosimetry values (mean ± standard deviation) were 60.93 ± 28.62 Gy, 53.59 ± 23.47 Gy, 55.33 ± 24.80 Gy, and 54.25 ± 23.70 Gy for LDMwS, LDM, DPK with MIM, and DPK with Planet Dose (DOSI), respectively. In most cases, the LDMwS method produced slightly higher dosimetry values than the other methods. The MIM and Planet Dose DPK dosimetry values (i.e., DPK vs. DOSI) were highly comparable. Bland–Altman analysis calculated a mean difference of 1.1 ± 2.2 Gy. The repeatability coefficient was 4.4 (7.9% of the mean). The MIM and Planet Dose DPK dosimetry values were practically interchangeable. ⁹⁰Y dosimetry values obtained by all methods were similar, but LDMwS tended to produce slightly higher values.

Dose-Effect Relationships of 166Ho Radioembolization in Colorectal Cancer

Radioembolization is a treatment option for colorectal cancer (CRC) patients with inoperable, chemorefractory hepatic metastases. Personalized treatment requires established dose thresholds. Hence, the aim of this study was to explore the relationship between dose and effect (i.e., response and toxicity) in CRC patients treated with ¹⁶⁶Ho radioembolization. Methods: CRC patients treated in the HEPAR II and SIM studies were analyzed. Absorbed doses were estimated using the activity distribution on posttreatment ¹⁶⁶Ho SPECT/CT. Metabolic response was assessed using the change in total-lesion glycolysis on ¹⁸F-FDG PET/CT between baseline and 3-mo follow-up. Toxicity between treatment and 3 mo was evaluated according to the Common Terminology Criteria for Adverse Events (CTCAE), version 5, and its relationship with parenchyma-absorbed dose was assessed using linear models. The relationship between tumor-absorbed dose and patient- and tumor-level response was analyzed using linear mixed models. Using a threshold of 100% sensitivity for response, the threshold for a minimal mean tumor-absorbed dose was determined and its impact on survival was assessed. Results: Forty patients were included. The median parenchyma-absorbed dose was 37 Gy (range, 12-55 Gy). New CTCAE grade 3 or higher clinical and laboratory toxicity was present in 8 and 7 patients, respectively. For any clinical toxicity (highest grade per patient), the mean difference in parenchymal dose (Gy) per step increase in CTCAE grade category was 5.75 (95% CI, 1.18-10.32). On a patient level, metabolic response was as follows: complete response, n = 1; partial response, n = 11; stable disease, n = 17; and progressive disease, n = 8. The mean tumor-absorbed dose was 84% higher in patients with complete or partial response than in patients with progressive disease (95% CI, 20%-180%). Survival for patients with a mean tumor-absorbed dose of more than 90 Gy was significantly better than for patients with a mean tumor-absorbed dose of less than 90 Gy (hazard ratio, 0.16; 95% CI, 0.06-0.511). Conclusion: A significant dose-response relationship in CRC patients treated with ¹⁶⁶Ho radioembolization was established, and a positive association between toxicity and parenchymal dose was found. For future patients, it is advocated to use a ¹⁶⁶Ho scout dose to select patients and yo personalize the administered activity, targeting a mean tumor-absorbed dose of more than 90 Gy and a parenchymal dose of less than 55 Gy.

Additional Local Therapy for Liver Metastases in Patients with Metastatic Castration-Resistant Prostate Cancer Receiving Systemic PSMA-Targeted Therapy

The aim of this study was to evaluate the efficacy of ¹⁷⁷Lu-prostate-specific membrane antigen (PSMA)-617 (¹⁷⁷Lu-PSMA) and selective internal radiation therapy (SIRT) for the treatment of liver metastases of castration-resistant prostate cancer. Methods: Safety and survival of patients with metastatic castration-resistant prostate cancer and liver metastases assigned to ¹⁷⁷Lu-PSMA alone (n = 31) or in combination with SIRT (n = 5) were retrospectively analyzed. Additionally, a subgroup (n = 10) was analyzed using morphologic and molecular response criteria. Results: Median estimated survival was 5.7 mo for ¹⁷⁷Lu-PSMA alone and 8.4 mo for combined sequential ¹⁷⁷Lu-PSMA and SIRT. ¹⁷⁷Lu-PSMA achieved discordant therapy responses with both regressive and progressive liver metastases in the same patient (best vs. worst responding metastases per patient: -35% vs. +63% diameter change; P < 0.05). SIRT was superior to ¹⁷⁷Lu-PSMA for the treatment of liver metastases (0% vs. 56% progression). Conclusion: The combination of ¹⁷⁷Lu-PSMA and SIRT is efficient and feasible for the treatment of advanced prostate cancer. ¹⁷⁷Lu-PSMA alone seems to have limited response rates in the treatment of liver metastases.

Comparative dosimetry between 99mTc-MAA SPECT/CT and 90Y PET/CT in primary and metastatic liver tumors

INTRODUCTION

The aim of this study is to determine whether ^99mTc-MAA SPECT/CT-based dosimetry could predict the actual absorbed dose in hepatocellular carcinoma (HCC) or liver metastases, treated by glass or resin microspheres.

MATERIAL AND METHODS

Fifty-seven patients who underwent selective internal radiation therapy (SIRT) were retrospectively included in the study, for a total of 59 treatments. Nineteen HCC were treated by resin microspheres (HCC-SIR), 20 HCC with glass microspheres (HCC-Thera), and 20 liver metastases with resin microspheres (Metastases-SIR). The mean absorbed doses in tumoral liver (Dm) and non-tumoral liver (DmNTL) were determined on the ^99mTc-MAA SPECT/CT and the ⁹⁰Y PET/CT, and compared with each other.

RESULTS

DmNTL was < 50 Gy in the 3 groups, with a strong correlation in all population, albeit slightly lower in Metastases-SIR than HCC-SIR and HCC-Thera (CCC 0.8, 0.94 and 0.96, respectively). In tumoral liver, Dm was higher in HCC than metastases (159 ± 117 Gy versus 63 ± 31 Gy). ^99mTc-MAA SPECT/CT proved to be a better indicator of Dm in HCC compared with metastases, with similar ^99mTc-MAA-⁹⁰Y concordance in resin and glass microspheres (CCC HCC-SIR 0.82, CCC HCC-Thera 0.82, and CCC Metastases-SIR 0.52).

CONCLUSION

^99mTc-MAA SPECT/CT is a reasonably reliable tool for predicting the dose to the non-tumoral liver in both HCC and metastases, regardless of the type of microspheres. It is also fairly reliable for predicting the tumor dose in HCC, again regardless of the type of spheres, although individual variations are observed.

Personalised radioembolization improves outcomes in refractory intra-hepatic cholangiocarcinoma: a multicenter study

PURPOSE

Reported outcomes of patients with intra-hepatic cholangiocarcinoma (IH-CCA) treated with radioembolization are highly variable, which indicates differences in included patients' characteristics and/or procedure-related variables. This study aimed to identify patient- and treatment-related variables predictive for radioembolization outcome.

METHODS

This retrospective multicenter study enrolled 58 patients with unresectable and chemorefractory IH-CCA treated with resin ⁹⁰Y-microspheres. Clinicopathologic data were collected from patient records. Metabolic parameters of liver tumor(s) and presence of lymph node metastasis were measured on baseline ¹⁸F-FDG-PET/CT. ^99mTc-MAA tumor to liver uptake ratio (TLR_MAA) was computed for each lesion on the SPECT-CT. Activity prescription using body-surface-area (BSA) or more personalized partition-model was recorded. The study endpoint was overall survival (OS) starting from date of radioembolization. Statistical analysis was performed by the log-rank test and multivariate Cox's proportional hazards model.

RESULTS

Median OS (mOS) post-radioembolization of the entire cohort was 10.3 months. Variables associated with significant differences in terms of OS were serum albumin (hazard ratio (HR) = 2.78, 95%CI:1.29-5.98, p = 0.002), total bilirubin (HR = 2.17, 95%CI:1.14-4.12, p = 0.009), aspartate aminotransferase (HR = 2.96, 95%CI:1.50-5.84, p < 0.001), alanine aminotransferase (HR = 2.02, 95%CI:1.05-3.90, p = 0.01) and γ-GT (HR = 2.61, 95%CI:1.31-5.22, p < 0.001). The presence of lymph node metastasis as well as a TLR_MAA < 1.9 were associated with shorter mOS: HR = 2.35, 95%CI:1.08-5.11, p = 0.008 and HR = 2.92, 95%CI:1.01-8.44, p = 0.009, respectively. Finally, mOS was significantly shorter in patients treated according to the BSA method compared to the partition-model: mOS of 5.5 vs 14.9 months (HR = 2.52, 95%CI:1.23-5.16, p < 0.001). Multivariate analysis indicated that the only variable that increased outcome prediction above the clinical variables was the activity prescription method with HR of 2.26 (95%CI:1.09-4.70, p = 0.03). The average mean radiation dose to tumors was significantly higher with the partition-model (86Gy) versus BSA (38Gy).

CONCLUSION

Radioembolization efficacy in patients with unresectable recurrent and/or chemorefractory IH-CCA strongly depends on the tumor radiation dose. Personalized activity prescription should be performed.

Regorafenib Prior to Selective Internal Radiation Therapy Using 90Y-Resin Microspheres for Refractory Metastatic Colorectal Cancer Liver Metastases: Analysis of Safety, Dosimetry, and Molecular Markers

Background: This Phase II, open-label, study examined the safety of regorafenib followed by selective internal radiation therapy (SIRT) with regorafenib re-initiation in the treatment of metastatic colorectal cancer (mCRC) patients with liver metastases who are not surgical candidates.

Methods: Patients received 160 mg regorafenib daily on a 21-day course followed by a 1 week washout prior to SIRT. Liver function was evaluated at 2 and 4 weeks after SIRT, and regorafenib re-initiated if liver function was normal. Patients were evaluated for safety, and restaged at weeks 6 and 12 following SIRT. In addition, protein and cytokine assays of blood were performed to identify candidate molecular biomarkers associated with outcomes. Individual patient voxel-based dosimetry assessment was performed post-SIRT.

Results: Twenty-Five patients were enrolled and received a median 11 weeks regorafenib. Three patients received regorafenib, but not SIRT due to disease progression. The remaining 22 patients received SIRT with a median activity delivered to the liver of 38 mCi, mean normal liver dose of 14.98 Gy and tumor mean dose of 29.0 Gy with a tumor to normal ratio mean of 2.42. There were four treatment-related serious AEs and no treatment-related deaths. Median progression-free survival was 3.7 months and the median overall survival was 12.1 months. The relative densities of several biomolecules changed significantly during the course of treatment, most notably post-treatment increases in levels of sex-hormone binding globulin (SHBG) and decreased levels of the cytokine MIG (CXL9). Decreases in von Willebrand factor (VWF), the ankyrin repeat domain (ANKRD26), and MIG were associated with improved survival times. Post-treatment increases in alpha-2-macroglobulin (A2M) and the cytokine intercellular adhesion molecule (ICAM-1) were associated with reduced overall survival time, while increases in Eotaxin (CCL14) predicted longer overall survival times.

Conclusions: The treatment of mCRC patients with liver metastases using regorafenib followed by SIRT was tolerable in this patient population. Further efficacy analysis of this treatment schema and analysis of potential molecular biomarkers using larger sample sizes is merited.

Update on transarterial approaches to locoregional treatment in hepatocellular carcinoma

PURPOSE OF REVIEW

This review explores current knowledge and recent data about vascular-centered locoregional treatments and proposes alternate algorithms.

RECENT FINDINGS

Hepatocellular carcinoma represents the sixth most common neoplasm worldwide. Currently, the Barcelona Clinic Liver Cancer (BCLC) staging is the most commonly used in Europe for treatment allocation. According to this classification, European Society for Medical Oncology (ESMO) guidelines currently recommend transarterial chemoembolization for intermediate stage HCC and systemic treatments, such as, sorafenib in more advanced stages. However, strong evidences are still lacking to conclude to the superiority of one technique over another, as the optimal treatment choice remains challenging and should take into consideration more clinical, biological and imaging findings than reported in the BCLC staging system, such as patient age or clinical status, tumor characteristics (including distribution and heterogeneity), tumor vascularization and concomitant portal hypertension or biliary anomalies.

SUMMARY

Many controversies remain, in particular, the relative place of bland embolization versus chemoembolization, the clinical benefit of drug-eluting bead chemoembolization (DEB-TACE) over conventional chemoembolization (cTACE), as well as the real place of radioembolization in general setting as well as innovative applications, such as radiation segmentectomy and radiation lobectomy.