Radioembolization in the Treatment of Unresectable Liver Tumors: Experience Across a Range of Primary Cancers

Usefulness of multiphasic MRI in assessing suitability for SIRT in treatment of liver malignancies

AIM

To evaluate the predictive value of multiphasic magnetic resonance imaging (MRI) in identifying liver tumor perfusion characteristics and to compare it with hepatic artery perfusion scintigraphy findings in patients considered for selective internal radiation therapy (SIRT) with yttrium-90 (Y-90).

METHODS

This study included 93 patients diagnosed with primary or secondary liver cancer between May 2021 and February 2024, comprising 47 patients (27 M/20F) deemed unsuitable for SIRT and 46 patients (26 M/20F) eligible for SIRT. The relationship between multiphasic MRI and scintigraphy findings in determining perfusion of tumors was analyzed. Predictive performance was evaluated with receiver operating characteristic (ROC) analysis, and the optimal cut-off values were determined using the Youden index.

RESULTS

The SIRT unsuitable group had a lower frequency of intratumoral arterial phase hyperenhancement(APHE) (40.43% vs. 69.57%, p = 0.042), presence of hyperintensity on T2 sequence (72.34% vs. 95.65%, p = 0.026), lower lesion intensity in the portal phase (p = 0.033), and a lower lesion-to-liver intensity ratio in the portal phase (≤ 0.97, p = 0.011). The absence of intratumoral APHE [p = 0.049, AUC (95% CI) = 0.646 (0.508-0.783)] and a lesion-to-liver intensity ratio in the portal phase with a cut-off value of ≤ 0.97 [p = 0.011, AUC (95% CI) = 0.689 (0.564-0.815)] were significant predictors of SIRT unsuitability.

CONCLUSION

Both the absence of intratumoral APHE and a lower lesion-to-liver intensity ratio in the portal phase were significant predictors of SIRT unsuitability.

Recent Innovations and Nano-Delivery of Actinium-225: A Narrative Review

The actinium-225 (²²⁵Ac) radioisotope exhibits highly attractive nuclear properties for application in radionuclide therapy. However, the ²²⁵Ac radionuclide presents multiple daughter nuclides in its decay chain, which can escape the targeted site, circulate in plasma, and cause toxicity in areas such as kidneys and renal tissues. Several ameliorative strategies have been devised to circumvent this issue, including nano-delivery. Alpha-emitting radionuclides and nanotechnology applications in nuclear medicine have culminated in major advancements that offer promising therapeutic possibilities for treating several cancers. Accordingly, the importance of nanomaterials in retaining the ²²⁵Ac daughters from recoiling into unintended organs has been established. This review expounds on the advancements of targeted radionuclide therapy (TRT) as an alternative anticancer treatment. It discusses the recent developments in the preclinical and clinical investigations on ²²⁵Ac as a prospective anticancer agent. Moreover, the rationale for using nanomaterials in improving the therapeutic efficacy of α-particles in targeted alpha therapy (TAT) with an emphasis on ²²⁵Ac is discussed. Quality control measures in the preparation of ²²⁵Ac-conjugates are also highlighted.

Developments in Combining Targeted Radionuclide Therapies and Immunotherapies for Cancer Treatment

Targeted radionuclide therapy (TRT) and immunotherapy are rapidly growing classes of cancer treatments. Basic, translational, and clinical research are now investigating therapeutic combinations of these agents. In comparison to external beam radiation therapy (EBRT), TRT has the unique advantage of treating all disease sites following intravenous injection and selective tumor uptake and retention-a particularly beneficial property in metastatic disease settings. The therapeutic value of combining radiation therapy with immune checkpoint blockade to treat metastases has been demonstrated in preclinical studies, whereas results of clinical studies have been mixed. Several clinical trials combining TRT and immune checkpoint blockade have been initiated based on preclinical studies combining these with EBRT and/or TRT. Despite the interest in translation of TRT and immunotherapy combinations, many questions remain surrounding the mechanisms of interaction and the optimal approach to clinical implementation of these combinations. This review highlights the mechanisms of interaction between anti-tumor immunity and radiation therapy and the status of basic and translational research and clinical trials investigating combinations of TRT and immunotherapies.

Effects of Respiratory Motion on Y-90 PET Dosimetry for SIRT

Respiratory motion degrades the quantification accuracy of PET imaging by blurring the radioactivity distribution. In the case of post-SIRT PET-CT verification imaging, respiratory motion can lead to inaccuracies in dosimetric measures. Using an anthropomorphic phantom filled with ⁹⁰Y at a range of clinically relevant activities, together with a respiratory motion platform performing realistic motions (10–15 mm amplitude), we assessed the impact of respiratory motion on PET-derived post-SIRT dosimetry. Two PET scanners at two sites were included in the assessment. The phantom experiments showed that device-driven quiescent period respiratory motion correction improved the accuracy of the quantification with statistically significant increases in both the mean contrast recovery (+5%, p = 0.003) and the threshold activities corresponding to the dose to 80% of the volume of interest (+6%, p < 0.001). Although quiescent period gating also reduces the number of counts and hence increases the noise in the PET image, its use is encouraged where accurate quantification of the above metrics is desired.

High quality imaging and dosimetry for yttrium-90 (90Y) liver radioembolization using a SiPM-based PET/CT scanner

PURPOSE

Transarterial radioembolization (TARE) with yttrium-90 (⁹⁰Y) microspheres is a liver-directed treatment for primary and secondary hepatic malignancies. Personalized dosimetry aims for maximum treatment effect and reduced toxicity. We aimed to compare pre-treatment voxel-based dosimetry from ^99mTc macroaggregated albumin (MAA) SPECT/CT with post-treatment ⁹⁰Y PET/CT for absorbed dose values, and to evaluate image quality of ⁹⁰Y SiPM-based PET/CT.

METHODS

Forty-two patients (28 men, 14 women, mean age: 67 ± 11 years) with advanced hepatic malignancies were prospectively enrolled. Twenty patients were treated with glass and 22 with resin microspheres. Radiation absorbed doses from planning ^99mTc-MAA SPECT/CT and post-therapy ⁹⁰Y PET/CT were assessed. ⁹⁰Y PET/CT images were acquired for 20 min and reconstructed to produce 5-, 10-, 15-, and 20-min datasets, then evaluated using the 5-point Likert scale.

RESULTS

The mean administered activity was 3.44 ± 1.5 GBq for glass and 1.62 ± 0.7 GBq for resin microspheres. The mean tumor absorbed doses calculated from ^99mTc-MAA SPECT/CT and ⁹⁰Y PET/CT were 175.69 ± 113.76 Gy and 193.58 ± 111.09 Gy (P = 0.61), respectively for glass microspheres; they were 60.18 ± 42.20 Gy and 70.98 ± 49.65 Gy (P = 0.37), respectively for resin microspheres. The mean normal liver absorbed doses from ^99mTc-MAA SPECT/CT and ⁹⁰Y PET/CT were 32.70 ± 22.25 Gy and 30.62 ± 20.09 Gy (P = 0.77), respectively for glass microspheres; they were 18.33 ± 11.08 Gy and 24.32 ± 15.58 Gy (P = 0.17), respectively for resin microspheres. Image quality of ⁹⁰Y PET/CT at 5-, 10-, 15-, and 20-min scan time showed a Likert score of 3.6 ± 0.54, 4.57 ± 0.58, 4.84 ± 0.37, and 4.9 ± 0.3, respectively.

CONCLUSIONS

^99mTc-MAA SPECT/CT demonstrated great accuracy for treatment planning dosimetry. SiPM-based PET/CT scanner showed good image quality at 10-min scan time, acquired in one bed position. A PET/CT scan time of 5 min showed acceptable image quality and suffices for dosimetry and treatment verification. This allows for inclusion of ⁹⁰Y PET/CT in busy routine clinical workflows. Studies with larger patient cohorts are needed to confirm these findings.

Predictors of Overall and Progression-Free Survival in Patients with Ocular Melanoma Metastatic to the Liver Undergoing Y90 Radioembolization

PURPOSE

To investigate predictors of overall survival (OS) and progression-free survival (PFS) in patients with ocular melanoma metastatic to the liver undergoing yttrium-90 (Y90) radioembolization, including the effect of concurrent immunotherapy.

METHODS

An IRB-approved retrospective review of 24 patients with ocular melanoma metastatic to the liver who underwent Y-90 treatment between June 2003 and January 2018 was performed. Data regarding patients' performance status at the time of Y90, intra-/extrahepatic tumor burden, and treatment response were evaluated. RECIST was used to determine objective tumor response. Kaplan-Meier analysis was used to calculate OS and PFS from the first Y90 therapy. Log-rank analysis was used to determine predictors of prolonged OS and PFS.

RESULTS

Median OS from primary diagnosis and diagnosis of liver metastases was 66 months (mo) and 26.3 mo, respectively. Median OS for those who received immunotherapy within 3 months of undergoing Y90 was prolonged at 26.0 mo versus 9.5 mo for others (p = 0.014). Median OS for patients with an ECOG performance status of 0 was prolonged at 26 mo versus 5.5 mo for others (p = 0.003). Median hepatic PFS was prolonged in patients treated with Y-90 on concurrent immunotherapy at 10.3 mo versus 2.7 mo for TARE only (p = 0.002). Patients with an ECOG performance status of 0 had prolonged PFS (p = 0.002).

CONCLUSIONS

Concurrent immunotherapy and an ECOG performance status of 0 at the time of Y90 therapy appear to be predictors of prolonged OS and PFS in patients with ocular melanoma metastatic to the liver.

The physics of radioembolization

Radioembolization is an established treatment for chemoresistant and unresectable liver cancers. Currently, treatment planning is often based on semi-empirical methods, which yield acceptable toxicity profiles and have enabled the large-scale application in a palliative setting. However, recently, five large randomized controlled trials using resin microspheres failed to demonstrate a significant improvement in either progression-free survival or overall survival in both hepatocellular carcinoma and metastatic colorectal cancer. One reason for this might be that the activity prescription methods used in these studies are suboptimal for many patients.In this review, the current dosimetric methods and their caveats are evaluated. Furthermore, the current state-of-the-art of image-guided dosimetry and advanced radiobiological modeling is reviewed from a physics' perspective. The current literature is explored for the observation of robust dose-response relationships followed by an overview of recent advancements in quantitative image reconstruction in relation to image-guided dosimetry.This review is concluded with a discussion on areas where further research is necessary in order to arrive at a personalized treatment method that provides optimal tumor control and is clinically feasible.

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

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Transarterial chemoembolisation for breast cancer with liver metastasis: A systematic review

BACKGROUND

There is limited data on the impact of transarterial chemoembolisation (TACE) on survival in patients of breast cancer with liver metastasis (BCLM).

METHODS

A systematic review was conducted to assess TACE effect on BCLM patients. A search for clinical studies published since 1/1/2000 to 1/1/2017 was performed. Survival data from all studies were extracted to evaluate the efficacy of TACE, including overall survival, disease free survival and response rate. Toxic side effects data were also extracted to assess the safety of TACE.

RESULTS

A total of 10 studies with 519 BCLM patients were identified. 78.0% patients were treated with TACE, 9.9% were treated with TACE plus systematic chemotherapy and 12.1% were treated with systematic chemotherapy alone. Pooled median overall survival of patients who received TACE ranged from 7.3 to 47.0 months, median disease free survival ranged from 2.9 to 17.0 months and response rates ranged from 7.0 to 73.5%. Pooled Grade 3 and 4 side effects (blood toxicities, liver toxicity and post-embolization syndrome) ranged from 0.0 to 17.4%.

CONCLUSIONS

TACE is one of an effective treatment for BCLM and whether a specific patient is appropriate to receive TACE depends on a multiple disciplinary team discussion.

Resin Versus Glass Microspheres for 90Y Transarterial Radioembolization: Comparing Survival in Unresectable Hepatocellular Carcinoma Using Pretreatment Partition Model Dosimetry

The aim of this study was to compare survival of patients treated for unresectable hepatocellular carcinoma (uHCC) with ⁹⁰Y transarterial radioembolization (TARE) using pretreatment partition model dosimetry (PMD). Methods: We performed a retrospective analysis of prospectively collected data on 77 patients consecutively treated (mean age ± SD, 66.4 ± 12.2 y) for uHCC (36 uninodular, 5 multinodular, 36 diffuse) with ⁹⁰Y TARE (41 resin, 36 glass) using pretreatment PMD. Study endpoints were progression-free survival (PFS) and overall survival (OS) assessed by Kaplan-Meier estimates. Several variables including Barcelona Clinic Liver Cancer (BCLC) staging system, tumor size, and serum α-fetoprotein (AFP) level were investigated using Cox proportional hazards regression. Results: The characteristics of 2 groups were comparable with regard to demographic data, comorbidities, Child-Pugh score, BCLC, serum AFP level, and ⁹⁰Y global administered activity. The median follow-up time was 7.7 mo (range, 0.4-50.1 mo). Relapse occurred in 44 patients (57%) at a median of 6 mo (range, 0.4-27.9 mo) after ⁹⁰Y TARE, and 41 patients (53%) died from tumor progression. Comparison between resin and glass microspheres revealed higher but not statistically significantly PFS and OS rates in the ⁹⁰Y resin group than the ⁹⁰Y glass group (resin PFS 6.1 mo [95% confidence interval CI, 4.7-7.4] and glass PFS 5 mo [95% CI, 0.9-9.2], P = 0.53; resin OS 7.7 mo [95% CI, 7.2-8.2] and glass OS 7 mo [95% CI 1.6-12.4], P = 0.77). No significant survival difference between both types of ⁹⁰Y microspheres was observed in any subgroups of patients with early/intermediate or advanced BCLC stages. Among the variables investigated, Cox analyses showed that only in the glass group, the BCLC staging system and the serum AFP level were associated with PFS (P = 0.04) and OS (P = 0.04). Tumor size was a prognostic factor without significant influence on PFS and OS after ⁹⁰Y TARE. Conclusion: Comparison between resin and glass microspheres revealed no significant survival difference in patients treated for uHCC with ⁹⁰Y TARE using pretreatment PMD. Further, larger prospective studies are warranted to confirm these findings.

Yttrium-90 hepatic radioembolization: clinical review and current techniques in interventional radiology and personalized dosimetry

In recent years, yttrium-90 ((90)Y) microsphere radioembolization has been establishing itself as a safe and efficacious treatment for both primary and metastatic liver cancers. This extends to both first-line therapies as well as in the salvage setting. In addition, radioembolization appears efficacious for patients with portal vein thrombosis, which is currently a contraindication for surgery, transplantation and transarterial chemoembolization. This article reviews the efficacy and expanding use of (90)Y microsphere radioembolization with an added emphasis on recent advances in personalized dosimetry and interventional radiology techniques. Directions for future research into combination therapies with radioembolization and expansion into sites other than the liver are also explored.

Radiation oncology approaches in liver malignancies

Radiation therapy plays an increasingly important role in the treatment of hepatic malignancies. There is convincing evidence of safety and efficacy employing brachytherapy (yttrium-90), three-dimensional conformal radiotherapy, intensity-modulated radiotherapy, stereotactic body radiotherapy (SBRT), and proton beam therapy (PBT) in all stages of primary and metastatic involvement in the liver. Technologic advances in tumor imaging, real-time tracking of moving targets during radiotherapy delivery, and superb radiation dose deposition control have enabled treatment of previously unapproachable lesions. Recently completed and ongoing clinical trials are refining optimal dose fractionation schedules for SBRT as monotherapy. Radioembolization as part of first-line therapy in metastatic colorectal tumors is being tested in large international trials combined with FOLFOX6 and bevacizumab, as well as in hepatocellular carcinoma with sorafenib. PBT is becoming more available as new facilities open in many countries providing particle beam therapy, which delivers unparalleled control of radiation dose close to critical structures. A major point of research is understanding how best to safely destroy tumors in the background of often fragile hepatic function from cirrhosis or heavily pretreated chemotherapy liver parenchyma. Fortunately, serious complications from radiotherapy are rare, acute toxicities are typically Common Terminology Criteria for Adverse Events v4.0 grade 1-2, with consistent response rates of 50% to 97% in the modern era.

Yttrium-90 microspheres: a review of its emerging clinical indications

BACKGROUND

Many patients with liver malignancies are not candidates for resection, and systemic therapies are often not effective. Radioembolization (RE) is an alternative treatment for this group of patients. The safety and efficacy of RE with yttrium 90 (Y90) in patients with hepatocellular carcinoma (HCC) or metastatic colon cancer to the liver have been proven in several studies. However, fewer studies have focussed on the safety and efficacy of RE with Y90 in other extrahepatic primary and secondary liver cancers. The effect on outcomes of concomitant use of Y90 with a systemic therapy is still currently under investigation.

SUMMARY

A review of the published data on the use of RE as stand-alone, concomitant or sequential with other treatment modalities in HCC and other primary and secondary liver cancer is reported here.

KEY MESSAGE

RE for the treatment of HCC and other extrahepatic, primary and secondary liver cancer has reasonable efficacy and acceptable toxicities. Definitive studies to establish the role of RE in the treatment of such malignancies are warranted.

Serious hepatic complications of selective internal radiation therapy with yttrium-90 microsphere radioembolization for unresectable liver tumors

AIM

Selective internal radiation therapy with yttrium-90 microsphere radioembolization has been used to treat unresectable liver tumors and its acute toxicity has been well described. Subacute and long-term hepatic complications related to radioembolization however may be underreported in the literature. This retrospective study describes the incidence and sequelae of serious hepatic complications in patients who underwent radioembolization for unresectable liver tumors.

METHODS

A retrospective review of clinical notes of patients who received radioembolization for unresectable liver tumors from 2001 to 2011 at two Australian institutions was performed to identify those who developed clinically significant hepatic complications. Relevant clinical data were obtained and analyzed to determine their incidence and sequelae.

RESULTS

A total of 205 patients were identified, of whom 10 (4.9%) developed serious hepatic complications with 7 (3.4%) attributable to radioembolization-induced liver disease. None had preexisting underlying liver disease or progressive hepatic metastases at the time of developing hepatic complication. The median time to the onset of hepatic complications was 3.5 months (range 1-67 months); six patients had a complete resolution eventually, including one patient who subsequently underwent hepatic metastasectomy safely. Three patients died as a result of fulminant hepatic failure.

CONCLUSION

Selective internal radiation therapy with radioembolization was associated with serious hepatic complications with an incidence of 4.9% and a mortality rate of 1.5% in 205 patients from two Australian institutions. The risk of serious hepatic toxicity therefore needs to be discussed when counseling patients regarding this potential treatment option.

Quantitative Monte Carlo-based holmium-166 SPECT reconstruction

PURPOSE

Quantitative imaging of the radionuclide distribution is of increasing interest for microsphere radioembolization (RE) of liver malignancies, to aid treatment planning and dosimetry. For this purpose, holmium-166 ((166)Ho) microspheres have been developed, which can be visualized with a gamma camera. The objective of this work is to develop and evaluate a new reconstruction method for quantitative (166)Ho SPECT, including Monte Carlo-based modeling of photon contributions from the full energy spectrum.

METHODS

A fast Monte Carlo (MC) simulator was developed for simulation of (166)Ho projection images and incorporated in a statistical reconstruction algorithm (SPECT-fMC). Photon scatter and attenuation for all photons sampled from the full (166)Ho energy spectrum were modeled during reconstruction by Monte Carlo simulations. The energy- and distance-dependent collimator-detector response was modeled using precalculated convolution kernels. Phantom experiments were performed to quantitatively evaluate image contrast, image noise, count errors, and activity recovery coefficients (ARCs) of SPECT-fMC in comparison with those of an energy window-based method for correction of down-scattered high-energy photons (SPECT-DSW) and a previously presented hybrid method that combines MC simulation of photopeak scatter with energy window-based estimation of down-scattered high-energy contributions (SPECT-ppMC+DSW). Additionally, the impact of SPECT-fMC on whole-body recovered activities (A(est)) and estimated radiation absorbed doses was evaluated using clinical SPECT data of six (166)Ho RE patients.

RESULTS

At the same noise level, SPECT-fMC images showed substantially higher contrast than SPECT-DSW and SPECT-ppMC+DSW in spheres ≥ 17 mm in diameter. The count error was reduced from 29% (SPECT-DSW) and 25% (SPECT-ppMC+DSW) to 12% (SPECT-fMC). ARCs in five spherical volumes of 1.96-106.21 ml were improved from 32%-63% (SPECT-DSW) and 50%-80% (SPECT-ppMC+DSW) to 76%-103% (SPECT-fMC). Furthermore, SPECT-fMC recovered whole-body activities were most accurate (A(est) = 1.06 × A - 5.90 MBq, R(2) = 0.97) and SPECT-fMC tumor absorbed doses were significantly higher than with SPECT-DSW (p = 0.031) and SPECT-ppMC+DSW (p = 0.031).

CONCLUSIONS

The quantitative accuracy of (166)Ho SPECT is improved by Monte Carlo-based modeling of the image degrading factors. Consequently, the proposed reconstruction method enables accurate estimation of the radiation absorbed dose in clinical practice.

(⁹⁹m)Tc-MAA overestimates the absorbed dose to the lungs in radioembolization: a quantitative evaluation in patients treated with ¹⁶⁶Ho-microspheres

PURPOSE

Radiation pneumonitis is a rare but serious complication of radioembolic therapy of liver tumours. Estimation of the mean absorbed dose to the lungs based on pretreatment diagnostic (99m)Tc-macroaggregated albumin ((99m)Tc-MAA) imaging should prevent this, with administered activities adjusted accordingly. The accuracy of (99m)Tc-MAA-based lung absorbed dose estimates was evaluated and compared to absorbed dose estimates based on pretreatment diagnostic (166)Ho-microsphere imaging and to the actual lung absorbed doses after (166)Ho radioembolization.

METHODS

This prospective clinical study included 14 patients with chemorefractory, unresectable liver metastases treated with (166)Ho radioembolization. (99m)Tc-MAA-based and (166)Ho-microsphere-based estimation of lung absorbed doses was performed on pretreatment diagnostic planar scintigraphic and SPECT/CT images. The clinical analysis was preceded by an anthropomorphic torso phantom study with simulated lung shunt fractions of 0 to 30 % to determine the accuracy of the image-based lung absorbed dose estimates after (166)Ho radioembolization.

RESULTS

In the phantom study, (166)Ho SPECT/CT-based lung absorbed dose estimates were more accurate (absolute error range 0.1 to -4.4 Gy) than (166)Ho planar scintigraphy-based lung absorbed dose estimates (absolute error range 9.5 to 12.1 Gy). Clinically, the actual median lung absorbed dose was 0.02 Gy (range 0.0 to 0.7 Gy) based on posttreatment (166)Ho-microsphere SPECT/CT imaging. Lung absorbed doses estimated on the basis of pretreatment diagnostic (166)Ho-microsphere SPECT/CT imaging (median 0.02 Gy, range 0.0 to 0.4 Gy) were significantly better predictors of the actual lung absorbed doses than doses estimated on the basis of (166)Ho-microsphere planar scintigraphy (median 10.4 Gy, range 4.0 to 17.3 Gy; p < 0.001), (99m)Tc-MAA SPECT/CT imaging (median 2.5 Gy, range 1.2 to 12.3 Gy; p < 0.001), and (99m)Tc-MAA planar scintigraphy (median 5.5 Gy, range 2.3 to 18.2 Gy; p < 0.001).

CONCLUSION

In clinical practice, lung absorbed doses are significantly overestimated by pretreatment diagnostic (99m)Tc-MAA imaging. Pretreatment diagnostic (166)Ho-microsphere SPECT/CT imaging accurately predicts lung absorbed doses after (166)Ho radioembolization.

Imaging features of fibrolamellar hepatocellular carcinoma

OBJECTIVE

Fibrolamellar hepatocellular carcinoma (HCC) is a rare primary liver tumor, which significantly differs from conventional HCC. This article reviews the molecular cytogenetics, pathology, imaging features, and management of this relatively rare tumor.

CONCLUSION

Fibrolamellar HCC predominantly occurs in young patients without underlying hepatitis or cirrhosis. Serum α-fetoproteins are not elevated in most cases, and hence imaging plays an important role in diagnosis, staging, and surveillance.

Prognostic utility of 90Y radioembolization dosimetry based on fusion 99mTc-macroaggregated albumin-99mTc-sulfur colloid SPECT

Planning hepatic (90)Y radioembolization activity requires balancing toxicity with efficacy. We developed a dual-tracer SPECT fusion imaging protocol that merges data on radioactivity distribution with physiologic liver mapping.

METHODS

Twenty-five patients with colorectal carcinoma and bilobar liver metastases received whole-liver radioembolization with resin microspheres prescribed as per convention (mean administered activity, 1.69 GBq). As part of standard treatment planning, all patients underwent SPECT imaging after intraarterial injection of 37 MBq of (99m)Tc-macroaggregated albumin ((99m)Tc-MAA) to simulate subsequent (90)Y distribution. Immediately afterward, patients received 185 MBq of labeled sulfur colloid ((99m)Tc-SC) intravenously as a biomarker for normal hepatic reticuloendothelial function and SPECT was repeated. The SPECT images were coregistered and fused. A region-based method was used to predict the (90)Y radiation absorbed dose to functional liver tissue (DFL) by calculation of (99m)Tc-MAA activity in regions with (99m)Tc-SC uptake. Similarly, the absorbed dose to tumor (DT) was predicted by calculation of (99m)Tc-MAA activity in voxels without (99m)Tc-SC uptake. Laboratory data and radiographic response were measured for 3 mo, and the survival of patients was recorded. SPECT-based DT and DFL were correlated with parameters of toxicity and efficacy.

RESULTS

Toxicity, as measured by increase in serum liver enzymes, correlated significantly with SPECT-based calculation of DFL at all time points (P < 0.05) (mean DFL, 27.9 Gy). Broad biochemical toxicity (>50% increase in all liver enzymes) occurred at a DFL of 24.5 Gy and above. In addition, in uni- and multivariate analysis, SPECT-based calculation of DT (mean DT, 44.2 Gy) correlated with radiographic response (P < 0.001), decrease in serum carcinoembryonic antigen (P < 0.05), and overall survival (P < 0.01). The cutoff value of DT for prediction of 1-y survival was 55 Gy (area under the receiver-operating-characteristic curve = 0.86; P < 0.01). Patients who received a DT of more than 55 Gy had a median survival of 32.8 mo, compared with 7.2 mo in patients who received less (P < 0.05).

CONCLUSION

Dual-tracer (99m)Tc-MAA-(99m)Tc-SC fusion SPECT offers a physiology-based imaging tool with significant prognostic power that may lead to improved personalized activity planning.

Image-guided local delivery strategies enhance therapeutic nanoparticle uptake in solid tumors

Nanoparticles (NP) have emerged as a novel class of therapeutic agents that overcome many of the limitations of current cancer chemotherapeutics. However, a major challenge to many current NP platforms is unfavorable biodistribution, and limited tumor uptake, upon systemic delivery. Delivery, therefore, remains a critical barrier to widespread clinical adoption of NP therapeutics. To overcome these limitations, we have adapted the techniques of image-guided local drug delivery to develop nanoablation and nanoembolization. Nanoablation is a tumor ablative strategy that employs image-guided placement of electrodes into tumor tissue to electroporate tumor cells, resulting in a rapid influx of NPs that is not dependent on cellular uptake machinery or stage of the cell cycle. Nanoembolization involves the image-guided delivery of NPs and embolic agents directly into the blood supply of tumors. We describe the design and testing of our innovative local delivery strategies using doxorubicin-functionalized superparamagnetic iron oxide nanoparticles (DOX-SPIOs) in cell culture, and the N1S1 hepatoma and VX2 tumor models, imaged by high resolution 7T MRI. We demonstrate that local delivery techniques result in significantly increased intratumoral DOX-SPIO uptake, with limited off-target delivery in tumor-bearing animal models. The techniques described are versatile enough to be extended to any NP platform, targeting any solid organ malignancy that can be accessed via imaging guidance.

99mTc-macroaggregated albumin poorly predicts the intrahepatic distribution of 90Y resin microspheres in hepatic radioembolization

In hepatic (90)Y radioembolization, pretreatment (99m)Tc-macroaggregated albumin ((99m)Tc-MAA) nuclear imaging is used for lung shunt analysis, evaluation of extrahepatic deposition, and sometimes for treatment planning, using a partition model. A high level of agreement between pretreatment (99m)Tc-MAA distribution and final (90)Y-microsphere distribution is assumed. The aim of this study was to investigate the value of pretreatment (99m)Tc-MAA SPECT to predict intrahepatic posttreatment (90)Y-microsphere distribution.

METHODS

Volumes of interest (VOIs) were delineated on pretreatment contrast-enhanced CT or MR images according to Couinaud liver segmentation. All VOIs were registered to the (99m)Tc-MAA SPECT and (90)Y SPECT images. The (99m)Tc-MAA SPECT and (90)Y SPECT activity counts were normalized to the total administered activity of (90)Y. For each VOI, this practice resulted in a predictive amount of (90)Y (MBq/cm(3)) based on (99m)Tc-MAA SPECT in comparison with an actual amount of (90)Y based on (90)Y SPECT. Bland-Altman analysis was used to investigate the agreement of the activity distribution between (99m)Tc-MAA SPECT and (90)Y SPECT.

RESULTS

A total of 39 procedures (225 VOIs) in 31 patients were included for analysis. The overall mean difference between pretreatment and posttreatment distribution of activity concentration for all segments was -0.022 MBq/cm(3) with 95% limits of agreement of -0.581 to 0.537 MBq/cm(3) (-28.9 to 26.7 Gy absorbed dose). A difference of >10%, >20%, and >30% of the mean activity per milliliter was found in, respectively, 153 (68%), 97 (43%), and 72 (32%) of the 225 segments. In every (99m)Tc-MAA procedure, at least 1 segment showed an under- or overestimation of >10%. The position of the catheter tip during administrations, as well as the tumor load of the liver segments, significantly influenced the disagreement.

CONCLUSION

In current clinical practice, (99m)Tc-MAA distribution does not accurately predict final (90)Y activity distribution. Awareness of the importance of catheter positioning and adherence to specific recommendations may lead to optimization of individualized treatment planning based on pretreatment imaging.

Safety of repeated yttrium-90 radioembolization

PURPOSE

Repeated radioembolization (RE) treatments carry theoretically higher risk of radiation-induced hepatic injury because of the liver's cumulative memory of previous exposure. We performed a retrospective safety analysis on patients who underwent repeated RE.

METHODS

From 2004 to 2011, a total of 247 patients were treated by RE. Eight patients (5 men, 3 women, age range 51-71 years) underwent repeated treatment of a targeted territory, all with resin microspheres (SIR-Spheres; Sirtex, Lane Cove, Australia). Adverse events were graded during a standardized follow-up. In addition, the correlation between the occurrence of RE-induced liver disease (REILD) and multiple variables was investigated in univariate and multivariate analyses in all 247 patients who received RE.

RESULTS

Two patients died shortly after the second treatment (at 84 and 107 days) with signs and symptoms of REILD. Both patients underwent whole liver treatment twice (cumulative doses 3.08 and 2.66 GBq). The other 6 patients demonstrated only minor toxicities after receiving cumulative doses ranging from 2.41 to 3.88 GBq. All patients experienced objective tumor responses. In the whole population, multifactorial analysis identified three risk factors associated with REILD: repeated RE (p = 0.036), baseline serum total bilirubin (p = 0.048), and baseline serum aspartate aminotransferase (p = 0.043). Repeated RE proved to be the only independent risk factor for REILD in multivariate analysis (odds ratio 9.6; p = 0.002). Additionally, the administered activity per target volume (in GBq/L) was found to be an independent risk factor for REILD, but only in whole liver treatments (p = 0.033).

CONCLUSION

The risk of REILD appears to be elevated for repeated RE. Objective tumor responses were observed, but establishment of safety limits will require improvement in dosimetric measurement and prediction.

Intratumoral administration of holmium-166 acetylacetonate microspheres: antitumor efficacy and feasibility of multimodality imaging in renal cancer

Purpose

The increasing incidence of small renal tumors in an aging population with comorbidities has stimulated the development of minimally invasive treatments. This study aimed to assess the efficacy and demonstrate feasibility of multimodality imaging of intratumoral administration of holmium-166 microspheres (¹⁶⁶HoAcAcMS). This new technique locally ablates renal tumors through high-energy beta particles, while the gamma rays allow for nuclear imaging and the paramagnetism of holmium allows for MRI.

Methods

¹⁶⁶HoAcAcMS were administered intratumorally in orthotopic renal tumors (Balb/C mice). Post administration CT, SPECT and MRI was performed. At several time points (2 h, 1, 2, 3, 7 and 14 days) after MS administration, tumors were measured and histologically analyzed. Holmium accumulation in organs was measured using inductively coupled plasma mass spectrometry.

Results

¹⁶⁶HoAcAcMS were successfully administered to tumor bearing mice. A striking near-complete tumor-control was observed in ¹⁶⁶HoAcAcMS treated mice (0.10±0.01 cm³ vs. 4.15±0.3 cm³ for control tumors). Focal necrosis and inflammation was present from 24 h following treatment. Renal parenchyma outside the radiated region showed no histological alterations. Post administration CT, MRI and SPECT imaging revealed clear deposits of ¹⁶⁶HoAcAcMS in the kidney.

Conclusions

Intratumorally administered ¹⁶⁶HoAcAcMS has great potential as a new local treatment of renal tumors for surgically unfit patients. In addition to strong cancer control, it provides powerful multimodality imaging opportunities.

Added value of FDG-PET imaging in the diagnostic workup for yttrium-90 radioembolisation in patients with colorectal cancer liver metastases

OBJECTIVE

Yttrium-90 radioembolisation (Y90-RE) is recommended for unresectable, chemorefractory liver-dominant disease; however, the incidence of extrahepatic disease (EHD) is high. FDG-PET may have additional value to CT in demonstrating EHD. Our aim was to evaluate the added diagnostic value of FDG-PET to abdominal CT and study the influence of FDG-PET findings on treatment decisions.

METHODS

All consecutive patients with colorectal cancer liver metastases (CRCLM) referred for Y90-RE were included. Patients who underwent both CT and FDG-PET in the diagnostic workup were selected. Imaging reports were scrutinised for documented sites of EHD, and changes of management due to FDG-PET findings were determined.

RESULTS

A total of 42 patients were included. Findings on CT and FDG-PET matched in 20 patients (no EHD, n = 15; identical EHD, n = 5). In 4 patients, lesions detected on CT were not FDG-avid, and in 18 patients, FDG-PET showed more lesions than CT (P < 0.05). In 7/42 patients (17 %) a change of management was made based on the additional FDG-PET findings, i.e. exclusion from Y90-RE treatment (n = 6) and change in treatment plan (whole liver rather than segmental treatment, n = 1).

CONCLUSIONS

In patients with CRCLM referred for Y90-RE, FDG-PET showed significantly more EHD and led to a considerable change of management.

Evaluation of hepatic tumor response to yttrium-90 radioembolization therapy using texture signatures generated from contrast-enhanced CT images

RATIONALE AND OBJECTIVES

The aim of this study was to explore the use of texture features generated from liver computed tomographic (CT) datasets as potential image-based indicators of patient response to radioembolization (RE) with yttrium-90 ((90)Y) resin microspheres, an emerging locoregional therapy for advanced-stage liver cancer.

MATERIALS AND METHODS

Overall posttherapy survival and percent change in serologic tumor marker at 3 months posttherapy represent the primary clinical outcomes in this study. Thirty advanced-stage liver cancer cases (primary and metastatic) treated with RE over a 3-year period were included. Texture signatures for tumor regions, which were delineated to reveal boundaries with normal regions, were computed from pretreatment contrast-enhanced liver CT studies and evaluated for their ability to classify patient serologic response and survival.

RESULTS

A series of systematic leave-one-out cross-validation studies using soft-margin support vector machine (SVM) classifiers showed hepatic tumor texton and local binary pattern (LBP) signatures both achieve high accuracy (96%) in discriminating subjects in terms of their serologic response. The image-based indicators were also accurate in classifying subjects by survival status (80% and 93% accuracy for texton and LBP signatures, respectively).

CONCLUSIONS

Hepatic texture signatures generated from tumor regions on pretreatment triphasic CT studies were highly accurate in differentiating among subjects in terms of serologic response and survival. These image-based computational markers show promise as potential predictive tools in candidate evaluation for locoregional therapy such as RE.