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Objective: To investigate clinical and laboratory toxicity in patients with unresectable liver metastases, treated with yttrium-90 radioembolization ((90)Y-RE)., Methods: Patients with liver metastases treated with (90)Y-RE, between February 1(st) 2009 and March 31(st) 2012, were included in this study. Clinical toxicity assessment was based on the reporting in patient's charts. Laboratory investigations at baseline and during a four-month follow-up were used to assess laboratory toxicity according to the Common Terminology Criteria for Adverse Events version 4.02. The occurrence of grade 3-4 laboratory toxicity was stratified according to treatment strategy (whole liver treatment in one session versus sequential sessions). Response assessment was performed at the level of target lesions, whole liver and overall response in accordance with RECIST 1.1 at 3- and 6 months post-treatment. Median time to progression (TTP) and overall survival were calculated by Kaplan-Meier analysis., Results: A total of 59 patients, with liver metastases from colorectal cancer (n = 30), neuroendocrine tumors (NET) (n = 6) and other primary tumors (n = 23) were included. Clinical toxicity after (90)Y-RE treatment was confined to grade 1-2 events, predominantly post-embolization symptoms. No grade 3-4 clinical toxicity was observed, whereas laboratory toxicity grade 3-4 was observed in 38% of patients. Whole liver treatment in one session was not associated with increased laboratory toxicity. Three-months disease control rates for target lesions, whole liver and overall response were 35%, 21% and 19% respectively. Median TTP was 6.2 months for target lesions, 3.3 months for the whole liver and 3.0 months for overall response. Median overall survival was 8.9 months., Conclusion: The risk of severe complications or grade 3-4 clinical toxicity in patients with liver metastases of various primary tumors undergoing (90)Y-RE is low. In contrast, laboratory toxicity grade 3-4 can be expected to occur in more than one-third of patients without any clinical signs of radiation induced liver disease.

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 ((166)HoAcAcMS). 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: (166)HoAcAcMS 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: (166)HoAcAcMS were successfully administered to tumor bearing mice. A striking near-complete tumor-control was observed in (166)HoAcAcMS treated mice (0.10±0.01 cm(3) vs. 4.15±0.3 cm(3) 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 (166)HoAcAcMS in the kidney., Conclusions: Intratumorally administered (166)HoAcAcMS 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.

Background: Scintillation camera imaging is used for treatment planning and post-treatment dosimetry in liver radioembolization (RE). In yttrium-90 (90Y) RE, scintigraphic images of technetium-99m (99mTc) are used for treatment planning, while 90Y Bremsstrahlung images are used for post-treatment dosimetry. In holmium-166 (166Ho) RE, scintigraphic images of 166Ho can be used for both treatment planning and post-treatment dosimetry. The aim of this study is to quantitatively evaluate and compare the imaging characteristics of these three isotopes, in order that imaging protocols can be optimized and RE studies with varying isotopes can be compared., Methodology/principal Findings: Phantom experiments were performed in line with NEMA guidelines to assess the spatial resolution, sensitivity, count rate linearity, and contrast recovery of 99mTc, 90Y and 166Ho. In addition, Monte Carlo simulations were performed to obtain detailed information about the history of detected photons. The results showed that the use of a broad energy window and the high-energy collimator gave optimal combination of sensitivity, spatial resolution, and primary photon fraction for 90Y Bremsstrahlung imaging, although differences with the medium-energy collimator were small. For 166Ho, the high-energy collimator also slightly outperformed the medium-energy collimator. In comparison with 99mTc, the image quality of both 90Y and 166Ho is degraded by a lower spatial resolution, a lower sensitivity, and larger scatter and collimator penetration fractions., Conclusions/significance: The quantitative evaluation of the scintillation camera characteristics presented in this study helps to optimize acquisition parameters and supports future analysis of clinical comparisons between RE studies.