In vivo tumour imaging employing regional delivery of novel gallium radiolabelled polymer composites.

BACKGROUND: Understanding the regional vascular delivery of particles to tumour sites is a prerequisite for developing new diagnostic and therapeutic composites for treatment of oncology patients. We describe a novel imageable 67Ga-radiolabelled polymer composite that is biocompatible in an animal tumour model and can be used for preclinical imaging investigations of the transit of different sized particles through arterial networks of normal and tumour-bearing organs. RESULTS: Radiolabelling of polymer microspheres with 67Ga was achieved using a simple mix and wash method, with tannic acid as an immobilising agent. Final in vitro binding yields after autoclaving averaged 94.7%. In vivo stability of the composite was demonstrated in New Zealand white rabbits by intravenous administration, and intrahepatic artery instillations were made in normal and VX2 tumour implanted rabbit livers. Stability of radiolabel was sufficient for rabbit lung and liver imaging over at least 3 hours and 1 hour respectively, with lung retention of radiolabel over 91%, and retention in both normal and VX2 implanted livers of over 95%. SPECT-CT imaging of anaesthetised animals and planar imaging of excised livers showed visible accumulation of radiolabel in tumours. Importantly, microsphere administration and complete liver dispersal was more easily achieved with 8 µm diameter MS than with 30 µm MS, and the smaller microspheres provided more distinct and localised tumour imaging. CONCLUSION: This method of producing 67Ga-radiolabelled polymer microspheres is suitable for SPECT-CT imaging of the regional vascular delivery of microspheres to tumour sites in animal models. Sharper distinction of model tumours from normal liver was obtained with smaller MS, and tumour resolution may be further improved by the use of 68Ga instead of 67Ga, to enable PET imaging.

99mTc-radiolabeled composites enabling in vivo imaging of arterial dispersal and retention of microspheres in the vascular network of rabbit lungs, liver, and liver tumors.

PURPOSE: Selective internal radiation therapy (SIRT) is an effective treatment option for liver tumors, using Y-90-loaded polymer microspheres that are delivered via catheterization of the hepatic artery. Since Y-90 is a beta emitter and not conveniently imaged by standard clinical instrumentation, dosimetry is currently evaluated in each patient using a surrogate particle, 99mTechnetium-labeled macroaggregated albumin (99mTc-MAA). We report a new composite consisting of 99mTc-labeled nanoparticles attached to the same polymer microspheres as used for SIRT, which can be imaged with standard SPECT. METHODS: Carbon nanoparticles with an encapsulated core of 99mTc were coated with the polycation protamine sulfate to provide electrostatic attachment to anionic polystyrene sulfonate microspheres of different sizes (30, 12, and 8 µm). The in vivo stability of these composites was determined via intravenous injection and entrapment in the capillary network of normal rabbit lungs for up to 3 hours. Furthermore, we evaluated their biodistribution in normal rabbit livers, and livers implanted with VX2 tumors, following intrahepatic artery instillation. RESULTS: We report distribution tests for three different sizes of radiolabeled microspheres and compare the results with those obtained using 99mTc-MAA. Lung retention of the radiolabeled microspheres ranged from 72.8% to 92.9%, with the smaller diameter microspheres showing the lowest retention. Liver retention of the microspheres was higher, with retention in normal livers ranging from 99.2% to 99.8%, and in livers with VX2 tumors from 98.2% to 99.2%. The radiolabeled microspheres clearly demonstrated preferential uptake at tumor sites due to the increased arterial perfusion produced by angiogenesis. CONCLUSION: We describe a novel use of radiolabeled carbon nanoparticles to generate an imageable microsphere that is stable in vivo under the shear stress conditions of arterial networks. Following intra-arterial instillation in the normal rabbit liver, they distribute in a distinct segmented pattern, with the smaller microspheres extending throughout the organ in finer detail, while still being well retained within the liver. Furthermore, in livers hosting an implanted VX2 tumor, they reveal the increased arterial perfusion of tumor tissue resulting from angiogenesis. These novel composites may have potential as a more representative mimic of the vascular distribution of therapeutic microspheres in patients undergoing SIRT.

Phase II trial of selective internal radiation therapy and systemic chemotherapy for liver-predominant metastases from pancreatic adenocarcinoma.

BACKGROUND: This prospective, open-label phase II study assessed the impact of liver-directed therapy with selective internal radiation therapy (SIRT) and systemic chemotherapy on progression-free survival (PFS) in liver-dominant metastatic pancreatic adenocarcinoma. METHODS: Patients received yttrium-90-labelled ((90)Y) resin microspheres (SIR-Spheres; Sirtex Medical Limited, Sydney, Australia) as a single procedure on day 2 of the first weekly cycle of 5-fluorouracil (5FU; 600 mg/m(2)) with the option to switch to gemcitabine (1000 mg/m(2)) after 8 weeks of 5FU. Statistical analysis was conducted using Microsoft Excel (Microsoft Corporation, Redmond, Washington, USA). The primary endpoint of the study was PFS in the liver, with a median of ≥ 16 weeks defined as the threshold for clinical significance. PFS and overall survival (OS) were summarised by the Kaplan-Meier method using non-parametric estimates of the survivor function. RESULTS: Fourteen eligible patients were enrolled; ten had primary tumour in situ and eight had liver-only metastases. Patients received a median (90)Y activity of 1.1 GBq and 8 weekly doses of 5FU; seven patients received a median of two doses of gemcitabine. Disease control in the liver was 93% (two confirmed partial responses [PR], one unconfirmed PR, ten stable disease). Median reduction in cancer antigen 19-9 was 72%. Median PFS was 5.2 months in the liver, which met the primary endpoint of the study, and 4.4 months at any site. PFS was prolonged in those with a resected primary compared with patients with primary in situ (median 7.8 vs. 3.4 months; p = 0.017). Median OS was 5.5 months overall and 13.6 months in patients with a resected primary. Grade 3/4 adverse events occurred in eight (57%) patients during days 0-60. There was one sudden death and another patient who died from possible treatment-related liver failure 7.0 months after SIRT. CONCLUSIONS: SIRT and chemotherapy appears to be an effective treatment for liver metastases from pancreatic cancer, likely to be of most benefit in selected patients with a resected primary tumour and liver only disease. Significant toxicity was observed and the safety of this approach in patients with metastatic pancreatic cancer will need to be confirmed in subsequent studies. Further study is warranted with SIRT and modern chemotherapies. TRIAL REGISTRATION: ACTRN12606000015549.

The uptake of soluble and nanoparticulate imaging isotope in model liver tumours after intra-venous and intra-arterial administration.

Delivery of chemotherapeutic drugs to tumours by reformulation as nanoparticles has often been proposed as a means of facilitating increased selective uptake, exploiting the increased permeability of the tumour vasculature. However realisation of this improvement in drug delivery in cancer patients has met with limited success. We have compared tumour uptake of soluble Tc99m-pertechnetate and a colloid of nanoparticles with a Tc99m core, using both intra-venous and intra-arterial routes of administration in a rabbit liver VX2 tumour model. The radiolabelled nanoparticles were tested both in untreated and cationised form. The results from this tumour model in an internal organ show a marked advantage in intra-arterial administration over the intra-venous route, even for the soluble isotope. Tumour accumulation of nanoparticles from arterial administration was augmented by cationisation of the nanoparticle surface with histone proteins, which consistently facilitated selective accumulation within microvessels at the periphery of tumours.

Treatment of fluorouracil-refractory patients with liver metastases from colorectal cancer by using yttrium-90 resin microspheres plus concomitant systemic irinotecan chemotherapy.

PURPOSE: Liver metastases are the principal cause of death in patients with advanced colorectal cancer (CRC). Irinotecan is a chemotherapeutic agent used in the treatment of CRC and has demonstrated synergistic potential when used with radiation. Radioembolization with yttrium-90 microspheres has demonstrated increased response and survival rates when given with fluorouracil chemotherapy. This study's goal was to evaluate the maximum-tolerated dose of concomitant irinotecan and radioembolization in fluorouracil-refractory patients with CRC hepatic metastases. PATIENTS AND METHODS: Twenty-five irinotecan-naive patients who had experienced relapse after previous chemotherapy were enrolled onto three dose-escalating groups. Irinotecan was administered at 50, 75, or 100 mg/m(2) on days 1 and 8 of a 3-week cycle for the first two cycles, and full irinotecan doses (ie, 100 mg/m(2)) were administered during cycles 3 to 9. Radioembolization was administered during the first chemotherapy cycle. RESULTS: Most patients experienced acute, self-limiting abdominal pain and nausea. Mild lethargy and anorexia were common. Grades 3 to 4 events were seen in three of six patients at 50 mg/m(2) (obstructive jaundice, thrombocytopenia, diarrhea), in five of 13 patients at 75 mg/m(2) (neutropenia, leukopenia, thrombocytopenia, elevated alkaline phosphatase, abdominal pain, ascites, fatigue) and in four of six patients at 100 mg/m(2) (diarrhea, deep vein thrombosis, constipation, leukopenia). Eleven (48%) of 23 patients had a partial response, and nine patients (39%) had stable disease. The median progression-free survival was 6.0 months; the median survival was 12.2 months. CONCLUSION: Concomitant use of radioembolization plus irinotecan did not reach a maximum-tolerated dose. The recommended dose of irinotecan in this setting is 100 mg/m(2) on days 1 and 8 of a 3-week cycle.

Toxicity of low dose azathioprine and 6-mercaptopurine in rat hepatocytes. Roles of xanthine oxidase and mitochondrial injury.

BACKGROUND/AIMS: To study effects of pharmacologic concentrations of azathioprine and 6-mercaptopurine (6-MP) on rat hepatocytes. METHODS: Hepatocytes cultured on matrigel were incubated with azathioprine or 6-MP; effects of putative protective agents were studied. Viability (LDH leakage), reduced (GSH) and oxidized glutathione (GSSG), mitochondrial (mt) GSH, ATP and ultrastructural changes were determined. RESULTS: Azathioprine and 6-MP (0.5-5 micromol/l) reduced viability 5-34% at day 1 and 42-92% by day 4. Allopurinol (20 microM) (xanthine oxidase inhibitor) and 2 mM Trolox (vitamin E analog) together provided near complete protection. During culture with azathioprine, GSSG increased before cell death and there was a disproportionate reduction of mtGSH and ATP, together with ultrastructural abnormalities in mitochondria. All changes were prevented by allopurinol and trolox. Discontinuation of 1 micromol/l azathioprine restored ATP levels and arrested cell injury, while culture in glucose-enriched media augmented ATP levels and ameliorated cell death. CONCLUSIONS: Clinically relevant concentrations of azathioprine and 6-MP are toxic to rat hepatocyte cultures by a mechanism that involves oxidative stress, mitochondrial injury and ATP depletion. This can lead to irreversible de-energization and cell death by oncosis (necrosis).