Biodistribution of rhenium-188 Lipiodol infused via the hepatic artery of rats with hepatic tumours

Transarterial Radioembolization (TARE) Agents beyond 90Y-Microspheres

Liver malignancies, either primary tumours (mainly hepatocellular carcinoma and cholangiocarcinoma) or secondary hepatic metastases, are a major cause of death, with an increasing incidence. Among them, hepatocellular carcinoma (HCC) presents with a dark prognosis because of underlying liver diseases and an often late diagnosis. A curative surgical treatment can therefore only be proposed in 20 to 30% of the patients. However, new treatment options for intermediate to advanced stages, such as internal radionuclide therapy, seem particularly attractive. Transarterial radioembolization (TARE), which consists in the use of intra-arterial injection of a radiolabelled embolising agent, has led to very promising results. TARE with 90Y-loaded microspheres is now becoming an established procedure to treat liver tumours, with two commercially available products (namely, SIR-Sphere® and TheraSphere®). However, this technology remains expensive and is thus not available everywhere. The aim of this review is to describe TARE alternative technologies currently developed and investigated in clinical trials, with special emphasis on HCC.

Mechanism of Action, Pharmacokinetics, Efficacy, and Safety of Transarterial Therapies Using Ethiodized Oil: Preclinical Review in Liver Cancer Models

PURPOSE

To systematically review mechanism of action, pharmacokinetics (PKs), efficacy, and safety of ethiodized oil-based locoregional therapy (LRT) for liver cancer in preclinical models.

MATERIALS AND METHODS

A MEDLINE search was performed from 1988 to 2016. Search terms included hepatocellular carcinoma (HCC), HCC, liver-cell carcinoma, liver, hepatic, hepatocarcinoma, transarterial or chemoembolization, TACE, animal, Lipiodol, Ethiodol, iodized oil, and/or poppy-seed oil. Inclusion criteria were: publication in a peer-reviewed journal, an accepted animal model, and PK/safety/efficacy data reported. Exclusion criteria were: inadequate PK, safety, or efficacy data; anticancer drug name/dose not available; and article not in English. Outcomes included intratumoral anticancer drug uptake, PKs, tolerance, tumor response, and survival.

RESULTS

Of 102 identified articles, 49 (49%) met the inclusion criteria. Seventeen, 35, and 2 articles used rat, rabbit, and pig models. Mechanism of action was investigated in 11 articles. Eleven articles reported drug uptake, PK, and tolerance data, showing 0.5%-9.5% of injected chemotherapy dose in tumor. Tumor-to-liver drug distribution ratios were 2-157. Toxicology data across 6 articles showed transient liver laboratory level elevations 1 day after LRT. There was no noteworthy liver or extrahepatic histologic damage. Nine articles reported tumor response, with 0%-30% viable tumor and -10% to -38% tumor growth at 7 days after LRT. Two articles reported survival, showing significantly longer survival after LRT vs untreated controls (56/60 d vs 33/28 d). Several articles described ethiodized oil mixed with radiopharmaceutical (n = 7), antiangiogenic (n = 6), gene (n = 6), nanoembolic (n = 5), immune (n = 2), or other novel (n = 1) agents.

CONCLUSIONS

Animal studies show preferential tumor uptake of anticancer agent, good hepatic/systemic tolerance, high tumor response, and enhanced survival after ethiodized oil-based LRT.

Development of 4-hexadecyl-4,7-diaza-1,10-decanedithiol (HDD) kit for the preparation of the liver cancer therapeutic agent Re-188-HDD/lipiodol

INTRODUCTION

A lipiodol solution of (188)Re-4-hexadecyl-2,2,9,9-tetramethyl-4,7-diaza-1,10-decanedithiol (HTDD) has been successfully developed for liver cancer therapy; however, its preparation requires a multi-step synthesis and it is characterized by a low labeling yield.

METHODS

We synthesized a new compound, 4-hexadecyl-4,7-diaza-1,10-decanedithioacetate (AHDD), without gem dimethyl groups to address these issues. AHDD was formulated into a kit and was labeled with (188)Re. Biodistribution study was performed using normal BALB/c mice.

RESULTS

The kit was labeled with (188)Re with a high efficiency (98.8±0.2%). After extraction with lipiodol, the overall yield of (188)Re-HDD/lipiodol was as high as 90.2±2.6%. A comparative biodistribution study of (188)Re-HTDD and (188)Re-HDD was performed in normal mice after intravenous injection. The lungs were identified as the main uptake site due to capillary-blockage. (188)Re-HDD/lipiodol showed a significantly higher lung uptake than that of (188)Re-HTDD/lipiodol (p<0.05).

CONCLUSION

The newly synthesized (188)Re-HDD/lipiodol showed improved radiolabeling yield and biodistribution results compared to (188)Re-HTDD/lipiodol, and may therefore be more suitable for liver cancer therapy.

Mixed-ligand complexes of yttrium-90 dialkyldithiocarbamates with 1,10-phenanthroline as a possible agent for therapy of hepatocellular carcinoma

Yttrium-90 is a radioelement which has found wide use in targeted radionuclide therapy because of its attractive physical and chemical properties. Radioembolisation of hepatocellular carcinoma with radiolabelled Lipiodol is a method of choice. We have synthesised a series of alkyldithiocarbamate yttrium complexes, easily extracted into Lipiodol due to their high lipophilicity. Among the prepared series, a new radioconjugate, which is stable over an extended period of time, has been prepared, and could represent a potential treatment procedure for hepatocellular carcinoma.

High performance liquid chromatography-tandem mass spectrometry method for ex vivo metabolic studies of a rhenium-labeled radiopharmaceutical for liver cancer

The radio-isotope rhenium-labeled N-[2-(triphenylmethyl)thioethyl]-3-aza-19-ethyloxycarbonyl-3-[2-(triphenylmethyl)thioethyl] octadecanoate) ligand (188Re-MN-16ET) is a novel therapeutic agent under preclinical evaluation for hepatoma. A reversed-phase high performance liquid chromatography coupled with a tandem mass spectrometric analysis method and diode array detector (DAD) involving a T type splitter was developed to characterize this pharmaceutical in rat liver tissue solution and determine its biotransformation rate. The separation was accomplished on a C18 column (chromolith silica, 4.6 mm x 100 mm) using an acetonitrile-ammonium acetate buffer gradient as the mobile phase. The detection was achieved by DAD set at 250nm and tandem mass spectrometry using electrospray ionization in the positive ion mode. Re-MN-16ET displayed a retention time of 23.2 min and a transition ion pair corresponding to m/z677 --> 631 for multiple reaction monitoring. Its biotransformation reaction in rat liver homogenate proceeded for 90 min in a 37°C water bath. The characterization was conducted using aliquots that were extracted and concentrated from the reaction mixture for various incubation times. Re-MN-16ET exhibited a biotransformation half-life (t1/2) of 8-9 min in liver tissue solution and was almost completely exhausted after 90 min. Two of its metabolites, consisting of the Re-labeled carboxylic acid derivative, predominately, and its corresponding demetallized disulfide ligand were found in the liver homogenate, providing a metabolism pathway for the radio-pharmaceutical.

188W/188Re Generator System and Its Therapeutic Applications

The188Re radioisotope represents a useful radioisotope for the preparation of radiopharmaceuticals for therapeutic applications, particularly because of its favorable nuclear properties. The nuclide decay pattern is through the emission of a principle beta particle having 2.12 MeV maximum energy, which is enough to penetrate and destroy abnormal tissues, and principle gamma rays (Eγ=155 keV), which can efficiently be used for imaging and calculations of radiation dose.188Re may be conveniently produced by188W/188Re generator systems. The challenges related to the double neutron capture reaction route to provide only modest yield of the parent188W radionuclide indeed have been one of the major issues about the use of188Re in nuclear medicine. Since the specific activity of188W used in the generator is relatively low (<185 GBq/g), the elutedRe188O4-can have a low radioactive concentration, often ineffective for radiopharmaceutical preparation. However, several efficient postelution concentration techniques have been developed, which yield clinically usefulRe188O4-solutions. This review summarizes the technologies developed for the preparation of188W/188Re generators, postelution concentration of the188Re perrhenate eluate, and a brief discussion of new chemical strategies available for the very high yield preparation of188Re radiopharmaceuticals.

Therapeutic efficacy of 188Re-MN-16ET lipiodol in an animal model of hepatocellular carcinoma

OBJECTIVE

In our recent study, we developed a new radiopharmaceutical (Re-188 MN-16ET lipiodol) with encouraging results for the treatment of liver malignancy. In this study, we further evaluated the therapeutic efficacy of this radiopharmaceutical by measuring tumor response and survival times in rats with liver tumors after intra-hepatic arterial injection of Re-188 MN-16ET lipiodol.

METHODS

Twelve male rats bearing hepatic tumors were divided into three groups. Group 1 received an intra-hepatic arterial injection of 18.5 MBq Re-188 MN-16ET lipiodol; Group 2 received lipiodol and Group 3 received normal saline. Tumor size was measured by liver sonography before injection, at 2, 4, and 8 weeks after injection. Survival time and response rate were calculated.

RESULTS

All rats showed good response and survived over 60 days in Group 1 while all rats showed poor response in Group 2 and Group 3 with only 25 % of rats in Group 2 and none (0 %) in Group 3 survived over 60 days. The p value was 0.0067 between Group 1 and Group 3; 0.04 between Group 1 and Group 2; and 0.034 between Group 2 and Group 3.

CONCLUSION

Re-188 MN-16ET lipiodol has good potential for the treatment of hepatoma.

Synthesis and application of 188Re-MN-16ET/Lipiodol in a hepatocellular carcinoma animal model

INTRODUCTION

Hepatocellular carcinoma is the most common form of primary hepatic carcinoma. A new N(2)S(2) tetradentate ligand, N-[2-(triphenylmethyl)thioethyl]-3-aza-19-ethyloxycarbonyl-3-[2-(triphenylmethyl)thioethyl]octadecanoate (H(3)MN-16ET), was introduced and labeled with (188)Re to create (188)Re-MN-16ET in the Lipiodol phase. The potential of (188)Re-MN-16ET/Lipiodol for hepatoma therapy was evaluated in a hepatocellular carcinoma animal model of Sprague-Dawley rats implanted with the N1S1 cell line.

METHODS

Synthesis of H(3)MN-16ET was described, and characterization was identified by infrared, nuclear magnetic resonance and mass spectra. We compared the effects of transchelating agents (glucoheptonate or tartaric acid) and a reducing agent (stannous chloride) on the complexing of (188)Re-perrhenate and H(3)MN-16ET. Twenty-four rats implanted with hepatoma were injected with 3.7 MBq/0.1 ml of (188)Re-MN-16ET/Lipiodol or (188)Re-MN-16ET via transcatheter arterial embolization. Biodistribution experiments and single-photon emission computed tomography imaging were performed to investigate tumor accumulation.

RESULTS

H(3)MN-16ET was proved to easily conjugate with the Re isotope and showed good solubility in Lipiodol. The radiochemical purity of (188)Re-MN-16ET/Lipiodol with 10 mg tartaric acid and stannous chloride was shown to be more than 90%. The major distribution sites of (188)Re-MN-16ET in Sprague-Dawley rats were hepatoma and the liver. However, the radioactivity at the tumor site postadministered with (188)Re-MN-16ET was quickly decreased from 9.15±0.23 (at 1 h) to 2.71%±0.18% of injected dose/g (at 48 h). The biodistribution and micro-single-photon emission computed tomography/computed tomography image data showed that (188)Re-MN-16ET/Lipiodol was selectively retained at the tumor site, with 11.55±1.44, 13.16±1.46 and 10.67%±0.95% of injected dose/g at 1, 24 and 48 h postinjection, respectively. The radioactivity in normal liver tissue was high but significantly lower than that of the tumors.

CONCLUSION

H(3)MN-16ET is a suitable tetradentate ligand for (188)Re labeling. From the animal data, we suggest that (188)Re-MN-16ET/Lipiodol has the potential to be a therapeutic radiopharmaceutical for hepatoma treatment.

ZT glue immobilizes iodinated oil in vivo

PURPOSE

ZT glue immobilizes iodinated oil to raise treatment efficiency.

MATERIALS AND METHODS

ZT glue and iodinated oil were mixed at a series of volume ratios on a level surface which be put vertically after 30 min. Five Sprague-Dawley rats (group 1) were subcutaneously injected in the groin with ZT glue and (131)I-iodinated oil (volume ratio at 1:4, 0.1 ml per rat, (131)I activity 13.6 x 37 x 10(3)Bq), at 1, 8, 12, and 27 days, a SPECT plain scan was performed to observe the (131)I distribution in the body, and to calculate the gamma counts at the site of injection. At 28 days, the rats were sacrificed and organs were collected. Iodinated oil states at the injection spot were recorded. Specimens from organs and the injection spot were used to detect gamma counts. Another five Sprague-Dawley rats (group 2) were subcutaneously injected (131)I-iodinated oil in the groin as control group. Through portal vein, five rabbits right liver lobe received (131)I-iodinated oil (1 ml, 20 x 37 x 10(3)Bq)+ZT glue (0.25 ml). gamma counts in the liver region were recorded on days 0, 1, 2, 3, 4, 5, 6, 7, 9, 12, 15, 21, 27, and 33 after surgery. Then, gamma counting and pathological examination of the liver specimen and the lung specimen were performed. All gamma counts data was processed by INDFIT1.0 software that was designed in our laboratory to establish nuclide metabolic equation.

RESULT

The mixed iodinated oil above the volume ratio of 1:12 stop at level surface local. At rat the injection site, the nuclide stagnation time of group 1 are longer than those of group 2, and the biological half-life of group 1 is four times that of group 2. Single agent analysis of variance comparing the biological half-life: F value is 81.999, p<0.001. No visible damage was seen in the rat organs. All rat organs except the liver had no statistically significant gamma counts difference. Tissue gamma counts at the site of injection at day 28 had statistically difference between the two rat groups, F value is 5.608, p=0.045. The iodinated oil metabolic patterns in rabbit liver revealed two portions, the rapid and the slow. ZT glue rabbit group had higher slow proportion than iodinated oil group. Pearson Goodness-of-Fit Chi-square test found the Chi-square value was 25.433, d.f.=6, p<0.0001. ZT glue rabbit group right liver lobe has iodinated oil and ZT glue depositing, some liver cells were degenerated and vacuolated in the cellular plasma. Fibrous tissue proliferated around hepatic portal canal regions.

CONCLUSION

ZT glue fixed iodinated oil is possible in vivo. This provides a new potentiality to delay iodinated oil metabolic in clinical liver cancer interventional treatment.

Development of acetylated HDD kit for preparation of 188Re-HDD/lipiodol

A lipiodol solution of (188)Re-4-hexadecyl-2,2,9,9-tetramethyl-4,7-diaza-1,10-decanedithiol ((188)Re-HDD/lipiodol) is in clinical study for liver cancer therapy. However, formulation of it is difficult due to highly active and unstable sulfhydryl groups. We produced new kits using diacetylated HDD (AHDD), in which sulfhydryl groups are protected. We found that AHDD kit can replace HDD kit due to an increased stability for formulation, the better radiolabeling efficiency (78%) and the equivalent biodistribution pattern in mice.

Clinical applications of 188Re-labelled radiopharmaceuticals for radionuclide therapy

188Re is a radionuclide in which there is widespread interest for therapeutic purposes because of its favourable physical characteristics. Moreover, it can be eluted from an on-site installable 188W/188Re generator, which has a useful shelf-life of several months. Most of the clinical experiences gained with 188Re concern the use of 188Re-1,1-hydroxyethylidenediphosphonate (188Re-HEDP) for bone pain palliation in patients suffering prostate cancer. The maximum tolerated activity was 3.3 GBq 188Re-HEDP and if the platelet count exceeded 200 x 10(9) l(-1), the administration of 4.4 GBq appeared safe. Evidence for repeated administrations of 188Re-HEDP rather than single injections was established. In general, pain palliation occurs in 60-92% of patients with only moderate transient toxicity, mainly related to changes in blood counts. Also in haematology, radioimmunotherapy by means of 188Re might play a role by selectively targeting the bone marrow in patients undergoing conditioning prior to haematopoetic stem cell transplantation. The feasibility of such an approach was proven using a Re-labelled monoclonal antibody directed toward the CD66-antigen. More recently, encouraging safety data on locoregional treatment of primary liver tumours using 188Re-labelled lipiodol were reported. The normal organs at greatest risk for toxicity are the normal liver and the lungs. About 50% of the patients reported mild and transient side effects, mainly consisting of low grade fever, right hypochondrial discomfort or aggravation of pre-existing liver impairment. Besides the applications in oncology 188Re-based therapies have also been pioneered for benign condition such as prevention of re-stenosis following angioplasty and for radiosynovectomy in cases of refractory arthritis.

Effect of a 188Re-SSS lipiodol/131I-lipiodol mixture, 188Re-SSS lipiodol alone or 131I-lipiodol alone on the survival of rats with hepatocellular carcinoma

BACKGROUND AND AIM

It has been shown that the use of a cocktail of isotopes of different ranges of action leads to an increase in the effectiveness of metabolic radiotherapy. The purpose of the present study was to compare with a control group the effectiveness of three different treatments in rats bearing hepatocellular carcinoma (HCC), using (1) a mixture of lipiodol labelled with both I and Re, (2) lipiodol labelled with I alone and (3) lipiodol labelled with Re alone.

MATERIAL AND METHODS

Four groups were made up, each containing 14 rats with the N1-S1 tumour cell line. Group 1 received a mixture composed of 22 MBq of Re-SSS lipiodol and 7 MBq I-lipiodol. Group 2 received 14 MBq I-lipiodol. Group 3 received 44 MBq of Re-SSS lipiodol and group 4 acted as the control. The survival of the various groups was compared by a non-parametric test of log-rank, after a follow-up of 60, 180 and 273 days.

RESULTS

Compared with the controls, the rats treated with a mixture of Re-SSS lipiodol and I-lipiodol show an increase in survival, but only from day 60 onwards (P=0.05 at day 60 and 0.13 at days 180 and 273). For the rats treated with I-lipiodol, there was a highly significant increase in survival compared with the controls at day 60, day 180 and day 273 (P=0.03, 0.04 and 0.04, respectively). There is no significant increase in survival for the rats treated with Re-SSS lipiodol, irrespective of the follow-up duration (P=0.53 at day 60, 0.48 at day 180, and 0.59 at day 273).

CONCLUSIONS

In this study, I-lipiodol is the most effective treatment in HCC-bearing rats, because this is the only method that leads to a prolonged improvement of survival. These results cannot necessarily be extrapolated to humans because of the relatively small size and unifocal nature of the lesions in this study. It appears necessary to carry out a study in humans with larger tumours in order to compare these three treatments, particularly with a view to replacing I-labelled lipiodol by Re-labelled lipiodol. However, this study clearly demonstrated that, for small tumours, as in an adjuvant setting for example, I-labelled lipiodol should be a better option than Re-labelled lipiodol.

Treatment of hepatocellular carcinoma by means of radiopharmaceuticals

Several techniques have been developed for radionuclide therapy of hepatocellular carcinoma (HCC). Medical literature databases (Pubmed, Medline) were screened for available literature and articles were critically analysed as to their scientific relevance. In a palliative setting, intra-arterial administration of 131I-Lipiodol yields responses in 17-92% of patients. According to a randomised study, 131I-Lipiodol was far better tolerated than classic chemo-embolisation. The additive value of a single 131I-Lipiodol administration following partial liver resection for HCC was evaluated and evidence is available that adjuvant radionuclide treatment reduces the recurrence rate. Data concerning the role of 131I-Lipiodol in bridging patient to liver transplantation are scarce but suggest a potential benefit in terms of reducing the drop-out rate while patients are listed for transplantation. 188Re- and 90Y-labelled conjugates are emerging and initial clinical data are promising. Treatment of HCC with 90Y-labelled microspheres is likely as efficacious as treatment with radiolabelled Lipiodol but pretreatment 99mTc-MAA scintigraphy is required in order to exclude patients with significant lung shunting. Several antibodies targeting antigens expressed on HCC have been radiolabelled, almost exclusively with 131I, and evaluated in a preclinical or clinical setting. The use of radiolabelled Lipiodol and microspheres allows for selective targeting of HCC with limited toxicity. Prospective, randomised controlled trials demonstrating that both treatment modalities may provide a survival benefit in a palliative setting are mandatory. In addition, future research should focus on the complementary role of radionuclide treatment in patients at risk for recurrent disease following partial liver resection or while awaiting liver transplantation.

188Re-labeled bisphosphonates as potential bifunctional agents for therapy in patients with bone metastases

Two new bisphosphonates have been examined for their ability to bind 188Re and deliver it selectively to bone. The bisphosphonates are prototype compounds with potential to deliver rhenium radionuclides and a second therapy modality to bone metastases. A conjugate between diethylenetriaminepentaacetic acid and bisphosphonate (DTPA/BP) and a conjugate between 5-fluorouracil and bisphosphonate (5-FU/BP) were prepared and labeled at high radiochemical purity with 188Re and biodistribution studies were carried out in normal Balb/C mice. The compounds showed rapid blood clearance and elimination from soft tissues with substantial retention of activity in the bone comparable to 188Re-hydroxyethylidine diphosphonate used as a control. At 8 h bone activity was 3.51% of injected dose for 188Re-DTPA/BP and 6.38% of injected dose for 188Re-5-FU/BP representing 69.6% and 80.6% of total body radioactivity, respectively. The two compounds show the potential for combination therapy of painful bone metastases.

A kit formulation for the preparation of 188Re-lipiodol: preclinical studies and preliminary therapeutic evaluation in patients with unresectable hepatocellular carcinoma

A lyophilized kit formulation for the efficient labelling of lipiodol with generator-produced rhenium-188 is described. The preliminary preparation of the lipophilic complex bis-(diethyldithiocarbamato)nitrido rhenium-188 (188ReN-DEDC) was carried out using a two-vial kit containing S-methyl-N-methyl-dithiocarbazate, SnCl2 and sodium oxalate in the first vial, and diethyldithiocarbamate and a carbonate buffer in the second vial. After mixing of the reaction solution with lipiodol, the complex 188ReN-DEDC was quantitatively extracted and retained by this hydrophobic substance, thus allowing the stable incorporation of the beta-emitting radionuclide. The radiochemical purity of the complex 188ReN-DEDC was 97+/-2%. The activity extracted into the lipiodol phase was 96+/-3% of the initial activity, indicating that the complex 188ReN-DEDC was almost quantitatively removed from the aqueous reaction solution. In vitro stability studies in human plasma, at 37 degrees C, demonstrated the release of less than 15% of the activity within three half-lives. The biodistribution of Re-lipiodol in non-tumour-bearing Wistar rats at 6, 24, 48 and 72 h after intraportal venous injection showed one-third of total activity in the liver at 6 h, declining to 2% retention at 72 h. Bowel uptake at 6 and 24 h declined to low levels at 48 and 72 h. Renal activity peaked at 1.7%, diminishing to 0.6% over 48 h. Rat whole body gamma imaging showed gut activity in addition to hepatic uptake at 6 and 24 h, but only liver was evident from 48 to 72 h. Kidneys were not demonstrable at any imaging time point. In nine patients, activity was localized in the tumours immediately following intrahepatic arterial injection. Computed tomography/single-photon emission computed tomography (CT/SPECT) imaging at 1 and 24 h confirmed the retention of 188Re-lipiodol in the hepatoma, with minimal gut uptake and no lung activity over 24 h. These patients were subsequently treated with activities of 2.5-5 GBq of 188Re-lipiodol fractions without adverse effects. Six patients followed for up to 2 years in the pilot study achieved stable disease and there was objective partial response in one patient. Repeated treatments were performed on two to three occasions in three patients without evident toxicity. An additional patient given 6 GBq of 188Re-lipiodol demonstrated myelosuppression, which recovered with granulocyte colony-stimulating factor (GCSF) and platelet support. It is concluded that 188Re-lipiodol, prepared using our novel kit formulation, is stable in vivo and provides safe and effective therapy of unresectable hepatocellular carcinoma when given via the hepatic artery, either alone or in combination with transarterial chemoembolization.

Preparation and biodistribution of rhenium-188 ECD/Lipiodol in rats following hepatic arterial injection

Radiolabeled Lipiodol has routinely been used in hepatoma therapy. In this article an attempt to develop a new (188)Re-ECD/Lipiodol radiopharmaceutical, in which the chelating agent ECD (ethyl cyteinate dimer), is the constituent of the known brain perfusion agent (99m)Tc-ECD, and an evaluation of its stability and biodistribution in rats with hepatic tumors is presented. First, (188)Re-ECD was prepared in a vial, followed by extraction with Lipiodol to get the final product, (188)Re-ECD/Lipiodol. The optimal labeling conditions for (188)Re-ECD were: (1) tartaric acid which is better than EDTA as a weak chelating agent; and (2) 15 mg of SnCl(2), as the reducing agent, and 5-10 mg of tartaric acid in each vial had a better labeling yield. The radiochemical purity of (188)Re-ECD/Lipiodol was more than 94%. Twenty-four male Sprague-Dawley rats with liver tumors were sacrificed at 1, 24, and 48 h (eight rats each time) after an injection of approximately 7.4 MBq of (188)Re-ECD/Lipiodol via the hepatic artery. The radioactivity in the liver tumor is significantly high following therapeutic arterial injection, and relatively low in other organs including the bone, spleen, brain, thyroid, stomach, muscle, blood, and testis throughout this study. In conclusion, the new preparation of (188)Re-ECD/Lipiodol is a candidate agent for the treatment of liver cancer.

Development of 99mTc labelled Lipiodol: biodistribution following injection into the hepatic artery of the healthy pig

BACKGROUND

We develop a method for the radiolabelling of Lipiodol with Tc, using a lipophilic complex, [99mTc-(S2CPh)(S3Ph)2], dissolved in Lipiodol (99mTc-SSS Lipiodol).

RESULTS

The labelling yield is high (96 +/- 0.8%), and the radiochemical purity satisfactory (92 +/- 2.6%). This labelling is reproducible and stable for up to 24 h in vitro. Studies carried out after injection into the hepatic artery of the healthy pig show that the biodistribution of 99mTc-SSS Lipiodol is comparable with that observed for 188Re Lipiodol.

MATERIALS AND METHODS

The 99mTc-SSS lipiodol was obtained after dissolving a chelating agent, previously labelled with 99mTc, in cold lipiodol. The radiochemical purity (RCP) of the labelling was checked immediately and at 24 h. The 99mTc-SSS lipiodol was injected into the hepatic artery of four healthy pigs for an ex-vivo biodistribution study. An autoradiographic study was performed in two cases.

CONCLUSIONS

Apart from the specific interest of a Lipiodol-bearing technetiated agent for carrying out dosimetric studies, the labelling of Lipiodol with 99mTc is a preliminary step towards the use of radiolabelling with the 188Re analogue.

188Re-SSS lipiodol: radiolabelling and biodistribution following injection into the hepatic artery of rats bearing hepatoma

BACKGROUND

Although intra-arterial radiation therapy with 131I-lipiodol is a useful therapeutic approach to the treatment of hepatocellular carcinoma, various disadvantages limit its use.

AIM

To describe the development of a method for the labelling of lipiodol with 188Re-SSS (188Re (S2CPh)(S3CPh)2 complex) and to investigate its biodistribution after injection into the hepatic artery of rats with hepatoma.

METHODS

188Re-SSS lipiodol was obtained after dissolving a chelating agent, previously labelled with 188Re, in cold lipiodol. The radiochemical purity (RCP) of labelling was checked immediately. The 188Re-SSS lipiodol was injected into the hepatic artery of nine rats with a Novikoff hepatoma. They were sacrificed 1, 24 and 48 h after injection, and used for ex vivo counting.

RESULTS

Labelling of 188Re-SSS lipiodol was achieved with a yield of 97.3+/-2.1%. The immediate RCP was 94.1+/-1.7%. Ex vivo counting confirmed a predominantly hepatic uptake, with a good tumoral retention of 188Re-SSS lipiodol, a weak pulmonary uptake and a very faint digestive uptake. The 'tumour/non-tumoral liver' ratio was high at 1, 24 and 48 h after injection (2.9+/-1.5, 4.1+/-/4.1 and 4.1+/-0.7, respectively).

CONCLUSIONS

Using the method described here, 188Re-SSS lipiodol can be obtained with a very high yield and a satisfactory RCP. The biodistribution in rats with hepatoma indicates a good tumoral retention of 188Re-SSS lipiodol associated with a predominant hepatic uptake, a weak pulmonary uptake and a very faint digestive uptake. This product should be considered for intra-arterial radiation therapy in human hepatoma.

Transcatheter Arterial Embolization with 188Rhenium-HDD–labeled Iodized Oil in Rabbit VX2 Liver Tumor

PURPOSE

To evaluate the antitumor effect of transcatheter arterial embolization (TAE) with use of rhenium 188 HDD (4-hexadecyl 2,2,9,9-tetramethyl-4,7-diaza-1,10-decanethiol)-labeled iodized oil and to compare it with that of transcatheter arterial chemoembolization (TACE) with use of an established chemotherapeutic agent and iodized oil in experimentally induced liver tumor.

MATERIALS AND METHODS

VX2 carcinoma was grown in the livers of 57 rabbits. TAE was performed with (188)Re-HDD-labeled iodized oil (Re-Lp group; n = 21), doxorubicin/iodized oil emulsion (Dx-Lp group; n = 21), and iodized oil alone (n = 15). Sequential conjugated planar imaging was performed for dosimetry of the radioisotope in the Re-Lp group (n = 15). Growth ratio and percentage of viable tumor were estimated by computed tomography and histopathologic examination. Hepatic and hematologic toxicities were evaluated by biochemical analysis.

RESULTS

On conjugated planar imaging, radioactivity was concentrated on the tumor (effective half-life, 16.2 hours), and mean radiation dose to the tumor was 147.7 Gy. The mean growth ratios 1, 2, and 3 weeks after TAE and the percentage of viable tumor in the Re-Lp group (-3.4, -7.6, -11.1, and 0.3%) and the Dx-Lp group (-3.2, -5.3, 29.0, and 2.6%) were significantly lower than the respective values in the iodized oil group (45.5, 145.4, 283.0, and 30.1%; P < .001). However, the differences between the values in the Re-Lp group and those in the Dx-Lp group were not significant (P values of .165-0.497 for growth ratios; P = .134 for percentage of viable tumor). There was similar transient hepatotoxicity in all three groups.

CONCLUSIONS

TAE with (188)Re-HDD-labeled iodized oil has potent antitumor effect in VX2 liver tumor that is comparable with that of TACE with an established chemotherapeutic agent.

90Y-oxine-ethiodol, a potential radiopharmaceutical for the treatment of liver cancer

Ethiodol (or lipiodol) is selectively retained in hepatocellular carcinoma and is used as a vehicle to deliver radioactive agents following intraarterial hepatic infusion. We prepared the lipophilic complex 90Y-oxine with a radiolabeling efficiency of 97.6+/-1.1%. After extraction into ethiodol, a stability test in serum at 37 degrees C showed that 87.8% of the 90Y remained ethiodol-bound for 7 days. Bremsstrahlung imaging of a rabbit for 48 h confirmed that the homogeneous mixture of radiolabeled 90Y-oxine and ethiodol stayed in the targeted liver lobe. This radiopharmaceutical is thus a potential candidate for the treatment of non-resectable liver cancer.

Intra-arterial radionuclide therapy for liver tumours: effect of selectivity of catheterization and 131I-Lipiodol delivery on tumour uptake and response

Several authors have demonstrated the good tolerance of hepatic intra-arterial 131I-Lipiodol therapy and report survival rates of 21-25% after 1 year in inoperable patients. This study explored the possibility that more selective hepatic arterial instillation could be a strategy for increasing tumoural uptake and response of 131I-Lipiodol. Between June 1999 and September 2001 we selected 24 patients: 14 received a selective instillation of 131I-Lipiodol to the proper hepatic artery (SEL group); and 10 received a hyperselective instillation in the right or left hepatic artery (HYP-SEL group). The individual 131I-Lipiodol activity as a per cent of the injected activity per millilitre of tumour (%IA/ml tumour) was correlated with the selectivity of instillation in 28 tumours and with tumour response in 24 tumours. Differences in tumour response or tumour uptake between the SEL and HYP-SEL groups were not significant. In general, we observed a %IA/ml tumour of 0.05-2.6% for the uptake of 131I-Lipiodol. The uptake was significantly higher in responsive disease than in stable or progressive disease (P=0.002). A large tumour volume was invariably related to low uptake of 131I-Lipiodol and progressive disease (P=0.008). In conclusion, our study does not support the general use of hyper-selective or super-selective intra-arterial administration of 131I-Lipiodol. This result may be extrapolated to similar types of intra-arterial, loco-regional hepatic radionuclide therapy.

Implantation of VX2 carcinoma into the liver of rabbits: a comparison of three direct-injection methods

The efficacy of agarose in preventing VX2 carcinoma cell leakage was evaluated and the results were compared with two traditional methods. Forty-five rabbits were divided into 3 groups: Group 1, VX2 tumor cells were injected directly into the liver and no special procedure after removal of the needle; Group 2, the puncture site was gently compressed, using an alcoholic cotton gauze, for three minutes; Group 3, 0.2 ml of heated liquid agarose was injected to seal the aperture after injection of VX2 cells. The leakage rates were 80%, 53.3% and 6.6% for group 1, group 2 and group 3, respectively. We consider agarose is a useful material in preventing the leakage in the establishment of VX2 liver tumor models.

Synthesis of 188 Re-labelled long chain alkyl diaminedithiol for therapy of liver cancer

Radioisotope-labelled lipiodol has been used in the therapy of liver cancer. Recently a lipiodol solution of 188Re-labelled diaminedithiol (DD) has been reported to show a high uptake in the liver cancer. We synthesized long-chain alkyl DD derivatives to improve their uptake and retention in tissue. As the length of the alkyl chain increased, tissue uptake and retention also increased due to hydrophobic interaction with lipiodol. Among the synthesized compounds, the lipiodol solution of 188Re-HDD, the DD derivative with the longest side chain (C16), is a promising agent for therapy of liver cancer.

131I lipiodol therapy for unresectable hepatocellular carcinoma

BACKGROUND

More than 80% of hepatocellular carcinoma tumours (HCC) are unresectable at presentation because of the multicentric nature of the disease or the severity of liver disease. Arterially administered lipiodol is preferentially retained by HCC and has been used as a vehicle for delivery of therapeutic agents to the tumour. The aim of this phase I study is to present the experience with 131I-labelled lipiodol in the treatment of unresectable HCC.

METHODS

131Iodine lipiodol treatment was administered to 12 patients with unresectable HCC between 1994 and 1999. The outcome of treatment in these patients was evaluated for survival, clinical tolerance, liver function tests, alpha-fetoprotein (AFP) levels and changes in tumour size on computed tomography (CT) scans.

RESULTS

Ten of the 12 patients received more than one 131I treatment. Five patients had treatment for post-resection recurrence. Serum AFP levels dropped initially in five of the seven patients with elevated values. Tumour size, evaluated by CT scans at 3 months, decreased in six patients and remained stable in the rest, except one patient in whom both the AFP level and tumour size had increased. Using life table analysis, the 50% survival was 19 months.

CONCLUSIONS

Intra-arterial 131I treatment was very well tolerated. A reduction in AFP levels and tumour size occurred in half of the patients and resulted in a 50% probability of survival of 19 months. Further examination of the value of this treatment in phase II and III studies is required.

Lipiodol solution of a lipophilic agent, (188)Re-TDD, for the treatment of liver cancer

Radiolabeled lipiodol has been used for targeting liver cancer. We developed a lipiodol solution of (188)Re-TDD (2,2,9,9-tetramethyl-4,7-diaza-1,10-decanedithiol) and investigated its feasibility for the treatment of liver cancer. The lipiodol solution of (188)Re-TDD was well-retained in the lipiodol phase in vitro. After injection through the tail veins of mice, high lung-uptake was investigated which is evidence of embolizing activity. We also found high accumulation in hepatoma after injection through the hepatic arteries of hepatoma-bearing rats. In conclusion, the lipiodol solution of (188)Re-TDD is a promising agent for liver cancer therapy.

A comprehensive study on the blockage of thyroid and gastric uptakes of 188Re-perrhenate in endovascular irradiation using liquid-filled balloon to prevent restenosis

188Re-perrhenate has been reported effective in preventing restenosis after percutaneous transluminal coronary angioplasty. However, if the balloon ruptures, 188Re-perrhenate is released into the circulation, causing high radiation dosing to the thyroid and stomach. In this study, we evaluated the effects of perchlorate or iodide given at different times and in different ways for blocking the uptake of 188Re-perrhenate in the thyroid glands and the stomach to find the best method to apply clinically to reduce the radiation dose in case of balloon rupture. Sodium perchlorate, sodium iodide, or potassium iodide was given orally or intravenously to rats before, during, and after the injection of 188Re-perrhenate. The rats were sacrificed and we calculated the concentration of 188Re-perrhenate in various organs to evaluate the preblocking, mixed formula, and postblocking effects of perchlorate or iodide. Our data showed that the preblocking method effectively reduced the uptake of 188Re-perrhenate in both the thyroid and the stomach. The mixed formula method also demonstrated good blocking effect. The postblocking method showed obvious depression of thyroid uptake of perrhenate but its blocking effect on the stomach was not satisfactory.

Comparison of various rhenium-188-labeled diphosphonates for the treatment of bone metastases

In the past, many diphosphonates were introduced as bone scan radiopharmaceuticals. In addition, diphosphonates have been labeled with beta-emitted isotopes and developed into useful therapeutic drugs for bone metastases. However, it is not clear which diphosphonate is the best choice when labeling with Re-188. In this study, we labeled methylene diphosphonate (MDP), hydroxyethylidene diphosphonate (HEDP), and hydroxymethane diphosphonate (HDP) with Re-188. Each radiopharmaceutical was further evaluated in two conditions (with and without carrier). Twenty-four rabbits were used (four in each group) for the analysis of the biodistributions and bone uptakes of these radiopharmaceuticals to assess their potential for clinical applicability. Four hours after intravenous injection of approximately 37 MBq (1 mCi) Re-188-labeled diphosphonate preparations, whole body scans were performed using a large-field gamma camera equipped with a high resolution collimator. Bone-to-soft tissue ratios (B/S ratio) were calculated using a computer program. Our data showed that Re-188 HEDP with carrier (10(-4) M carrier) could accumulate in the skeletal system whereas very little absorption by bone was observed in the rabbits that were injected with carrier-free Re-188 HEDP. In addition, no significant bone uptake was demonstrated for Re-188 MDP or Re-188 HDP, with or without carrier. The B/S ratio was 25.06 in the Re-188 HEDP with carrier group but less than 3 in the other groups. In conclusion, HEDP is the best choice among these three bone-seeking drugs when labeled with Re-188. But, it is necessary to add carrier when preparing Re-188 HEDP for the treatment of bone metastases.

Rhenium-188-Labeled DTPA: a new radiopharmaceutical for intravascular radiation therapy

Balloon angioplasty is a standard treatment for artherosclerotic coronary artery disease. However, its clinical value is reduced by a high restenosis rate. A new concept in preventing restenosis is the use of a liquid-filled balloon containing a beta-emitting radioisotope. In this study, we performed biodistribution studies of Re-188 perrhenate and Re-188 diethylenetriaminopentaacetate (DTPA) to assess the resulting organ dose values in the event of balloon rupture if these agents are used for the clinical inhibition of restenosis after percutaneous transluminal coronary angioplasty (PTCA). After injecting Re-188 preparations intravenously, rats were killed at 10 min, 30 min, 60 min, 2 h, and 6 h (n = 5 per group). Tissue concentrations were calculated and expressed as percent injected dose per gram or per milliliter (%ID/g or %ID/mL). In addition, urine excretion and thyroid gland uptake were evaluated in rats (n = 5 per group) with a gamma camera after administration of 37 MBq (1 mCi) of each agent. Our data showed that both agents were excreted primarily via urine. However, the excretion of Re-188 DTPA was much faster than that of Re-188 perrhenate via the urinary system. The biodistribution data revealed that radioactivity levels in the stomach and the thyroid gland were high in the perrhenate group but low in the Re-188 DTPA group. The concentration levels in other tissues including lung, liver, testis, muscle, and blood were low throughout this study for both agents. The thyroid radiation value in the Re-188 perrhenate group was 0.163 mGy/MBq, which was much higher than that of the Re-188 DTPA group (0.0167 mGy/MBq). The stomach radiation value was as high as 0.127 mGy/MBq for Re-188 perrhenate, compared with 0.013 mGy/MBq for Re-188 DTPA. In conclusion, in the event of balloon rupture, the release of Re-188 DTPA results in lower radiation doses than Re-188 perrhenate, especially to the thyroid gland and the stomach. Our data suggest that Re-188 DTPA is a useful radiopharmaceutical for endovascular irradiation.

Hepatic intraarterial 131I iodized oil for treatment of hepatocellular carcinoma in patients with impeded portal venous flow

PURPOSE

To evaluate the efficacy and safety of intraarterial hepatic iodine 131 iodized oil for treatment of hepatocellular carcinoma in patients with impeded portal venous flow.

MATERIALS AND METHODS

Twenty-four patients (mean age, 61 years) with hepatocellular carcinoma underwent 38 courses of 131I iodized oil (one to three per patient), with a mean dose of 2,146 MBq injected into the proper hepatic artery. Hepatocellular carcinoma manifested as single nodules (n = 8; mean, 7.75 cm), multiple nodules (n = 13; mean, 5.46 cm), or a mass (n = 3) occupying more than two hepatic segments. Portal venous thrombosis was complete (n = 10), right (n = 9), left (n = 2), or multisegmental (n = 1). Two patients had hepatofugal portal flow.

RESULTS

Among the 23 patients with evaluable results, response to treatment was partial in three, and disease was stable in 12 and progressive in eight. Estimated actuarial survival rates were 70%, 33%, 12%, and 6% at 3, 6, 9, and 12 months, respectively, with two patients alive at 9 and 11 months. The median survival time was 147 days. Adverse events were the early death of one patient owing to hepatic failure and transient symptomatic hepatic failure after 12 courses in nine patients.

CONCLUSION

In this preliminary experience, intraarterial hepatic 131I iodized oil did not demonstrate high efficacy in the treatment of hepatocellular carcinoma in patients with portal venous thrombosis, as side effects were not rare.

Expression profile of vascular cell adhesion molecule-1 (CD106) in inflammatory foci using rhenium-188 labelled monoclonal antibody in mice

Rhenium (Re)-188 is a generator (W-188/Re-188) produced high energy beta-emitter suitable for radionuclide therapy (T1/2 is 16.9 hrs and Emax 2.1 MeV (range 11 mm)). We have labelled monoclonal antibody (MAb) raised against vascular cell adhesion molecule-1 (VCAM-1) with Re-188 using glucoheptonate chelation technique and SnCl2 as reducing agent. The labelling efficiency, free perrhenate and reduced Re were controlled with thin layer chromatography and the purification of Re-188-MoAbs was performed using gel filtration. Our results indicate that Re-188-labelled antibodies remain in vitro stable and the labelling purity is > 90%. We also have applied these Re-188-MoAbs for detection of inflammatory disease in a mouse. The effective half-lives of organs of interest after an injection of Re-188-anti-VCAM1 were as follows: blood 5.2 hr, kidney 4.7 hr, and liver 9.6 hr. Re-188-anti-VCAM-1 was found to accumulate mainly in kidney and liver. One hour after the injection, the kidney contained in average as high as 12.5% and the liver 2.8 ID/g tissue. After 6 hr, the kidney contained 5.5% ID/g and the liver 2.6% ID/g. At 24 hr, the kidney uptake was 0.5% ID/g and the liver uptake 0.8% ID/g, respectively. The inflamed foci, subcutaneous lesions in the footpad skin, were visualized using gamma camera. From the distribution data the uptakes in the inflamed foci as follows: at 1 hr 2.18 (inflammation) and 1.72% ID/g (control), at 6 hr 1.42 (inflammation) and 0.85% ID/g (control), and at 24 hr 0.17 (inflammation) and 0.084% ID/g (control), respectively. Anti-VCAM-1 MAb showed better targeting as compared to control MoAbs in inflammation (caused by E.coli lipoplysaccaride). In conclusion, Re-188 is suitable for MAb labelling, and MAb against VCAM-1 may be used for detection of local inflammatory disease.