Hepatocellular carcinoma (HCC) is the 5th most common tumour worldwide and has a dark prognosis. For nonoperable cases, metabolic radiotherapy with Lipiodol labelled with
Hepatocellular carcinoma (HCC) is the fifth most common tumour worldwide and even ranks second in terms of mortality [
First attempts to label Lipiodol with radioisotopes other than iodine-131 were done with a covalently bond chelate, with disappointing results [
Previous studies at the ENSCR led to the preparation of a new class of complexes with perthiobenzoate and dithiobenzoate moieties [M (PhCS3)2 (PhCS2)] which structure is given in Figure
Superposition of the crystal structures of 185/187Re-SSS and 99Tc-SSS complexes (reprinted from: N. Lepareur, Ph.D. thesis no. 2003 REN 10110, 2003).
The SSS complex was subsequently prepared with technetium-99 m, using a freeze-dried kit method (containing 0.75 mg tin chloride, 75 mg calcium gluconate, and 25 mg sodium chloride, diluted 1/10), initially in a view of lymphocytes labelling [
Synthesis of 99mTc-SSS.
It was, therefore, a good candidate to label Lipiodol. The method previously described by Jeong et al. [
Rhenium-188 is obtained in the form of perrhenate by elution of a 188W/188Re generator, similar to the 99Mo/99mTc generator. The major difference lies in the necessity of postelution concentration to obtain high-volumic activity (up to 20 GBq/mL with a 37 GBq generator), due to the lower specific activity of 188 W compared to 99Mo, necessitating a bigger alumina column (see Figure
188W/188Re generator and its remote-controlled elution/concentration system (IRE, Fleurus, Belgium).
Kit formulation: 0.8 mg SnCl2·2H2O (dissolved in 0.1 mL HCl 1 M), 7.5 mg sodium gluconate, 30 mg ascorbic acid, and 40 mg potassium oxalate. This freeze-dried kit is reconstituted in 0.5 mL saline, and the perrhenate (0.5 mL of saline) is then added. After 15 min at room temperature, 20 mg of sodium dithiobenzoate is added, and the solution is heated for 30 min at 100°C, to provide the 188Re-SSS complex, as a precipitate. 2-3 mL of Lipiodol is added to the mixture, which is then centrifuged, as previously described with technetium-99 m. 188Re-SSS/Lipiodol was obtained with a
A new efficient and stable labelling of Lipiodol was described. However, for activities above 1850 MBq (therapeutic activities), the labelling yield decreased dramatically. Consequently, the synthesis had to be further improved, in view of HCC treatment. Kit formulation was tuned, and reaction conditions were slightly modified.
A freeze-dried kit (4 mg SnCl2·2H2O (dissolved in 0.1 mL HCl 1 M), 30 mg sodium gluconate, 30 mg ascorbic acid, 40 mg potassium oxalate) is reconstituted in 0.5 mL saline, and the perrhenate (0.5 mL of saline) is then added. After 15 min at room temperature, 40 mg of sodium dithiobenzoate is added, and the solution is heated for 15 min at 100°C, to provide the 188Re-SSS complex, as a precipitate. 2-3 mL of Lipiodol is added to the mixture, which is then stirred with a vortex. After 10 min of centrifugation (2200 g), both phases are separated, and the lower phase (radiolabelled Lipiodol) is carefully recovered. 188Re-SSS/Lipiodol is obtained with a
Having to handle high activities of 188Re to prepare therapeutic doses can result in an excessive radiation exposure to the operator, and particularly at the finger tips [
TADDEO module (COMECER, Castel Bolognese, Italy).
Flowchart of the TADDEO module for the preparation of 188Re-SSS/Lipiodol.
The foremost gain of the automation was in the dose received by the operator. This is particularly true for the dose to the extremities. Impact of the automation was studied with thermoluminescent dosimeters (TLD) fixed at the finger tips, and, respectively, 80 and 58% decreases in the right-hand and left-hand doses were shown [
Mean dose equivalents (mSv/GBq) for both hands for manual (
Good targeting and stability of radiolabelled Lipiodol were investigated
99mTc-SSS/Lipiodol could be useful for carrying pretherapeutic dosimetry studies, as is performed with 99mTc-MAA for 90Y-labelled microspheres [
188Re-SSS/Lipiodol was also investigated in healthy pigs [
Scintigraphic scans of 188Re-SSS/Lipiodol 48 h after intra-arterial injection in healthy pigs.
Fused autoradiography/histology tissue stain of the liver, 1 h after intra-arterial injection of 30 MBq of 188Re-SSS/Lipiodol. Radioactivity (black spots) is weakly noticeable in the region of hepatic artery and portal space (big yellow arrow) and strongly in capillary sinusoids (small yellow arrow), May Grumwald Giemsa coloration,
Unfortunately, no porcine model of hepatocarcinoma was described, and attempts to develop one with human hepatocarcinoma cells in immunodepressed pigs with cyclosporine gave no results. On the contrary, murine hepatoma models are well documented. It was thus decided to investigate the tumour uptake of 188Re-SSS/Lipiodol in rats inoculated with N1S1 hepatocarcinoma cell line [
Results showed preferential hepatic uptake, with a weak to moderate pulmonary uptake, and, most importantly a good tumour retention (Figure
To assess the safety of the radiotracer, a toxicity study—acute and chronic—has been undertaken in dogs (Beagles), with the nonradioactive analogue 185/187Re-SSS/Lipiodol, prepared in the same conditions as for clinical preparation (sterile GMP kits, same amounts of reactants, remote-controlled procedure). The Re-SSS/Lipiodol was injected for less than 24 h after preparation.
The study comprised two phases. For the first phase (7 days), animals (3 males + 3 females) received a single injection at D1, and for the second one, animals (2 males + 2 females) received one dose at D1 and one at D30. Control group (5 males + 5 females) received Lipiodol alone. Some results are summarised in Figures
Physiological parameters; toxicity study in dogs (
Some clinical chemistry values; toxicity study in dogs (
This study thus demonstrated lack of toxicity of Re-SSS/Lipiodol, opening the way for the injection in human.
Files were submitted to the relevant authorities, that is, French Agency for the Safety of Health Products (AFSSAPS), French Nuclear Safety Authority (ASN), and Ethical Committee (
Scintigraphy (a) showing intense hyperfixation (in black) in 4 tumour foci, CT scan (b) showing intense Lipiodol retention (in white) in the nodules and fusion image (c) of scintigraphy and CT scan; 71-year-old male, 1 h after injection of 1.85 GBq of 188Re-SSS/Lipiodol. Transverse, sagittal, and coronal views.
In conclusion, we have developed a potential HCC treatment by radioembolisation, with a phase 1 clinical trial currently in progress. This represents almost ten years of multidisciplinary research, from basic chemistry to clinic. Its clinical relevance has now to be demonstrated, and its efficiency and tolerance have to be compared to other existing therapeutic options.
The authors declare that they have no conflict of interests.
The authors gratefully thank all those who supported this scientific project since its debuts, all the coauthors of papers, and the students who contributed to the project. They also thank their supervision authorities, as well as the region Brittany, ARC, French League against Cancer, and the Cancéropôle Grand-Ouest for their financial support. This paper was partly the object of an oral presentation at the EANM, 2011 in Birmingham.