Therapy of Hepatocellular Carcinoma with Rhenium-188 Lipiodol

For radionuclide therapy of hepatocellular carcinoma, there have been many attempts to label Lipiodol (an iodinated ester of popyseed oil) with therapeutic radioisotopes, including 131I, 90Y, 186Re and 188Re. 131I-labelled Lipiodol is a commercially available radiopharmaceutical that is currently used in many countries. Nonetheless, despite encouraging results, there are some disadvantages with Iodine- 131, in particular the low-energy beta and high-energy gamma emissions as well as its long half-life. Rhenium-188 is an attractive alternative, since it has a higher beta energy coupled with a shorter physical half-life. In addition, 188Re emits a 155 keV γ-ray with an abundance of 15 % suitable for monitoring biodistribution and calculating dosimetry. A further advantage is that 188Re is now conveniently produced via a 188W/188Re generator system, enabling the on-site production of 188Re-radiopharmaceuticals. Over the last few years, efforts to label Lipiodol with 188Re have led to a very active area of research. Two strategies have been studied, namely i) covalent bonding between Lipiodol and the 188Re-chelate, and ii) solubilisation of a lipophilic 188Re-complex into cold Lipiodol. While some of these approaches are currently under clinical investigation, one of them is being sponsored by the International Atomic Energy Agency. The preliminary results indicate the feasibility of using rhenium-188, which shows good tolerance and good response rates in the treatment of unresectable HCC as well as in adjuvant or neo-adjuvant settings.