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 131 I and 188 Re, (2) lipiodol labelled with 131 I alone and (3) lipiodol labelled with 188 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 22MBq of 188 Re-SSS lipiodol and 7MBq 131 I-lipiodol. Group 2 received 14MBq 131 I-lipiodol. Group 3 received 44MBq of 188 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 rmixture of 188 Re-SSS lipiodol and 131 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 131 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 188 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, 131 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 131 I-labelled lipiodol by 188 Re-labelled lipiodol. However, this study clearly demonstrated that, for small tumours, as in an adjuvant setting for exemple, 131 I-labelled lipiodol should be a better option than 188 Re-labelled lipiodol.