Dosimetric evaluation and therapeutic response to iodine-131 labelled lipiodol in treatment of hepatocellular carcinomas

Faced with increasing indications for the use of iodine-131 labelled lipiodol in the treatment of hepatocellular carcinoma (HCC), it appears essential to develop an individualized dosimetrY so we can predict the potential effectiveness of this treatment and adjust the activity to be injected. We developed a dosimetric protocol based on imagery and dedicated to calculation of the tumoral dose during the treatment of hepatocellular carcinoma by iodine-131 labelled lipiodol. This concept was developed on a SPECT- CT gantry, and integrates corrections for the phenomena of attenuation, diffusion and dead time. The dose is calculated according to the formalism proposed by the Medical Internal Radiation Dose Committee (MIRD). This protocol was applied to a series of 41 patients in the framework of a retrospective study. The results obtained in terms of biodistribution are compatible with previously published data. The total biological response rate is 42% (n= 41) for the first treatment and 43% for the second (n=25). Morphologically, there is a 17% response to the first treatment and 35% to the second. We find a correlation between the tumoral absorbed dose, calculated in tomo-scintigraphic mode, and the morphological response to the first treatment (p = 0.0071). Moreover, a tumoral absorbed dose of 280 Gy appears to be an effective dose threshold in our population. These results are promising insofar as they enable us to predict the effectiveness of the treatment by Lipiocis. (authors)