Dosimetric evaluation and therapeutic response to internal radiation therapy of hepatocarcinomas using iodine-131-labelled lipiodol.
OBJECTIVE
Vectorized internal radiation therapy using lipiodol-labelled with iodine-131 (131 I-lipiodol) is an effective treatment for inoperable hepatocellular carcinomas. However, few dosimetric data are available based on this approach. We have developed a dosimetric protocol based on scintiscan imaging and that is designed to calculate the tumoural absorbed dose during the treatment of hepatocarcinoma by 131 I-lipiodol.


METHODS
This concept was developed on a gamma-camera coupled to a computed tomography scanner. It integrates corrections for attenuation phenomena, scattering and dead time. The tumoural absorbed dose calculation was carried out according to the Medical Internal Radiation Dose Committee formalism. This protocol was applied to a series of 41 patients in the framework of a retrospective study.


RESULTS
The mean tumoural absorbed dose with the first treatment is 248 Gy (+/-176), as opposed to 152 Gy (+/-122) during the second. We highlighted a correlation between the tumoural absorbed dose, calculated in tomographic mode, and the morphological response to the first treatment (P=0.0071). Moreover, a tumoural absorbed dose of 280 Gy seems to be an effective absorbed dose threshold in our population. Above this absorbed dose, 84% of the patients are responders after the first treatment, whereas no responses are recorded below this threshold.


CONCLUSIONS
These results are promising because, for the first time, they allow us to predict the effectiveness of a treatment by 131 I-lipiodol. They are required to be validated on a broader exploratory trial, including a dosimetric study of the critical organs, so an individualized dosimetry can be defined for each patient.
Becker
Stéphanie
S
Department of Nuclear Medicine, Centre Eugène Marquis, Rennes, France.
Laffont
Sophie
S
Vitry
Fabien
F
Rolland
Yan
Y
Lecloirec
Joseph
J
Boucher
Eveline
E
Raoul
Jean-Luc
JL
Herry
Jean-Yves
JY
Bourguet
Patrick
P
Garin
Etienne
E
D000368:Aged; D000369:Aged, 80 and over; D002138:Calibration; D006528:Carcinoma, Hepatocellular / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000494:pharmacology*; D007459:Iodized Oil / Q000494:pharmacology*; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods; D011877:Radionuclide Imaging; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods; D016896:Treatment Outcome
D007457:Iodine Radioisotopes; D007459:Iodized Oil