European Nuclear Medicine Guide
Radiopharmaceutical: [131I]I-Lipiodol
Nuclide: Iodine-131
Activity: Iodine-131 is a beta emitting radionuclide with a physical half-life of 8.04 days. The maximum and mean β particle energies are 0.61 MeV and 0.192 MeV, respectively. Iodine-131 emits a principal γ photon of 364 keV (81% abundance). The specific activity is 1.1 GBq/ml at calibration.
Administration: [131I]I-Lipiodol is supplied in solution for hepatic intra-arterial injection.
After hepatic intra-arterial injection, [131I]I-Lipiodol follows arterial flow towards the tumour and is trapped in tumour microvessels. The remainder distributes in normal liver. 24 h post administration, 75-90% of administered activity is trapped in the liver. 10-25% pulmonary uptake results from arteriovenous shunting. After 24 hours, tumour to normal liver uptake ratios range from 2.3 and 12. There is no recirculation. Tumour and normal liver effective half-lives are 5.5 and 3.5 days, respectively. A slight increase in lung activity occurs for 48 hours post administration, followed by a decrease with an effective half-life of 4-5 days. Excretion is predominantly renal (30-50% within 7 days). Faecal excretion is low (3% in 5 days).
Histologically confirmed, inoperable primary hepatocellular carcinoma (HCC).
Absolute contraindications:
Relative contraindications:
The facilities required will depend on national legislation. The patient should be admitted to an approved isolation facility comprising an appropriately shielded room and adjoining bathroom facilities. The administration of [131I]I-Lipiodol should be undertaken by appropriately trained medical staff with supporting scientific and nursing staff.
Patients considered for [131I]I-Lipiodol therapy will be ineligible for or will have failed conventional first line treatment.
Pre-treatment assessment of tumour volume and serum tumour markers is essential.
[131I]I-Lipiodol is supplied in solution for use at room temperature. Lipiodol is a viscous oil which offers high resistance to syringe dispensing and catheter injection. The radiopharmaceutical may be diluted with 2-10 mL unlabelled lipiodol to increase the total injection volume.
Stability data demonstrate <5% free radioiodine within 1 week of calibration at ambient temperature. Quality control checks are not usually required prior to therapy.
[131I]I-Lipiodol should be prepared in an appropriately ventilated cabinet to avoid radio-iodine aerosol inhalation. Care should be taken to use Luerlock syringes and taps of a material which does not dissolve in lipiodol.
Treatment should be administered under safe aseptic conditions appropriate to intra-arterial injection in premises approved for unsealed source therapy. Hepatic artery catheterization should be undertaken by appropriately trained interventional personnel.
The radiopharmaceutical is administered by slow intra-arterial injection under fluoroscopic control following conventional hepatic arteriography. The catheter is positioned accurately depending on the vasculature and position of the tumour target(s). Tumour vascular access must be achieved without risk of systemic overspill via arteriovenous malformations or aberrant vasculature.
A standard activity of 2.22 GBq (60 mCi) [131I]I-Lipiodol is injected slowly through a hepatic artery catheter via a protected glass or plastic syringe. The administered activity may be modified for medical reasons such as tumour load or according to local legislation.
The treating clinician must advise the patient on reducing unnecessary radiation exposure to family members and the public.
Following treatment, patients should avoid pregnancy for at least 4 months.
Patients should be advised of the potential side effects of [131I]I-Lipiodol therapy.
Quantitative whole-body imaging one week post therapy is recommended to confirm the distribution of [131I]I-Lipiodol. Local and whole-body activity can be expressed as percentage of administered activity and compared with an Iodine-131 standard for dosimetry calculations.
Absorbed dose estimates (obtained from a particular patient group with hepatocellular carcinoma, and might, therefore, vary with age and co-morbidity) for intra-arterial hepatic 131I-Lipiodol administration are 43 +/-22 mGy/MBq for the liver tumour, 5 +/-4 mGy/MBq for the liver parenchyma, 3 +/-1 mGy/MBq for the lungs, 0.5 mGy/MBq for the gonads, and 0.5 mGy/MBq for the whole body [189].
The activity to be administered should be checked using an isotope calibrator.
The therapeutic efficacy of [131I]I-Lipiodol derives solely from radiation as opposed to the ischemia associated with chemoembolization. 90% of the radiobiological effect results from short range β irradiation which favours destruction of tumour cells surrounding microvessels containing a high [131I]I-Lipiodol concentration.
Urinary Iodine-131 excretion is of particular concern during the first 2 days post administration. Patients should be advised to observe rigorous hygiene to avoid urine contamination.
Usual arteriography precautions should be observed before and after the procedure including correction of clotting disorders and use of an arterial plug or compression bandage after catheter removal.
Early side effects include:
Delayed side effects include:
[131I]I-Lipiodol is approved for radioembolization, although it has been largely replaced by [90Y]Y-microspheres.