Feasibility of tumor imaging using L-3-[iodine-123]-iodo-alpha-methyl-tyrosine in extracranial tumors

L-3-[123l]-lodo-a-methyl-tyrosine (IMT) is a modified amino acid. It is reported to be avidlytaken up in brain tumors, reflecting amino acid transport and is suitable for SPECT. Methods: To determine whether tumors outside the brain can also accumulate this tracer, we injected 300-450 MBq IMTinto 20 patients with differenttumors [5 breast cancers, 4 lung tumors (1 benign), 2 carcinoid liver metastases, 4 soft-tissue tumors (1 benign), 3 malignant lymphomas and 2 primary brain tumors]. Tumor size ranged from i—i2cm. Imaging was repeated after radiotherapy in two patients with breast cancer. Histology was available in all cases. Dynamic scans, whole body imaging and SPECT were performed during the first hour and 3 hr after injection. Plasma samples were analyzed for IMT,free 1231 and other metabolites. Results: Allprimary tumors were visualized. Tumor-to-background ratios ranged from i .i to 3.8 on planar and from 1.3to 6.2on SPECTimages.Tumoruptakepeakedin the first hour. Two carcinoid lesions in the liver tumors exhibited no IMT uptake above liver background. Tumor-to-background ratios in a benign bone inflammatoryprocess and a focal pulmonary vasculitis were less than i .2 (planar) and i .9 (SPECT)and could be differen tiated from uptake in all malignant nonbrain tumors. IMTwas rapidly cleared from the plasma [3.6% ±0.6% (mean ±s.d.) injected dose/liter at 10 mm postinjection]. Minor in vivo deiodination was present (

Keywords:

• Nuclear medicine
• Histology
• Cancer
• Excretion
• Breast cancer
• In vivo
• Lung
• Iodine-123
• Medicine
• Radiation therapy
• Pathology

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