Scintimetric Detection of Choroidal Malignant Melanoma with [¹²³I]-5-Iodo-2-Thiouracil

Abstract

[¹²³I]-5-iodo-2-thiouracil (¹²³I-ITU) was evaluated as a radiopharmaceutical for tumor detection in 10 patients with proven choroidal melanoma. Uptake of ¹²³I-ITU was measured with a specially designed single eye probe collimator, 24 h after administration of ¹²³I-ITU. Increased uptake in the tumor-bearing eye as compared to the fellow nontumor bearing eye was found in 7 out of 10 cases when the probe was located 3.5 cm in front of the eye (p < 0.01). By using a double pinhole collimator tests were positive in 3 out of 10 ¹²³I-ITU studies only. Tests with ¹²³I-ITU were compared with 67Ga tests in the same patients. The 67Ga tests with the single eye probe collimator were positive in 6 out of 10 cases when the probe was located 6 cm in front of the eye. With the double pinhole collimator tests were positive in 7 out of 10 67Ga studies. It is concluded that ¹²³I-labeled thiouracil is at least as useful as a radiopharmaceutical for ocular melanoma diagnosis as 67Ga-citrate, provided measurements are performed with a single eye probe.

New Thioureas and Related Substances Intended for Melanoma Targeting

“…Also 5-iodo-2-thiouracil (ITU), labeled with radioiodine for possible clinical use, is similarly localized in melanotic melanoma van Langevelde et al, 1983;Coderre et al, 1986;Yamada et al, 1988). Preliminary clinical pilot studies on patients with ocular melanoma (Franken et al, 1986) or disseminated cutaneous melanoma (Olander et al, 1991) have indicated that radioiodinated ITU might be used for gamma scintigraphy scanning.…”