L-3-123I-alpha-methyltyrosine for melanoma detection: a comparative evaluation

L-3-123I-alpha-methyltyrosine (IMT) was compared to [67Ga]citrate, [203Pb]Tris and [131I]iodochloroquine (ICQ) with respect to their potential as melanoma seeking radiopharmaceuticals in two tumor lines, a malignant melanotic melanoma of the Sofia type and a malignant amelanotic melanoma of the Greene-Harvey type, transplanted onto Syrian Golden hamsters. [203Pb]Tris and ICQ showed significant accumulation only in melanotic melanoma. In contrast, [67Ga]citrate and IMT accumulated in both tumor lines. [67Ga]citrate has very high tumor-to-skin, tumor-to-eye, and tumor-to-blood ratios at 48 h after injection, but has low selectivity for melanoma and unfavorable physical (high gamma-energy) and biological (half-time) characteristics. IMT has a convenient gamma-energy at 159 keV and a short biological half-time. Maximum of melanoma accumulation is reached at 1-2h after application; tumor-to-tissue ratios are suitable for scintigraphy.