A reevaluation of an agent proposed for imaging oestrogen receptors: 17 alpha-[125I]-iodovinyl-11 beta-methoxyoestradiol-3-methyl ether ([125I]VMEME).

The metabolism of an iodinated steroid, 17 alpha-[125I]iodovinyl-11 beta-methoxyoestradiol-3-methyl ether ([125I]VMEME), previously proposed as a potential agent for imaging oestrogen receptor-containing tissues, has been studied and the conditions for synthesis and labelling redefined. It is confirmed that, although the compound does not itself have significant receptor-binding affinity, a metabolite is active. Because of its high solubility in fat and the consequential low contrast of small receptor-containing tumours, there is little prospect of successful early imaging of small axillary or internal mammary lymph node metastases from human breast cancer with this compound. Some more general implications of this finding are considered.