Biodistribution, dosimetry and metabolism of 11 beta-methoxy-(17 alpha,20E/Z)-[I-123]iodovinylestradiol in healthy women and breast cancer patients

The biodistribution and dosimetry of the 20E and 20Z stereoisomers of 11 be ta-methoxy-(17 alpha,20)-[I-123]iodovinylestradiol (MIVE) were evaluated in six healthy women. Tumor uptake and metabolism of the 20Z isomer were eval uated in 13 women referred after abnormal mammography or after discovery of a suspect mass at physical examination. Methods: The radiopharmaceuticals were prepared from their corresponding stannyl intermediates and administra ted intravenously. Blood samples were drawn at different time intervals and urine was collected for up to 24 h. Metabolites were detected by radiochro matography. Tissue distribution was followed for up to 24 h by scintigraphi c imaging. The dosimetry was computed according to the Medical Internal Rad iation Dose scheme. Results: The 20E and 20Z isomers exhibit similar biodis tribution and dosimetry patterns. Chromatographic analysis of plasma sample s of healthy volunteers and cancer patients, as well as in vitro plasma inc ubations, confirmed the in vivo stability of (20Z)-[I-123]MIVE. Radioactivi ty was rapidly cleared from the blood by the liver and excreted through the gut, which received the highest radiation dose (0.211 mGy/MBq). The effect ive doses for the adult female and male phantom were 0.054 and 0.046 mSv/MB q, respectively. Among the 13 patients imaged with (20Z)-[I-123]MIVE, 3 had fibrocystic disease with no focal uptake, 8 had good agreement with in vit ro estrogen receptor determination and 2 were false-positive. Conclusion: T he radiation dose after intravenous administration of 20E- or (20Z)-[I-123] MIVE at imaging dose levels is within acceptable limits. There was a good c orrelation between uptake of (20Z)-[I-123]MIVE and the presence of estrogen receptors in breast cancer patients.