Carbon-11-labeled estrogens as potential imaging agents for breast tumors

• Published in: Nuclear medicine and biology 1996-05, Vol.23 (4), p.491-496
• Main Authors: Dence, Carmen S., Napolitano, Elio, Katzenellenbogen, John A., Welch, Michael J.
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Breast Neoplasms - diagnostic imaging; Breast Neoplasms - metabolism; Carbon Radioisotopes - pharmacokinetics; Carbon-11; Estradiol - analogs & derivatives; Estradiol - chemical synthesis; Estradiol - pharmacokinetics; Estrogen receptor; Female; Host-tumor relations. Immunology. Biological markers; Isotope Labeling - methods; Labeled steroids; Medical sciences; Ovary - chemistry; Radionuclide Imaging; Rats; Rats, Sprague-Dawley; Sensitivity and Specificity; Tissue Distribution; Tumors; Uterus - chemistry
• ISSN: 0969-8051; 1872-9614
• DOI: 10.1016/0969-8051(96)00029-7

We have prepared two estrogens labeled with carbon-11, 17α-[ 11C]methylestradiol and 11β-ethyl-17α-[ 11C]methylestradiol, at a specific activity of 300–1000 Ci/mmol (11.1–37 TBq/mmol), and we have determined their in vivo biodistribution in immature female rats. Both compounds accumulated selectively in two target tissues, the uterus and ovaries, reaching levels of 3.5–4.9 % ID/g at 20 min and 4.6–6.6 %ID/g at 40 min; uterus-to-blood ratios reached 12–23. Uterine uptake showed a saturation dependence with the amount of injected mass, and was displaced by unlabeled estradiol, indicating that this uptake was receptor mediated. These results suggest that these compounds may be useful in estrogen receptor-based imaging of breast tumors.