DALLAS--Estradiol scans, currently being used in research for the diagnosis of early breast cancer (see illustration on page 1), have in some cases identified breast cancer 2 years prior to diagnosis by conventional means, such as mam-mography, physical examination, and ultrasound, David F. Preston, MD, said in an interview with Oncology News International.
"We believe we are able to identify the regional estrogen-receptor excess of early breast cancer prior to histological changes as seen by the light microscope," said Dr. Preston, professor of radiology and nuclear medicine, and head of the Division of Nuclear Medicine, University of Kansas Medical Center, Kansas City.
Even tumors later labeled as estrogen-receptor negative have been seen using radiolabeled estradiol(Drug information on estradiol) SPECT (single photon emission computed tomography), he added.
In a poster presentation at the American College of Radiology's 27th National Conference on Breast Cancer, Dr. Preston described a study of 44 patients with breast cancer or a high risk of breast cancer who were referred from the oncology department or high risk breast clinic. The study, which is ongoing, has funds to enroll up to 60 patients.
After patients give informed consent, their thyroid is blocked with stable iodine(Drug information on iodine) for 3 days. Then, 40 µCi/kg of I-123 E-2 is given intravenously. This compound is a high-spe-cific-activity iodine halogen (16-alpha-iodine I-123) that is attached to iodo-estradiol 17-beta. Two hours later, standard SPECT is performed.
"There is rapid blood clearance of the estradiol following injection," Dr. Preston said. Each dose includes approximately 2.5 mCi of 123I attached to approximately 100 ng of estradiol. The greatest radiation exposure is approximately 4 rads (0.04 Gy) by the descending colon, "approximately the dose received during a barium enema," he said.
Regions of breast tissue on the scan that are found to have numerical values (counts per pixel) two times that of background lung tissue values are considered to be cancer. "Thus, the technique could offer a numerical way to diagnose early-stage breast cancer," Dr. Preston said.