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Estradiol SPECT Shows Promise in Spotting Early Breast Cancer

Estradiol SPECT Shows Promise in Spotting Early Breast Cancer

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 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 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.

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