PET scan spots breast-cancer receptors.

PET scan spots breast-cancer receptors

Medical researchers see no shortage of applications for positron emission tomography (PET), the imaging technique that pinpoints with near-psychedelic artistry tiny biochemical targets in living patients. The procedure, mostly applied in the brain so far, can map the location of specific chemical receptors by illuminating -- within one to two hours -- the "parking places" of injected, radioactively labeled compounds.

Now scientists have designed a traceable, "hot" analogue of the female hormone estrogen that allows them to distinguish between the two major types of breast tumors -- those with estrogen receptors and those without. The former are often responsive to relatively innocuous drugs that block the tumor-enhancing effects of estrogen. The latter require more aggressive treatment as soon as possible.

Until now, cancer specialists had no way of differentiating between the two tumor types in vivo. Researchers can measure estrogen-receptor densities on biopsied specimens. But with secondary, or metastatic, tumors often difficult to find or biopsy -- and with many metastases lacking estrogen receptors even when the primary tumor may have many -- months could pass before a physician finds that anti-estrogen therapy is not working.

Michael J. Welch and his colleagues at the Washington University School of Medicine in St. Louis and John A. Katzenellenbogen of the University of Illinois in Urbana-Champaign injected into 10 women diagnosed with breast cancer an estrogen analogue containing positron-emitting fluorine-18. As confirmed by laboratory tests on biopsied specimens, they correctly identified breast tumors with estrogen receptors as well as estrogen-receptor-rich metastatic tumors in the lymph nodes and the chest wall. Ongoing tests will tell whether PET data can predict the success of estrogen-blocking therapies, the researchers report in the October RADIOLOGY.