Fulvestrant Promising for Advanced Breast Ca.

SAN ANTONIO -- Fulvestrant, the first in a new class of drugs known as estrogen receptor downregulators, shows great promise for the treatment of breast cancer, oncologists asserted at a breast cancer symposium sponsored by the San Antonio Cancer Institute.

In two new phase III AstraZenecasponsored clinical trials totalling 851 postmenopausal patients with advanced breast cancer that had progressed or recurred on tamoxifen therapy, fulvestrant (Faslodex) proved at least as effective as anastrozole (Arimidex), investigators reported.

"Fulvestrant will offer a new valuable treatment option in postmenopausal women with advanced breast cancer," declared Dr. C. Kent Osborne, principal investigator in the 400-patient North American trial.

Fulvestrant is the first pure anti-estrogen. Unlike tamoxifen and other selective estrogen receptor modulators, fulvestrant has no estrogen agonist activity, he said at the meeting.

Other hormonal therapies for breast cancer aim to block the estrogen receptor or lessen the amount of available estrogen in a patient's body; fulvestrant degrades the estrogen receptor, sometimes even causing it to disapper.

"For the moment, based upon these trials, I think it would be reasonable to use fulvestrant as second-line endocrine therapy if it were available today," commented Dr. Osborne, professor of medicine at Baylor College of Medicine, Houston.

However, exactly how best to use fulvestrant in advanced breast cancer will be determined over the next 2 years through ongoing or planned clinical trials.