Faslodex Safe, Effective in Estrogen-Sensitive Tumors
By Laurie Barclay, MD
WebMD Medical News
Reviewed by Dr. Gary D. Vogin
Dec. 6, 2000 -- In the war against breast cancer, the new drug Faslodex may be an effective weapon, according to research presented at the 23rd Annual San Antonio Breast Cancer Symposium under way this week.
"Faslodex represents a new class of [hormone] therapy that clinicians can add to their armamentarium in treating patients with metastatic disease," lead researcher C. Kent Osborne, MD, a professor of medicine at the Baylor College of Medicine Breast Care Center in Houston, tells WebMD.
According to the American Cancer Society, each year more than 10,500 women are diagnosed with metastatic, or advanced -- meaning that the disease has spread from the breast to other organs -- breast cancer. About one-third of women currently diagnosed with breast cancer go on to develop advanced breast cancer during their lifetime.
Many breast cancers are sensitive to estrogen, a naturally occurring female hormone that can be influenced by drugs like tamoxifen. Unlike traditional chemotherapy, these drugs are not associated with debilitating side effects such as hair loss, nausea and vomiting.
In two large multicenter studies, one in North America and the other in Europe, Faslodex was at least as safe and effective as Arimidex, a commonly used treatment in women whose breast cancer has spread to other parts of the body despite treatment with tamoxifen.
"The results show that Faslodex is as active as Arimidex in controlling metastatic breast cancer," says Matthew Ellis, MD, PhD, clinical director of the Duke University Breast Cancer Program in Durham, N.C., who reviewed the findings for WebMD.
The North American study headed by Osborne followed 400 postmenopausal women with breast cancer that spread while they were taking tamoxifen. Half were treated with Arimidex pills taken once daily, and half got an injection of Faslodex once each month. Neither the patients nor the researchers knew which drug the patients were taking until the study was over. In patients taking Faslodex, positive response to the drug lasted almost twice as long as it did in patients taking Arimidex (19 months compared with 10 months).
"Faslodex is a second line treatment in patients who have already failed tamoxifen," senior researcher Aman Buzdar, MD, a professor of medicine in breast medicine oncology at the MD Anderson Cancer Center in Houston, Texas, tells WebMD. "Remission was almost twice as long as in patients given Arimidex, making it another treatment option for patients with advanced breast cancer."
Only 2.5% of patients in either group had to stop taking the drug because of side effects, which included hot flashes, gastrointestinal upset, weight gain, and vaginal infections.
"Other than needing an injection once monthly, side effects are minimal," Buzdar says.
Although the study conducted by A. Howell at Christie Hospital in the U.K. and by investigators at seven other European centers was similar, the patients and researchers knew which drugs were being given during the study. More than 450 postmenopausal patients with advanced breast cancer were given either Faslodex or Arimidex. Patients receiving Faslodex were about one-third more likely to do better than patients on Arimidex. Positive response to the drug lasted about 14 months in both groups, and side effects were similar to those seen in the North American study.
"These studies offer promising results to patients with breast cancer, not only in terms of survival time but also in quality of life," Carlos Hermenegildo, MD, PhD, tells WebMD. "But there is still a long way to go until Faslodex will be used in general practice," says Hermenegildo, an assistant professor at the University of Valencia in Spain.
Unlike other drugs that affect estrogen levels, Faslodex has no increased risk of endometrial cancer affecting the uterine lining, according to Hermenegildo's research published in the June issue of Human Reproductive Update.
While Faslodex is not yet commercially available, Buzdar explains that it probably will be in about six months, based on these two large studies designed to meet standards for FDA approval.
"This is only the beginning of the Faslodex story," Ellis says. When new drugs are clinically active in patients resistant to tamoxifen, it suggests that they may ultimately prove to be even more effective than tamoxifen when given earlier. "Faslodex could prove to be a very exciting drug."
Future studies will compare Faslodex directly with tamoxifen in patients with metastatic disease, and other studies will explore its use immediately after mastectomy, Osborne says.