A new treatment for advanced breast cancer in women who have hormone-sensitive tumors, called fulvestrant, works when tamoxifen is no longer effective, according to a new study.

Researchers reported their results on this successful drug therapy in articles and an editorial in a recent issue of the Journal of Clinical Oncology (Vol. 20, No. 16: 3365-3368, 3386-3395, 3396-3403). Fulvestrant (Faslodex) is made by AstraZeneca.

Fulvestrant is the same type of drug as tamoxifen, which is commonly used in treating women who have breast cancer or are at high risk of developing the disease.

Fulvestrant, an anti-estrogen drug, is given by injection once a month.

The studies were performed by two different groups of researchers. The first team, led by C. Kent Osborne, MD, included doctors from a number of cancer centers in the US and Canada. The second group, led by Anthony Howell, MD, at the Christie Hospital, Manchester, UK, studied patients from Europe, South Africa, and Australia.

The two studies were essentially alike. The two groups treated a total of 950 postmenopausal women.

These women had progression of their disease and needed treatment. All of the women had received tamoxifen in the past. Some women had received tamoxifen as adjuvant (preventive) treatment after breast cancer surgery and radiation. Other women had received tamoxifen after their disease recurred and the cancer was progressing despite the tamoxifen therapy.

Many, but not all, of the women had their breast cancer tested for hormone receptors. Most of the women were hormone-sensitive.

About half the women were given fulvestrant, and the other half anastrozole (which is taken by mouth). In the North American trial, women received a drug and a placebo, which is an inactive treatment, not a drug. This means that woman on fulvestrant received the fulvestrant shot and placebo pill (which looked like anastrozole). Women assigned to the anastrozole group were given an anastrozole pill and a placebo shot.

The results of both trials were nearly alike. When compared to the women taking anastrozole, the women on fulvestrant had the same results.

The two drugs were equally effective. Women tolerated both drugs equally well, with few side effects. Quality of life for women on both drugs was the same.

The authors concluded that fulvestrant was at least as effective as anastrozole in women who had previously taken, and failed, tamoxifen therapy.

While fulvestrant is an estrogen blocker similar to tamoxifen, it works slightly differently. Instead of just blocking the hormone receptors on the surface of the breast cancer cells, it actually destroys the receptor.

What is especially exciting, according to the authors, is that fulvestrant is a new treatment option for women with advanced breast cancer when tamoxifen doesn't help.

I. Craig Henderson, MD, at the University of California San Francisco, wrote an editorial about the studies in the same issue of the journal. He said that doctors now have new information that may change their thinking about the treatment of breast cancer that is sensitive to hormones.

Henderson quoted author Gertrude Stein's famous saying, a "Rose is a rose is a rose." This is the same thing doctors used to say about hormone therapy in breast cancer, noted Henderson, that "Endocrine therapy is an endocrine therapy is an endocrine therapy."

One hormone therapy was the same as another, said Henderson. And no hormone treatment was ever found to be better than another.

As a result, one hormone treatment was used after another, Henderson said in his editorial. Doctors would simply use the one with the fewest side effects first.

But the past few years have provided new hope to women with breast cancer, Henderson said.

New drugs, called aromatase inhibitors (such as anastrozole) are equal to, or perhaps better than, tamoxifen.

"Aromatase inhibitors are now clearly the treatment of choice for patients with newly diagnosed metastases (spread) from hormone-sensitive tumors," wrote Henderson. "They are effective in both tamoxifen-naïve patients (those who have never received tamoxifen as part of their treatment program) as well as those who have responded and then progressed while or after receiving adjuvant (preventive) tamoxifen."

"While these new therapies may be confusing to clinicians (doctors) and patients at this time, they also offer promise of much more effective, nontoxic treatment that will both palliate (ease) symptoms and prolong the lives of patients with breast cancer," concluded Henderson.