Hope on the Horizon for Advanced Breast Cancer
New Treatments Are Prolonging Survival and Improving Quality of Life
The female hormone estrogen stimulates the growth of breast cells, including cancerous cells. So drugs that block estrogen in various ways can combat cancers that are estrogen receptor positive (ER+). In essence, the drugs "starve" the abnormal cells of the estrogen they need to proliferate. Tamoxifen (brand name Nolvadex) is the best known hormone therapy. It was the first anti-estrogen drug available for use for treating advanced breast cancer, and it works by selectively blocking estrogen's effects on breast cancer cells. (These types of drugs are called SERMs.) Another drug, Fareston, works similarly to Tamoxifen, and is available to treat advanced breast cancer. Unfortunately, not all breast cancers respond to SERMs, and others become resistant to this treatment over time.
But now, a new type of anti-estrogen drug is available. Three of these drugs are currently available -- Arimidex, Femara and Aromasin -- and each is taken in pill form. These medications promise more options for women with advanced disease -- even for those whose cancer has become resistant to Tamoxifen.
In fact, Arimidex and Femara are now approved for initial use in postmenopausal women with advanced breast cancer, rather than as a second-line of defense after Tamoxifen has failed. Arimidex has also been approved as adjuvant therapy -- drugs given after surgery or radiation -- for women with certain types of early breast cancer.
Aromatase inhibitors work differently than Tamoxifen; they actually lower the amount of estrogen the body produces. There's also evidence that they may be more effective drugs. The landmark ATAC study recently showed that Arimidex was significantly more effective than Tamoxifen in post-menopausal women with early breast cancer, and several studies have indicated that aromatase inhibitors cause less toxicity and fewer side effects than Tamoxifen.
"In terms of hormonal therapies, we now have a significant number of agents available, with new ones appearing all the time, and we can sequence them," says Isaacs.
Another anti-estrogen drug, Faslodex, is representative of a whole new class of drugs that work by destroying the estrogen receptors in cancerous breast cells. Faslodex was approved by the FDA and is now available. It's given as an injection and is approved for use in women with ER+ Tamoxifen-resistant metastatic breast cancer. At least one study shows that it may also be helpful for women who have previously received other hormonal treatments in addition to Tamoxifen, such as aromatase inhibitors.
Earlier versions of hormone therapy sometimes caused nausea, bleeding and blood clots, but those side effects have been reduced significantly with the newer drugs. "Quality of life with these drugs is much better and the side effects are much more tolerable," Isaacs says.