Breast cancer is one of the most common types of cancer diagnosed in women today, second only to non-melanoma skin cancers. As we have learned more about breast cancer, there have been many advances in multi-pronged approaches to treatment that have improved outcomes for many women. Since estrogen is found to be a factor in two-thirds of breast cancers, hormone treatment therapies play an important role in prescribed treatments, in addition to the traditional treatment methods such as chemotherapy, radiation and surgery. Thanks to increased awareness and research about breast cancer, several hormone treatment options have come to the market in recent years.
The most well-known hormone treatment for breast cancer is Tamoxifen. It is an anti estrogen drug, in pill form, that is usually taken for 5 years following tumor removal surgery. It has been shown to reduce the incidence of reoccurrence of the cancer by about 50% for women with early breast cancer if the cancer contained estrogen or progesterone receptors. It is also used to treat metastatic breast cancer and to prevent the development of breast cancer in high-risk women.
No hormone treatment is without risk. Tamoxifen can increase the risk of endometrial cancer (cancer of the lining of the uterus). It can also increase the risk of uterine sarcoma, a rare cancer of the connective tissue of the uterus. Blood clots are another possible side effect of Tamoxifen. Less serious side effects of this hormone treatment weight gain, hot flashes, vaginal discharge and mood swings. Still, for most women with early breast cancer, the benefits of taking Tamoxifen outweigh the risks.
Toremifene is another anti-estrogen drug closely related to Tamoxifen. Toremifene may be used in postmenopausal women with breast cancer that has metastasized. It is an anti-estrogen medicine that is used in tumors that are estrogen-receptor positive or whose estrogen-receptor status is unknown.
Similar to Toremifene and Tamoxifen, Fulvestrant is a newly approved drug that also acts via the estrogen receptor, but instead of blocking it, Fulvestrant drug eliminates it. Research about breast cancer treatments has shown it is often effective even if the breast cancer is no longer responding to Tamoxifen. It is given by injection once a month, but is only used in women who are already in menopause. The major side effects associated with this hormone treatment are hot flashes, mild nausea and fatigue.
There are three additional drugs traditionally used to stop estrogen production in postmenopausal women that have been approved for use in treating both early and advanced breast cancer. These drugs, Femara, Arimidex and Aromasin, work by blocking the enzyme aromatase, which is responsible for producing small amounts of estrogen in postmenopausal women. They can only be used in postmenopausal women because they cannot stop the ovaries of premenopausal women from producing estrogen.
In terms of effectiveness, these drugs have been compared with Tamoxifen as adjuvant hormone treatment in postmenopausal women with early breast cancer. Clinical trials have been performed comparing Tamoxifen with one of the aromatase inhibitors for a total of 5 years, or after either 2 years or 5 years of Tamoxifen treatment. Each study has shown an advantage to using either the aromatase inhibitor instead of Tamoxifen for a total of 5 years or following several years of Tamoxifen, as opposed to keeping women solely on Tamoxifen for a full 5 years. These aromatase inhibitors are often a first choice because they have fewer side effects than Tamoxifen. The incidence of blood clots is rare and there is no connection to endometrial cancer. However, these aromatase inhibitors can cause osteoporosis and bone fractures because they remove all estrogens from a postmenopausal woman.
For those women who do not have breast cancer, but are looking to learn more about breast cancer risks, the estrogen connection is still important to understand. Historically, estrogen replacement therapy has been used to combat the effects of menopause, including hot flashes, vaginal dryness and loss of libido. However, in 2002, the link between an increased risk of breast cancer (as well has heart attack and stroke) and estrogen replacement therapy was made public. Therefore, those concerned about breast cancer, particularly those in higher risk groups, should avoid estrogen replacement therapy.
As research continues about breast cancer, we should expect even more adjuvant therapies to become available. The greatest hope would be not just a treatment for breast cancer, but a cure. With enough funding and time, hopefully we will one day find it.