Breast Cancer FAQ’s
- Are there any good alternatives to Tamoxifen for breast cancer (after having chemotherapy and radiation therapy)?
- My mother developed breast cancer about 4 ½ years ago and so far it has not returned. She might start taking Evista (Raloxifene) for osteoporosis. I understand that this drug mimics estrogen and has not been shown to stimulate growth in breast tissue. Have there been any studies that state differently?
- If you do not have estrogen receptors, is it beneficial to take Tamoxifen following surgery and radiation treatments for breast cancer?
- My breast cancer was 97% dependent upon estrogen and 95% dependent upon progesterone. I understand Tamoxifen blocks the estrogen but don’t you need to block the progesterone also? Why do you always hear about the estrogen and not the progesterone?
- Are there benefits to staying on Tamoxifen for longer than 5 years?
- Is there a link between back pain and Tamoxifen therapy?
- What are the long-term effects of Tamoxifen?
- Is Tamoxifen a chemotherapy drug, and is it effective in preventing breast cancer?
- What can you tell me about the drug, Femara?
- Have you heard of a homeopathic remedy for breast cancer called “IP6”?
Are there any good alternatives to Tamoxifen for breast cancer (after having chemotherapy and radiation therapy)?
The majority of breast and uterine cancers are estrogen receptor positive, indicating that these cancers may be stimulated or maintained by estrogen. Fortunately, growth in estrogen receptor positive cancers may be halted by a number of agents, such as Tamoxifen as well as many other drugs that have been developed in recent years. Tamoxifen (Nolvadex) is part of a class of anti-cancer drugs known as selective estrogen receptor modulators, or SERMs. The drugs in this class, although all slightly different, block tumor growth by mimicking estrogen and filling up estrogen receptors which prevents the cancerous growth. Estrogens themselves have good effects in the body, but tend to “feed” breast and uterine cancers as well as increase the risk for blood clots. In favor of estrogen, they can relieve symptoms of menopause, have positive effects on bone density, raise the good HDL cholesterol, and lower the bad LDL cholesterol. Ideally, the perfect drug would have all of the good effects without any of the bad, but to date, no one drug alone does this. Tamoxifen blocks estrogen receptors in the breast, but mimics estrogen in the uterus, which may increase the risk for uterine cancer. There is also a potential risk of stroke and pulmonary embolism (blood clot in the lung) for women with certain types of cancer, and for women using Tamoxifen for prevention of breast cancer. Other SERMs that are available include Raloxifene (Evista) and Toremifene citrate (Fareston). Toremifene has an indication for the treatment of breast cancer that is estrogen receptor positive or of unknown status. Raloxifene is currently indicated for the prevention of osteoporosis, but there are studies currently in progress to assess the usefulness of Raloxifene in the treatment of breast cancer and to compare it against Tamoxifen (e.g. STAR Trial). The NAFTA Trial is another trial in progress that assesses the usefulness of Toremifene versus Tamoxifen. None of the SERMs treat menopausal symptoms, and may in fact increase them. Additionally, all are associated with some increased risk of blood clot formation.
Another class of drugs, aromatase inhibitors, also block the effects of estrogens. However, they work by inhibiting the production of estrogen. Cytadren (aminoglutethimide), Arimidex (anastrozole), Femara (letrozole), and Aromasin (exemestane) are currently available aromatase inhibitors, primarily used for post-menopausal women with metastatic breast cancer (cancer that has spread beyond the breast). A few studies have indicated that all of the aromatase inhibitors are at least as good as Tamoxifen, and may be better, at treating breast cancer.
Progestins are also used in the treatment of breast cancers. The most commonly used are Megace (megestrol acetate) and Provera (medroxyprogesterone). It is not completely understood how these work to stop cancerous growths, but it is thought that progestins interrupt the estrogen cycle thereby decreasing estrogen production.
The US Food and Drug Administration maintains a list of recent drugs approved for treating cancer, which can be viewed at the following link: What’s New from the Office of Oncology Drug Products
My mother developed breast cancer about 4 1/2 years ago and so far it has not returned. She might start taking Evista (Raloxifene) for osteoporosis. I understand that this drug mimics estrogen and has not been shown to stimulate growth in breast tissue. Have there been any studies that state differently?
Raloxifene is in a class of drugs called the selective estrogen receptor modulators (SERMs) and is currently only approved for the prevention of osteoporosis. These drugs selectively block certain estrogen receptors while activating others. Women have estrogen receptors in their heart, bones, reproductive organs, breast, brain, and liver. Each month, in the presence of estrogen, estrogen receptors in the breast and uterus stimulate growth and division in cells to prepare for a possible pregnancy.
Up to 50-75% of the cancers that originate in the breast or reproductive organs will have estrogen receptors. In this case, estrogen becomes a danger because it signals for the tumor to grow. Blockage of these receptors can stop or slow tumor growth in most cases. Ideally, the perfect drug would block breast and endometrial (found in the uterus) receptors, while activating them in the bone, to prevent osteoporosis; in the brain to prevent hot flashes; and in the liver and cardiovascular system to prevent cardiovascular disease and cholesterol abnormalities. Raloxifene blocks receptors in the brain, breast, and reproductive organs while activating them in the bone and cardiovascular system. This principle may be used to treat estrogen receptor positive cancers of the breast and uterus. There is good evidence to suggest it is effective in the treatment of breast cancer. Clinical studies that are evaluating Raloxifene, such as the STAR Trial (study of Raloxifene and Tamoxifen) are still in progress and the prospective results are unknown. The Multiple Outcomes of Raloxifene Evaluation (MORE) osteoporosis trial showed up to a 70% reduction in breast cancer incidence. A closer look at this study found that Raloxifene was not evaluated with respect to use for cancer and did not adequately control potential bias that may affect results concerning the treatment of cancer. No studies have found that Raloxifene will cause estrogen receptor positive tumors to grow.
If you do not have estrogen receptors, is it beneficial to take Tamoxifen following surgery and radiation treatments for breast cancer?
Everyone has estrogen receptors in their bodies. However, not all breast cancer tumors have estrogen receptors. Those tumors that do not are referred to as estrogen receptor negative. Approximately 25-50% of the patients with breast cancer have estrogen receptor negative tumors. In most cases, if the original tumor is estrogen receptor positive, recurrent tumors are likely to be estrogen receptor positive and vice versa. Tamoxifen may reduce cancer recurrence after surgery, radiation and/or chemotherapy has destroyed the original estrogen receptor positive tumor. Tamoxifen blocks these hormone receptors and inhibits the growth of estrogen receptor positive cancer cells. Studies have shown that Tamoxifen provides a benefit to women with early detection of breast cancer that is estrogen receptor positive. Studies have also shown that Tamoxifen is not effective in estrogen receptor negative tumors and should not be used.
My breast cancer was 97% dependent upon estrogen and 95% dependent upon progesterone. I understand Tamoxifen blocks the estrogen but don’t you need to block the progesterone also? Why do you always hear about the estrogen and not the progesterone?
Anti-progestins (drugs that block progesterone) are a relatively new category of anti-hormonal agents. Drugs in this class (e.g. mifepristone, RU 486) may be useful in the treatment of breast cancer. However, they are under early clinical investigation and are not approved for treatment of breast cancer. So far, the anti-progestins studied have had limited success in breast cancer clinical trials. Since Tamoxifen has been proven effective and approved for treatment of estrogen receptor positive breast cancer, you hear about this anti-estrogen drug more often than the anti-progestins.
To date, only a few randomized clinical trials have looked at the effect of long term Tamoxifen therapy. These trials looked at different indicators in the attempt to establish a cause and effect relationship between Tamoxifen use and recurrence of breast cancer. Some of the parameters studied included estrogen receptor status, Tamoxifen alone versus Tamoxifen as supplemental therapy, initial type of treatment of cancer (i.e. chemotherapy, surgical, radiation, etc) along with other possible therapies to see what works the best. Study results suggest that a small benefit may exist in using Tamoxifen for longer than 5 years. The greatest benefit was seen in patients treated for tumors that are lymph node positive and estrogen receptor positive, who received either surgery or radiation and supplemental Tamoxifen therapy. Tamoxifen therapy was associated with various adverse effects such as an increased risk of developing endometrial cancer, stroke, and pulmonary embolism (blood clot in the lung). Studies carried out for 10 years after beginning Tamoxifen therapy resulted in a small, but not significant, increase in survival rates due to recurrent disease. Study results suggest that continuation of Tamoxifen therapy beyond five years in women with node-negative breast cancer may not provide additional benefit. Additional trials are currently in progress. The duration of Tamoxifen therapy must be individualized for each patient.
Tamoxifen is a drug that is classified as an estrogen receptor blocker. It is used as part of combination therapy to treat advanced breast cancer and also to prevent breast cancer in women at high risk. Tamoxifen may cause many different side effects. One of these side effects may be a loss in bone density. This occurs as a result of blocking estrogen receptors. Estrogen plays a role in regulating the chemicals that are needed by the body to promote bone formation by increasing calcium absorption. By blocking estrogen receptors, it is possible that Tamoxifen may lead to bone loss, and studies have demonstrated that this occurs in premenopausal women.
The most common neuromuscular and skeletal side effect of Tamoxifen is increased bone and tumor pain. This pain starts shortly after Tamoxifen therapy is started, and is an indicator of good response to therapy. The pain usually resolves quickly. Generalized muscle weakness has been reported also, but there have been no published reports of Tamoxifen causing muscle spasms.
Adverse reactions to Tamoxifen are usually relatively mild and most frequently include hot flashes. However, more serious side effects can occur. Tamoxifen has been found to increase the risk of endometrial cancer and thromboembolic disease, such as pulmonary embolism (blood clot in the lung), and should only be used by patients with certain types of cancer or who are at high risk for developing breast cancer. Tamoxifen has also been shown to cause visual disturbances (e.g. cataracts) in a small percentage of women taking the drug. Other side effects may also occur. If you are taking Tamoxifen, your doctor should carefully monitor your progress to make sure that you are not experiencing any unwanted effects from the medicine.
Tamoxifen is a chemotherapeutic agent (a drug used to treat cancer because it can alter the growth of cancer cells). It is indicated to reduce the incidence of breast cancer in women at high risk for breast cancer. The recommended dose for this indication is 20 mg of Tamoxifen daily for 5 years. Not all women should receive Tamoxifen for the prevention of breast cancer. The decision to use Tamoxifen in a healthy woman for prevention reasons should be made in close consult with a knowledgeable physician who knows the patient’s medical history.
Many cases of breast and uterine cancer have been found to be estrogen receptor positive, an indication that estrogen may have stimulated or maintained tumor growth. Fortunately, cancer growth in these types of cancers can be halted by a number of agents, such as Femara (letrozole). Letrozole is in a class of drugs called aromatase inhibitors, which block the effects of estrogens by inhibiting the conversion of androgens to estrogen. Cytadren (aminoglutethimide), Arimidex (anastrozole), and Aromasin (exemestane) are other aromatase inhibitors in current use. Letrozole is indicated primarily for post-menopausal women with metastatic breast cancer (cancer that has spread beyond the breast) as first line therapy or as secondary therapy in patients with inadequate response to Tamoxifen or other anti-estrogens. Letrozole may offer an advantage over other aromatase inhibitors in clinical use as a result of greater potency and selectivity, decreasing the need for cortisol or aldosterone replacement. Side effects are generally mild and include headache. Women who are pregnant or who may become pregnant should not take letrozole.
Inositol hexaphosphate (IP6) is a substance that is found in beans, brown rice, corn, sesame seeds, wheat bran, and other foods that are high in fiber. It can also be purchased as a supplement at health food stores. Its proposed mechanism for fighting cancer is unknown, however, it is speculated that IP6’s effects are due to suppression of cancer genes or increased suppression of tumor growth – maybe both – without effects on normal cells. Animal studies have shown that IP6 may be effective in reducing tumor growth rates in several types of cancer, one of them being breast cancer. Few, if any, studies of IP6 have been performed in humans specifically on breast cancer or any other cancer for that matter. Research with IP6 is ongoing and may lead to a better understanding of treatment of various cancers. Be sure to talk with your physician before using any herbal or dietary supplements.
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Last Reviewed: Aug 15, 2002
Assistant Professor of Pharmacy Practice
Drug and Poison Information Center
Adjunct Assistant Professor of Pharmacy Practice
Drug and Poison Information Center