breast cancer
&
DESIGNER
estrogens

by Deepa Arora
Illustration by Malcolm Garris/PhotoDisc
June 25, 1998

Breast cancer has been in the news a lot lately. Studies that suggested breast cancer could be prevented gave women across the world a reason for hope against a disease that silently attacks 190,000 women every year.

But what do these studies mean for the average woman on the street? After the dust has settled and the publicity died down, questions persist.

Designer estrogens

Experts said studies suggesting that tamoxifen and raloxifene reduce the risk of breast cancer in women considered at high risk for the disease herald a new era of cancer prevention, as opposed to traditional cancer detection and treatment.

Tamoxifen and raloxifene are part of a class of drugs called SERMS (selective estrogen receptor modulators), sometimes called designer estrogens. They block the action of the female hormone estrogen that is known to encourage the growth of breast tumors.

Recent research suggests that tamoxifen (Nolvadex), used to treat breast cancer for many years, may lower the risk of developing breast cancer in women with certain risk factors. The tamoxifen study showed a 45 percent reduction in breast cancer cases -- it prevented the recurrence of the original cancer and the development of new cancers in the opposite breast.

The study was conducted in centers across the United States and Canada and funded by the National Cancer Institute. The 13,000 women who participated received either tamoxifen or a placebo. Designed as a "double-blind" study, in which neither the participant nor her physician knew which pill she was receiving, the trial allowed researchers to see the benefits and side effects of tamoxifen.

For instance, while tamoxifen acts against the effects of estrogen in breast tissue, it acts like estrogen in other parts of the body. So women who take tamoxifen may get some of the beneficial effects of menopausal estrogen replacement therapy, such as a lowering of blood cholesterol and a slowing of bone loss (osteoporosis). The most serious side effects of tamoxifen are an increased risk of uterine cancer and pulmonary embolism (blood clots in the lungs) and deep vein thrombosis (clots in major veins).

The study on raloxifene (Evista) showed that it reduced the incidence of breast cancer by about half. However, the good news about its effect on breast cancer came out of a study originally designed to test the drug's effect on osteoporosis. The trials lasted only two years. The short time fame and lack of follow-up on possible side effects leave experts cautious about making blanket recommendations.

"Tamoxifen and raloxifene are not for everyone. They are not a vaccine," said Aman Buzdar, MD, professor of medicine at the University of Texas M.D. Anderson Cancer Center in Houston. "Taking the drugs is a decision that every woman and her doctor need to make individually. My message to women is that there is an option out there, but it is not a casual decision to make."

Caution about tamoxifen stems from its known side effects. And caution about raloxifene stems from ignorance about consequences of long-term use. "The finding was secondary," said Buzdar. "The raloxifene studies did not last as long as the tamoxifen study. No drug is without side effects; it took 10 years to discover that tamoxifen can cause uterine cancer."

Victim of good news

Healthcare professionals say the recommended regimen of annual mammograms and breast self-exams is critical and should not be abandoned in the wake of these new discoveries. "Should all women start taking it? No," said Harmon Eyre, MD, executive vice president for research and medical affairs at the American Cancer Society. "The drugs reduce the risk of getting breast cancer, but do not eliminate it. Taking them should not replace a healthy lifestyle or early detection."

In addition, the Food and Drug Administration has not yet approved either drug for its preventive use in breast cancer. The process is expected to take until the end of 1998.

Looking forward

The National Cancer Institute is working to develop clear guidelines that physicians can use to help patients assess their risk factors. "The women [in the tamoxifen study] were generally at greater risk of developing breast cancer," said Lynn Hartmann, MD, an oncologist at the Mayo Clinic in Minneapolis.

Therefore, they were not representative of women in the general population.

Experts stress the need to address the long-range question. A head-to-head study of tamoxifen and raloxifene is expected to start this fall under the guidance of the National Cancer Institute. The study will last five years and look at 22,000 women randomly divided between tamoxifen and raloxifene. Comparison of the effectiveness and risks of the two medications will settle some of the doubts.

In addition, it will be immensely beneficial to the many baby boomer women entering menopause. Some cancer experts doubt researchers will be able to enroll women to take both tamoxifen and raloxifene. "A head-to-head study is important, but it will be difficult," said John Link, MD, an oncologist at Memorial Care Breast Center in Fountain Valley, California.

The media exposure and publicity surrounding raloxifene, and its probable lack of side effects, may make many women unwilling to take tamoxifen, he said.

None of these doubts, researchers say, can take away from the fact that this is the first time any drug has been shown to prevent cancer."It's a new era in cancer prevention," says Joanne Mortimer, MD, associate professor of medicine and medical oncology at the Washington University School of Medicine in St. Louis. "They may not be perfect drugs, but neither was the polio vaccine."

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RISK FACTORS

Hormonal factors Age at first menstruation, number of pregnancies, and late age at first live birth all may increase a woman's risk of breast cancer by affecting her lifetime exposure to hormones. Some scientists postulate hormones may promote cell division in breast tissue and increase the risk of mutations.

Hereditary factors Number of first-degree relatives (mother, daughters, or sisters) who have been diagnosed with breast cancer.

History of benign breast disease
The number of times a woman has had breast lumps biopsied.

A diagnosis of noninvasive breast cancer (lobular carcinoma in situ), a condition that greatly increases chances of developing invasive breast cancer.

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SCREENING GUIDELINES

The American Cancer Society's recommendations for detection in asymptomatic women are:

Age 20-39
Monthly breast self-examination and a clinical breast examination every three years.

Age 40+
Monthly breast self-examination, annual clinical breast examination, and annual mammogram.
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