Study of Breast Cancer Pill Raises Hopes and Concerns
Sunday, May 22, 2005
Neva Hart's mother, grandmother and aunt all battled breast cancer. So when Hart heard about an experiment testing a pill that might protect women like her from the malignancy, she jumped at the chance to volunteer.
"I wish science could find something aside from chopping off parts of the body to fight this disease," said Hart, 57, of Wirtz, Va. "I decided to donate my body so people might not have to go through that kind of torture."
The study that Hart joined and a similar one based in Europe are raising hopes that a new class of drugs may offer women at high risk of breast cancer a safe way to protect themselves. But the experiments also raise thorny questions about whether the potential benefits outweigh the possible risks.
"Studies like this raise serious ethical issues," said Michael A. Grodin, a bioethicist at the Boston University School of Public Health. "What you're comparing here is the risk of getting cancer, which is unknown, against the potential risk of side effects from the prevention, which also is unknown. You're not treating people who are sick. These are healthy women."
These kinds of questions are becoming increasingly common as researchers focus more and more on trying to prevent, rather than treat, disease -- often testing powerful drugs on people who have theoretical risks based on nebulous attributes such as age and family history rather than more concrete risk factors such as high cholesterol or high blood pressure.
"It's not like someone has the disease. In this case you're treating a statistic -- the chance of getting the disease," Grodin said. "If you knew this drug had no side effects, then it wouldn't be as concerning. But you don't know that."
Breast cancer is diagnosed in about 211,000 U.S. women each year, and about 40,000 die of the disease, making it the most common cancer and the second most deadly cancer, after lung cancer, among women.
Surgery, radiation, chemotherapy and estrogen-blocking drugs have cut the breast cancer death rate. But with the incidence still rising, researchers, patient advocates and women at risk for the disease desperately want ways to prevent the cancer in the first place. Last week, new research suggested that low-fat diets may minimize the likelihood that breast cancer will recur after treatment, a strategy also being tested to prevent first tumors. But that approach remains far from proven.
The study that Hart joined, dubbed the ExCel trial, is testing a drug known as exemestane, or Aromasin, one of a class of new drugs called aromatase inhibitors. Aromatase inhibitors block formation of estrogen, which can fuel the growth of breast cancer cells. The drugs have been shown to cut the relapse rate for breast cancer at least as effectively as the only other estrogen-blocking drug available, tamoxifen. Tamoxifen reduces the risk of breast cancer, but it also raises the risk of blood clots and uterine cancer, which has discouraged many women from taking it.
Seeking an alternative, researchers launched the ExCel trial and a similar study testing another aromatase inhibitor called anastrozole, or Arimidex, to see whether the drugs can prevent first cancers. Anastrozole is being tested in Europe, the Middle East and other parts of the world.
"There is abundant evidence that inhibiting estrogen can prevent new primary breast cancers. We estimate that we may be able to reduce the risk by 60 to 80 percent," said Paul Goss, director of breast cancer research at Massachusetts General Hospital in Boston, who is leading the ExCel study. "We're very optimistic."
Researchers have started recruiting what they hope will be about 4,500 postmenopausal women in the United States, Canada and Spain who are considered at high risk for breast cancer because of age, family history or other factors. For five years, half the women will take the drug while the other half take a placebo. The study is being sponsored by the Canadian Cancer Society, the National Cancer Institute of Canada and the drug's maker, Pfizer Inc.; the company is not directly involved in the study.