While medicine has done much to ease human suffering, public health has done more to prevent it. The health gains from public health measures such as better nutrition, clean drinking water and safer workplaces far outstrip the gains from medicine.¹

Public health policy accepts small risks, such as those incurred by vaccination or seat belts in cars, for large benefits. "Chemoprevention" experiments, which test potent drugs to prevent disease, introduce a troubling new standard: large risks are justified by small or ambiguous benefits. Canadian women are involved in these experiments, which blur the boundary between disease prevention, where safety is paramount, and disease treatment, where risks to the sick are weighed against potential improvements in their condition. The strategy of prescribing drugs to healthy people now threatens to overtake, and even displace, the traditional public health strategy of identifying and removing or reducing the causes of disease. At the same time, Canadian safety standards for medications, medical devices and environmental contaminants are quietly eroding.

Breast Cancer and Chemoprevention
Over the past decade, breast cancer has dominated the chemoprevention debate. In April 1998, front-page headlines described a breakthrough in preventing breast cancer: "We know for the first time in history that we can prevent cancer through pharmaceuticals," said one of the researchers in the Breast Cancer Prevention Trial (BCPT), an experiment involving 13,388 Canadian and American women.² Six months later, the U. S. Food and Drug Administration (FDA) approved the use of tamoxifen — previously approved only to treat breast cancer — for women "at high risk" of developing the disease.³ Health Canada has not approved tamoxifen (an estrogen antagonist) for breast cancer risk reduction, which means pharmaceutical companies cannot promote the drug for that purpose in Canada. However, Canadian physicians can prescribe the drug to healthy women at their own discretion, a practice known as "off-label" use.

In the BCPT, tamoxifen lowered the risk of breast cancer but raised the risks of endometrial cancer, blood clots and vision problems, prompting one physi-cian to observe that "disease prevention" had been replaced by "disease substitution."⁴ Three women in the tamoxifen arm of the trial died from blood clots in their lungs.

Healthy Canadian and American women were then recruited to the Study of Tamoxifen Against Raloxifene (STAR), a follow-up to the BCPT that compared tamoxifen to a similar drug, raloxifene. Raloxifene also causes blood clotting. (All women in the STAR trial are exposed to one drug or the other.) Women's health groups critiqued the breast cancer chemoprevention trials as the latest in a series of risky drugs and medical products marketed for use in women without adequate scientific rationale or testing. Nor is breast cancer the only disease for which treatment drugs are tested for prevention. Others include heart disease, thinning bones, prostate cancer and schizophrenia.

The Precautionary Principle vs. Risk Management
Women's health groups, public health researchers, ethicists, environmentalists and many health practitioners have stressed the need to adopt a public health approach to breast cancer prevention. They promote the Precautionary Principle, a safety-first premise that states that when there are reasonable scientific grounds for believing a process or product may not be safe, even when cause and effect relationships are not fully understood, preventive action must be taken. If Health Canada made the Precautionary Principle its standard for health protection in regulating food, drugs and medical devices, and in protecting the environment, the prevention of disease would be maximized without recourse to drugs. This would also protect the public from the testing and marketing of chemoprevention drugs that introduce new threats to health. However, in the revised Canadian Environmental Protection Act (1999), the government diluted the initially strong statement of the Precautionary Principle after industry interventions led to last-minute amendments.⁵

Combatting the Drift to Chemoprevention
For a decade the chemoprevention debate has incited FDA hearings in the United States, media coverage and meetings of community groups. Although hundreds of Canadian women have been recruited to the BCPT and STAR trials, Canada's health protection agency has yet to provide a policy forum to which women could bring their concerns. The renewal of Canada's health protection system, now under way, must address the public health implications of chemoprevention. Policy changes are needed at the highest level to affirm the Precautionary Principle as the basis for health protection and to confine chemoprevention to situations where it can be used ethically, safely and economically. To achieve this goal, Women and Health Protection recommends that:

The regulation of drugs, food, radiation equipment and the Canadian environment should all occur through a system that is independent from industry.

The Canadian government provide venues for public input at all stages of chemoprevention drug testing and approvals, and post transcripts of these meetings on the internet to ensure public access to the information.

A regulatory office be created to oversee clinical trials in Canada, including chemoprevention trials, in consultation with relevant professionals and public interest health groups.

Health Canada be mandated to intervene at regulatory hearings in the United States and other countries carrying out clinical trials that involve Canadian participants to demand that the safety of Canadian participants be protected.

Women and Health Protection is supported financially by the Women's Health Bureau of Health Canada. The views expressed in this article do not necessarily represent the official policy of Health Canada. To obtain a copy of the complete 2001 paper (of which this is a part), go to the website of the Centers for Excellence in Women's Health at www.cewh-cesf.ca/bulletin/ v2n2/page5. html.

Notes

1. Centers for Disease Control. Ten great public health achievements—United States, 1900-1999. Morbidity and Mortality Weekly Report, April 2 1999; 48(12): 241.
2. Dr. Richard Margolese quoted by Semenak S. 'Breast cancer treatment hailed'. The Montreal Gazette 1998 April 6; A1.
3. Letter to Zeneca Pharmaceuticals from Robert Temple, M.D., Director, Office of Drug Evaluation, Center for Drug Evaluation and Research, FDA. ww.fda.gov/cder/foi/ appletter/1998/ 17970s40.pdf
4. Fugh Berman A, Tamoxifen in healthy women: Preventive health or preventing health? National Women's Health Network News 1991; September/October: 3.
5. VanderZwaag D. The precautionary principle in environmental law and policy: Elusive rhetoric and first embraces. Journal of Environmental Law and Practice 1999; 8:355-375.