HEALTH

An ounce of prevention

Experts lead a new assault on breast cancer

PATRICIA CHISHOLM March 30 1992
HEALTH

An ounce of prevention

Experts lead a new assault on breast cancer

PATRICIA CHISHOLM March 30 1992

An ounce of prevention

HEALTH

Experts lead a new assault on breast cancer

Just before Christmas, 1990, Joanne Vozniak found a lump in her breast. But Vozniak was not overly concerned: her doctors in Red Deer, Alta., told her that it was probably a benign cyst, and she already knew that she was at low risk for breast cancer because of her age, 36, and the fact that she had nursed three children. But the lump grew

and, in January, a biopsy revealed a malignant tumor. Quickly, she underwent a mastectomy and a tubal ligation to prevent further pregnancies. And although she endured nauseating chemotherapy treatments, one specialist told her that the disease probably would return within a year. In accordance with widely accepted medical recommendations, she has made adjustments to her daily habits, including examining herself regularly and switching to a low-fat diet. Although it has been 14 months since the onset, she has not suffered a recurrence. But Vozniak, who lives with her geologist husband, Charlie, and three children, says that she takes nothing for granted. While she tries not to worry about the disease coming back, she acknowledges that life has taken on a different perspective, a sense that survival is something to be fought for. “Old age seems like a victory to me now,” she says.

Like Vozniak, a growing number of women

say that prevention and early detection are their best hopes against a disease that kills one in 25 Canadian women. Many doctors agree, concluding after years of research that breast cancer is at least partly caused by environmental factors, such as diet, that can be controlled. They also point to new studies that promise to offer alternatives to women looking for ways to

prevent the onset or recurrence of the disease. In April, the U.S. National Cancer Center will announce plans to launch a massive study of the cancer drug tamoxifen. At least two Canadian studies are investigating the positive effects of a low-fat diet on breast cancer. And in six months, University of Toronto doctor Anthony Miller will release the results of an 11-yearlong inquiry into the effectiveness of breast screening by mammography and physical examination by a health professional. Said Richard Margolese, a surgeon who specializes in breast cancer at the Jewish General Hospital in Montreal: “There are no guarantees, but you can shift the odds. It’s like wearing a seat belt or not smoking—you can take some measures to help protect yourself.”

Still, the numbers are not encouraging. The Canadian Cancer Society says that one in 10 Canadian women is likely to get breast cancer. In the United States, the number is now one in

nine. In both countries, the death rate among those who get the disease is about one in four, over a five-year period. This year, an estimated 5,200 women in Canada will die of the disease. While death rates among breast cancer patients are now lower than 20 years ago, the number of women diagnosed with the disease is higher, and many women and their doctors say that two decades of research should have yielded better results. Most experts respond that the high number of new cases is partly explained by the increasing age of the population and by improvements in the quality and extent of mammographie testing. The test, which uses small doses of radiation to highlight changes in breast tissue, can isolate tumors too small to be detected by physical examination. As a result, experts say, the figures now include cancers that would not have been found two decades ago.

Doctors acknowledge, however, that better detection is only part of the explanation and that other factors need much more research. Dr. Maureen Henderson, an epidemiologist at the Fred Hutchinson Cancer Research Center in Seattle, has conducted preliminary studies on the relationship between dietary fat and breast cancer in post-menopausal American women. Like many researchers, she believes that future studies will confirm a direct link between the high-fat diet of North Americans and the relatively high rates of breast cancer in the United States and Canada. International studies have already shown g that Japanese women, whose £ diet contains about 23 per I cent fat, have a far lower

< incidence of breast cancer I than North American wom-

< en, whose typical diet includes about 42 per cent fat. However, within a genera-

tion of moving to North America, Japanese women show the same rate of breast cancer as other North American women.

Diet research is also under way in Canada, at the Ontario Cancer Institute in Toronto and the British Columbia Cancer Agency in Vancouver. Those studies are examining the relationship between a low-fat diet and the prevention of breast cancer in healthy women. Gregory Hislop, an epidemiologist working on the Vancouver study, echoed Henderson’s conclusions and added that only a dramatic drop in dietary fat is likely to have a preventive effect on breast cancer. “It is still very controversial, but most people agree that it is prudent to reduce fat intake,” Hislop said. “But it can be difficult to get it very low, say 20 per cent, without the advice of a dietitian.”

In addition to dietary changes, researchers are exploring new ways to use the hormonal drug tamoxifen. A staple of breast cancer

treatment for more than 10 years, tamoxifen has been given mainly to women who have already undergone surgery for breast cancer. Although the process is not completely understood, scientists say that estrogen, a female hormone, plays a vital part in stimulating the growth of certain lands of breast cancer cells. Tamoxifen apparently helps by reducing the stimulative effects of estrogen. Researchers are trying to determine if the drug will be useful in fighting all women’s cancers.

Now, tamoxifen is to be tested as a method of preventing breast cancer in healthy women who may be at higher risk of contracting the disease because of their family history. The $68-million study by the U.S. National Cancer Institute will likely involve more than 16,000 women. At least 12 Canadian centres will participate, including Jewish General in Montreal, Women’s College Hospital in Toronto, the Hamilton Regional Health Centre and the B.C. Cancer Centre in Vancouver. Said Michael Poliak, an associate professor of medicine at McGill University in Montreal: “Every time we have checked out this drug so far, we have discovered good things about it. But it has never been used for prevention on a wide scale. This will be one of the largest clinical trials ever undertaken in the history of medicine.”

Scientists also say that another drug, taxol, has shown potential as a new kind of chemotherapy since its first clinical trials in the late 1960s. It has been an effective treatment of ovarian cancer, and researchers are optimistic

about its application for breast cancer, but its use has so far been limited because it has been difficult to obtain. Taxol occurs naturally in the bark of the rare Pacific yew tree, but the U.S. National Cancer Institute revealed last week that researchers at Stanford University in Cali-

fornia may have found a way to synthesize the drug. Still, a spokesman for the institute cautioned that taxol will remain in short supply for at least a few more years.

At the same time, less well-developed but potentially powerful genetic research is closing in on defective genes that may predispose some women to breast cancer. When researchers are able to pinpoint such a link, women who carry the defective genes may be identified and treated with preventive drugs, such as tamoxifen. Among the most promising advances so far is research by U.S. scientists who in 1991 identified the chromosome that most probably carries a gene linked to the development of breast cancer. But the task is a huge one, and scientists warn that breakg throughs with practical applications I are still years away. Said Irene Andruï lis, a senior scientist at Mount Sinai o Hospital in Toronto: “Finding a genetic link to breast cancer is akin to finding a house on a map of the world—so far, our discoveries have only told us which city to look in.”

With answers still to come in many areas of research, patients like Joanne Vozniak will continue to place their hopes in things that they can do for themselves.

PATRICIA CHISHOLM