Go back to Front pageSAN FRANCISCO -- White women in the Bay Area have the highest rate of breast cancer in the world -- a rate half again as high as that for most European women and five times higher than for women in Japan, according to a report from an international cancer research agency.
The authors of the report could not pinpoint a cause of the high breast cancer rates, but said that several factors, including diet and exposure to toxic substances, might be to blame.
"There must be something about being in the United States and in the Bay Area that is associated with breast cancer," said Dr. Robert A. Hiatt, director of prevention science at the Northern California Cancer Center in Union City, a branch of the California Cancer Registry.
"Something is going on that has to do with the environment. It might be diet. It might be medication. It might be reproductive practice. But we don't know for sure."
Hiatt and others also suggested that the rate may be higher because of more effective screening here.
The report, entitled "Cancer in Five Continents," was prepared by the International Agency for Research on Cancer and released by the Northern California Cancer Center.
Agency researchers found that in the nine Bay Area counties, there will be about 4,500 new cases of breast cancer and 1,000 deaths this year -- or 12 new cases and three deaths every day, according to the cancer center.
The rates are highest for white women, followed by blacks. The lowest rates are among Latinas and Asian and Pacific Island Americans.
Studies show that breast cancer rates for migrants become more like the rates of women in their host countries than in their countries of origin, leading researchers to believe that environmental or behavioral patterns affect the onset of the disease.
Following the Bay Area on the international list are Hawaiian women living in Hawaii; whites in Atlanta; Bay Area blacks; women in British Columbia, Utah and Geneva, Switzerland; Atlanta blacks; women in Denmark; Jewish women in Israel; and women in New Zealand and Scotland.
While the Bay Area has the highest breast cancer rate in California, white women in Los Angeles and Orange County aren't far behind. The two regions aren't included in the worldwide ranking because their cancer registries don't go as far back as 1987, the year in which data were taken for the ranking.
The Northern California Cancer Center, in making the data public, said that "it is not clear why invasive breast cancer rates in the Bay Area are so high." But the authors suggest three possibilities, in order:
Scientists have known for years that the Bay Area ranks high for breast cancer among the areas that collect data. The Breast Cancer Fund, a nonprofit public interest foundation, took the information public at a recent press conference.
Andrea Martin, one the fund's founders, said she thinks the Bay Area leads the list for two reasons. First, women are taking charge of their health care and undergoing more breast exams, which turn up more cancers.
"But it also means," Martin said, "that as a more affluent community, we are able to avail ourselves of more products and foods that contain toxins."
Hiatt, who is also assistant director of the Division of Research at the Kaiser Foundation Research Institute in Oakland, agrees the Bay Area's rate is higher because of effective screening, including mammograms, clinical examinations and self-exams that detect the cancers early.
And that, Hiatt said, is a good thing. "If we're picking up cancers early," he said, "we would expect the mortality to go down soon." In the latest two years, data show a slight dip in the death rate.
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