Breast Cancer

As the editor of Mother Jones magazine, and the author of the breast cancer article in Mother Jones that your media critic, David Shaw, criticized on Sept. 13, we would like to correct a few of his misconceptions.

Shaw contends that there is no breast cancer epidemic. His subhead announces that “the facts suggest that early diagnosis and a larger population are behind the increase.” Such a statement demonstrates that Shaw has only a slight acquaintance with the research on breast cancer.

The larger-population argument is ridiculous. Disease statistics are always expressed in terms of cases (or deaths) per 100,000 population, specifically to prevent population growth from distorting the numbers. The breast cancer rate has increased approximately 26% since 1973.

As for the impact of early detection, the largest and most methodologically rigorous study contradicts Shaw. That study, by Emily White Ph.D., concluded that mammography explained most of the observed increase in breast cancer for women over 45, but only half the increase in younger women.

Why the increase in the breast cancer rate? There is no smoking gun. But a thorough reading of the epidemiological literature turns up a possibility that looks at least like a loaded gun--pollution by things like dioxin and organochlorine pesticides that have effects similar to estrogen, a hormone well-known to stimulate the growth of breast tumors.

Shaw is quick to cite one study, released last spring, showing no association between pesticide exposure and breast cancer risk. But the co-authors of that study point out several reasons why dismissing a link is premature. One is that compared with earlier studies, which did suggest a link, theirs included an unusually large proportion of Asian women, who are known to have a relatively low breast cancer risk. Remove the Asian women from the subject pool, and the data shows an association between pesticide exposure and breast cancer risk.

Furthermore, Shaw neglected to mention another study released around the same time that showed a clear association between breast cancer risk and the distance women live from chemical plants on Long Island.

The message of the Mother Jones article was that a potentially productive line of research has, to date, been given short shrift. As a magazine that goes out to activists, Mother Jones often alerts opinion leaders to issues that the mainstream media have either ignored, or in the case of Shaw’s article, trivialized.

JEFFREY KLEIN

MICHAEL CASTLEMAN

San Francisco