Fw: Against cancer, don't wait for 100% proof

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----- Original Message ----- From: Kathi

Sent: Thursday, September 19, 2002 11:44 AM

Subject: Against cancer, don’t wait for 100% proof

http://www.abs-cbnnews.com/abs_news_body.asp?section=Opinion & OID=3302 Against cancer, don’t wait for 100% proof By BARRON H. LERNER Special to Newsday Lerner, M.D., is author of The Breast Cancer Wars and teaches medical history at Columbia University. When women with silicone breast implants were told in 1995 that there was no scientific proof that their implants caused their fatigue, headaches and swollen joints, they were furious. “We are the proof!” they screamed. A nearly identical sense of frustration arose with the recent announcement that an $8-million National Cancer Institute study had found no connection between the incidence of breast cancer and a variety of pollutants found in food, air, soil and water on New York’s Long Island. As interested parties debate future strategies for studying high breast cancer rates, it is a good time to reflect on the nature of scientific proof. How should we respond when studies generate unexpected or undesirable results? At what point, if any, should a worthy political agenda, such as finding the causes of breast cancer, be abandoned for lack of scientific evidence? Science has long been able to demonstrate connections between certain environmental toxins and cancers. In 1775, for example, London physician Percival Pott demonstrated that the occupational exposures of chimney sweeps caused high rates of scrotal cancer. Epidemiological studies published in the 1950s proved the causal relationship between cigarette smoking and lung cancer. Asbestos has been shown to cause a rare cancer of the lining of the lungs. But studies seeking to identify carcinogenic substances are notoriously hard to carry out. In contrast to randomized controlled trials, which compare the health outcomes of individuals undergoing a specific medical intervention and a control group, studies of environmental toxins must identify a group of cancer patients and then accumulate evidence about possible hazardous exposures, many of which likely occurred 10 to 20 years earlier. Such data collection is tedious and susceptible to false recollections. Even in the case of cigarettes and lung cancer, where there is a very strong association, it took decades to prove the connection. When breast cancer activists persuaded Congress in 1993 to earmark funding for a study of environmental toxins on Long Island, they were well aware of the potential pitfalls of this type of research. Yet one of the hallmarks of activism for breast cancer, as well as for aids and other diseases, has been to push for scientific data that can either prove or disprove long-held claims. For example, it was good scientific studies of breast cancer surgery in the 1970s that finally led to the abandonment of the radical mastectomy, a highly disfiguring operation. Thus it seemed prudent to ascertain, once and for all, if high rates of breast cancer stemmed from exposure to toxic waste and other pollutants. One point of controversy that emerged as the Long Island study began was which potential carcinogens would be investigated. The activists hoped that the focus would be on a series of chemicals currently being used in insecticides, plastics, cosmetics and other consumer products. But the researchers chose to study different chemicals that were easier to measure in the blood and body fat: the insecticides DDT, diedrin and chlordane; the insulating compounds known as PCBs; and polycyclic aromatic hydrocarbons (PAHs), which result from the burning of fuel, garbage and charbroiled meat. Except for a chance association between PAHs and breast cancer, the study found no connections. How can these findings be explained? First, the study, like other recent research that has generated similar findings, may be correct: a link between pollution and breast cancer, however appealing, may not exist. Alternatively, there may be such a connection, but due to limitations in scientific technique, it cannot be proved. Similar issues arose in the case of silicone implants, in which multiple studies found no association between the implants and women’s symptoms. Likewise, the limits of scientific evidence have been revealed in debates over screening mammography. Although there have been eight randomized controlled trials of mammograms, statisticians cannot agree whether use of breast X-rays prevents deaths from breast cancer. At what point, if any, do further scientific studies of these issues make no sense? The difficulties in obtaining accurate scientific information even extend to the quantification of how much breast cancer truly exists. As reported in Newsday, the New York State Department of Health has used insufficient statistical tools to evaluate the actual severity of the Long Island cancer clusters that sparked the breast cancer study. Where do we go from here? Some Long Island activists are insisting on more, and better, scientific studies of the environmental connection to breast cancer. To be sure, we should welcome research that, using advances in computer technology and in our understanding of breast cancer biology, may overcome the methodological problems of past studies. But at some point activists and researchers should acknowledge that a link between breast cancer and environmental toxins, if it exists, may be impossible to prove. Does this mean the quest to rid Long Island and other areas of toxic waste and pollutants should be abandoned? Absolutely not. Indeed,four of the five substances in the Long Island study -- DDT, chlordane, dieldrin and PCBs -- already are banned. Rather, we can push aggressively for laws that eliminate or regulate other potential carcinogens, notwithstanding the lack of conclusive studies. Breast cancer activists have an admirable track record of promoting good science, but definitive scientific proof should not be a prerequisite to good policy. Please send your comments or feedback to newsfeedback@...