Marin Independent Journal
11/20/09
Breast cancer researchers at Sausalito forum defend mammogram advice
Breast cancer researchers and community activists who gathered at a Marin forum this week defended the federal government's new recommendation on mammograms and discussed cutting-edge research results.
The event's headliner, Dr. Linda Birnbaum, director of the National Institute of Environmental Health Services, said the recommendation - that women start breast cancer screening at age 50 instead of 40 - was developed by a team of experts who reviewed "all the information about the number of mammograms that were done, and the number of cancers that were detected, and biopsies that were conducted, and some of the impacts of repeated radiation on women.
"Their conclusion is that scientific study didn't support the general use of mammograms for everyone the way it had," Birnbaum told an audience of more than 200 people who gathered Wednesday at Cavallo Point Lodge in Sausalito.
The forum was held in conjunction with a conference of scientists who are studying the effects of environmental factors - such as chemical exposure, diet and exercise - on breast cancer risk.
Dr. Robert Hiatt, a University of California at San Francisco professor who heads the Bay Area Breast Cancer and Environment Research Center, said, "They're finding that there are many more negative consequences of false positive examinations than were anticipated. The only hard evidence we have is randomized trials that show a reduction in mortality for women over 50."
Both Birnbaum and Hiatt said the decision whether to have a mammogram is one that each woman needs to make with her doctor.
"Women who have risk factors will continue to have mammograms more frequently, as they have in the past," Birnbaum said.
Jeanne Rizzo, who heads the Breast Cancer Fund, a San Francisco-based nonprofit that advocates the elimination of environmental and other preventable causes of breast cancer, also supported the recommendation. Rizzo said that mammograms are an outdated, ineffective mode of screening that expose women to radiation, a known carcinogen.
"We haven't invested in an alternative, non-invasive form of screening," Rizzo said. "I would hope we would mobilize to that action going forward."
Birnbaum said a promising new study being conducted by the institute she heads involves the close monitoring of 51,000 women whose sisters developed breast cancer. Researchers are tracking the participants' lifestyle choices, diet and environmental exposures. Samples of women's blood and urine are taken regularly.
Even though recruitment for the study was completed only a couple of months ago, Birnbaum said some data are already coming in.
"We're finding, for example, that women who are obese have shorter telomeres," Birnbaum said.
Telomeres are a DNA sequence that appears at the end of each chromosome, a bit like the plastic tips at the ends of shoelaces. Normally, a person's telomeres shorten as they age, and the frequency of all kinds of cancer increases with age.
Birnbaum said preliminary results also indicate that higher stress levels lead to shorter telomeres.
"But the good news," she added, is that we're finding that multivitamins appear to lead to longer telomeres."
Hiatt said it is difficult to research environmental effects using women who have already developed breast cancer.
"When you realize that breast cancer takes 20 to 30 years to develop, and you're studying adult women trying to assess their exposures 20 to 30 years before, where there is no objective marker for it, you can understand the difficulty," Hiatt said.
The research center that Hiatt oversees, one of four such centers in the country, is conducting a study of 400 pre-pubescent girls ages 6 to 7. The study is looking at chemicals known as endocrine disrupters, which influence estrogen production. It is thought that these chemicals, found in some plastics and cosmetics, could be responsible for the earlier onset of puberty seen in some girls.
Studies have shown that use of estrogen and progesterone to treat menopausal symptoms can increase breast cancer risk. Medical researchers now suspect that use of hormone replacement therapy was responsible for an alarming spike in Marin breast cancer cases during the 1990s. After the link between hormone therapy and breast cancer was established in 2002, many Marin women stopped using the therapy and the incident rate diminished. But Marin's rate remains relatively high.
From 2003 to 2007, the most recent years for which data are available, the rate of breast cancer in Marin averaged 150.9 cases per 100,000 women per year among non-Hispanic white women. That compared with rates of 141.7 cases for the same group of women throughout the Bay Area and 137.9 cases across California. From 2002 to 2006, the rate of breast cancer throughout the United States was 134 cases per 100,000 women per year among non-Hispanic, white women.
But Birnbaum said, "Just like cancer is not one disease, breast cancer is not one disease. It is actually many different diseases, which are all going to have different genetic and environmental causes."
Hiatt said using biomarkers "you can distinguish at least five different kinds of breast cancer." The growth of three of the most common types is accelerated by estrogen, progesterone and a protein called human epidermal growth factor receptor-2.
But a far less common type is known as triple-negative breast cancer, because it lacks receptors for any of these three substances. Hiatt said this more aggressive cancer seems to occur more commonly in younger women and women who are black.
