Mammography - The Hidden Downside, Part IV
Cornelia J. Baines, MD, of the University of Toronto, deputy director of the prestigious Canadian National Breast Screening Study, has written several papers that are critical of screening mammography. She writes: “An unacknowledged harm [of screening mammography, ed.] is that for up to 11 years after the initiation of breast cancer screening in women aged 40-49 years, screened women face a higher death rate from breast cancer than unscreened control women, although that is contrary to what one would expect” (Baines 2003).
How could this happen? How can it be that instead of saving their lives, earlier detection might actually result in a greater likelihood of death in these women?
It is a phenomenon well known to researchers that the removal of the primary tumor can trigger the sudden growth of tiny clusters of cancer cells (called ‘micrometastases’) that have until that point lain dormant in distant sites. Researchers have shown that the primary tumor inhibits the ability of these subsidiary distant deposits to grow, perhaps by releasing powerful biologically active substances, such as angiostatin and endostatin, which prevent tumors from stimulating the development of their own blood supply (a process known as angiogenesis).
Without the ability to generate a new and adequate blood supply, tumors, even tiny, clinically invisible tumors, cannot grow, and while the primary tumor is still in place, and still secreting these angiogenesis-suppressing substances, the micrometastases remain dormant. But once the primary tumor - the ‘conductor of the cancer orchestra,’ so to speak - has been removed, the restraints on growth are removed and the microscopic malignant deposits in distant sites suddenly acquire the power to induce their own blood supply and grow independently.
Much of the pioneering work on the role of angiogenesis in tumor growth was done by Judah Folkman, MD, of Harvard University, winner of the American Society of Clinical Oncology’s (ASCO) highest honor, the Karnofsky Award (1996). Working alongside Prof. Folkman, Dr. Michael Retsky and other researchers have studied the question of the mammography paradox and have suggested that not only is the removal of the primary tumor the spur to proliferation of dormant metastases, but also that surgery itself, by creating a physical wound, independently triggers the release of growth factors that, in addition to assisting healing of the surgical wound, also promote tumor growth. This effect is particularly marked in younger women with node-positive disease.
The fact that the mammography paradox is confined to younger (as opposed to older) women undergoing mammography is a reflection of the biological differences between pre- and postmenopausal women, Dr. Retsky and his colleagues suggest. In premenopausal women, the hormonal environment may encourage the estrogen-driven proliferation of breast cancer cells, putting younger women at an extra disadvantage in terms of their susceptibility to aggressive metastatic cancer growth.
In a 2001 paper on the subject of the mammography paradox, published in the journal Breast Cancer Research and Treatment, Dr. Retsky and colleagues state that “Each woman should be informed of the risks and benefits [of mammography] and decide for herself whether to undergo screening mammography. Young women are, however, not routinely warned that screening and resection may accelerate breast cancer mortality” (Retsky 2001).
This sentiment is echoed by the University of Toronto’s Dr. Baines, who asks, “Shouldn’t women aged 40-49 years know that, 3 years after screening starts, their chance of death from breast cancer is more than double that for unscreened control women? Shouldn’t they be informed that it will take 16 years after they start screening to reduce their chance of death from breast cancer by a mere 9 percent?”
Dr. Baines, the author of 70 PubMed-listed scientific articles, also points out that there is an almost willful silence both within and outside the medical profession on the subject of the dangers and ineffectiveness of screening mammography. Although the mammography paradox was originally identified in an article published in 1997 in the Journal of the National Cancer Institute, this important news was cited only 8 times in the ensuing 6 years - and four of these citations were by the same group of researchers (Cox 1997).
Contrast this peculiar absence of debate with the deafening clamor from all sides in favor of mammography screening - and with the mounting chorus in support of the recommendation that women should begin annual mammography at the age of 40 - the very group of women most likely to be harmed, rather than helped, by mammography.
It is often fear that drives women to seek screening mammography, a fear that is fostered, actively and tacitly, by a medical profession (and a highly profitable screening industry) that is doing little to inform women of their real risks, nor what gain, if any, they can really expect from mammography.
The risk of developing breast cancer is 11 percent (1 in 9) over a woman’s lifetime. While women tend to believe that almost 40 percent of all deaths among women are due to breast cancer, in reality the actual percentage is 4 percent. In a survey of 1000 American women, 71 percent expressed the belief that screening reduces breast cancer deaths by 50 to 100 percent (Domenighetti 2003).
Meanwhile, several rigorous clinical trials have shown that mammography not only does not confer a clear survival benefit, but may in fact have the opposite effect, contributing to an increased, rather than a reduced risk of dying in premenopausal women. Despite these stark facts, raising questions about the value of mammography has come to be seen as “un-American,” one epidemiologist reportedly remarked (Baines 2005).
As journalist and medical writer Gina Maranto pointed out succinctly in a Scientific American article on the subject:
“Physicians, radiologists, statisticians and public health officials have made claims and counterclaims and with sometimes startling emotion have accused one another of misreading or misrepresenting data, of performing faulty analysis and of perpetuating myths that have dire consequences for women. Some specialists, as well as cancer societies, women’s health advocates and manufacturers of mammography machines, have argued that mass screening saves lives; others on the clinical front lines and in policy-setting roles have contended that evidence from a number of randomized controlled trials does not support such a claim” (Maranto 1996).
The National Institutes of Health, the National Cancer Institute and most of the other public agencies charged with formulating recommendations for screening based on scientific evidence routinely go out of their way to discredit studies that cast doubt on the usefulness of mass mammography screening. Mammography is a cornerstone of the American ‘war on cancer.’ That these national policy makers cannot even bring themselves to publicly acknowledge misgivings about the procedure, much less to re-examine their recommendations in the light of the alarming truth about the mammography paradox is little short of staggering.
- Ralph W. Moss, Ph.D.
