The Mammography Paradox
hat mammography is not as effective in saving lives as its promoters have insistently claimed is bad enough, but more alarming by far is the little-publicized fact that in women aged 40-49, mammography is actually associated with an increased, rather than a decreased, risk of death- a phenomenon known to researchers as the “mammography paradox.”
Yes, you read that right: mammography in younger women (ages 40-49) may actually accelerate, rather than reduce, breast cancer mortality.
This increased death rate from breast cancer in younger women who undergo screening mammography has been documented consistently in screening trials across different countries, settings and populations. It is a fact known to many researchers in the field, yet it remains largely unknown to the general public – and it certainly not a danger of which women are routinely made aware by their healthcare providers.
ne critic of exclusive reliance on screening mammography is Cornelia J. Baines, MD., of the University of Toronto. Dr. Baines is hardly an outsider to the field. She is deputy director of the prestigious Canadian National Breast Screening Study, and the author of 70 PubMed-listed journal articles. She has also written an important paper that is frank in its discussion of this issue. In this paper, aptly titled “Mammography screening – Are women really giving informed consent?” Dr. Baines says: “Many women remain unaware of the extent to which efforts to achieve breast cancer control through mammography screening may be doing harm as well as good. An unacknowledged harm 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?
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?
t 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.
For a previous newsletter on the subject of Retsky’s work on the role of surgery in stimulating cancer growth, please click or go to:
http://www.cancerdecisions.com/073105.html
n 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.
t 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.
Over-diagnosis is an acknowledged problem with screening mammography, leading to treatment that for some people may be both unnecessary and intrinsically damaging in its own right. The danger of a false positive reading, with all the attendant anxiety and ensuing interventions, is also always a risk in current screening mammography programs. Similarly, the real possibility of a false negative – a clean bill of health that turns out to be illusory – is inherent in screening mammography. Moreover, there is no guarantee whatever that a breast cancer identified by screening mammography will be curable.
Furthermore, as we have seen, for some premenopausal women, particularly those with node-positive disease, there is the additional danger that early diagnosis by means of mammography may actually reduce survival rather than extend it. It is worth noting that mammography screening for premenopausal women is not recommended in any other country except the US.
For older (postmenopausal) women, the benefits of mammography may be marginally greater, at least over time, although here again, there is a danger of over-diagnosis, and of high false positive (and negative) results.
Meanwhile, the debate over screening mammography continues unabated. The US medical profession continues to stand unwaveringly behind its recommendation that women aged 40 and up should undergo annual mammography. Just last month, for example, the New England Journal of Medicine (NEJM) published a paper that made headlines all over the world. It claimed that mammography had been proven responsible for saving lives from breast cancer. It is therefore worth examining this report a bit more closely.
t should be borne in mind that this was not actually a new clinical trial. Instead, this study was based on what are called “computer modeling techniques” (i.e., statistical inferences and predictions based not on direct observations of patients but on computer simulations). These techniques were used to re-analyze seven prior studies of the effectiveness of mammography. In addition, no modifications or allowances were made in order to achieve consistency between the seven studies. Five out of the seven studies showed that mammography had contributed less to the decline in death rates than had improvements in treatment.
he most vocal proponents of screening mammography tend to claim that screening reduces the death rate by anywhere from 45 percent to 64 percent. However, in this study screening mammography was only found to have contributed approximately 15 percent to the decline in death rates from breast cancer, while improvements in treatment were found to have contributed approximately 19 percent (Berry 2005).
The usefulness of this study, and the validity of its conclusions, are further undermined by the fact that the sample population spanned the entire age range, from 30 to 79 years. No attempt was made to separate women into different age groups. As Professor Cornelia Baines of the University of Toronto pointed out, this is a particularly important omission since the natural history of the disease varies widely in different age groups. For women in the age group 30-49, mammography’s benefits are the most questionable of all – a fact that was entirely ignored by this study (Baines, personal communication).
Yet despite this latest favorable NEJM article and despite the incessant repetition of the “mammography saves lives” mantra, there is, astonishingly, still no consistent, substantial scientific evidence that regular mammography results in a significant reduction in mortality from breast cancer. In an important paper published in 2000 in the prestigious journal Lancet, Swedish researchers, working on behalf of the international Cochrane Review organization, reviewed the quality of the major mammography trials to date and came to the following conclusions:
“Screening for breast cancer with mammography is unjustified. If the trials are judged to be unbiased, the data show that for every 1000 women screened biennially throughout 12 years, one breast cancer death is avoided whereas the total number of deaths is increased by 6″ (Gotzsche 2000).
In a paper examining the contradictory evidence concerning mammography screening, Steven Goodman, MD, a biostatistician at the Johns Hopkins Sidney Kimmel Cancer Center, Baltimore, MD, has written:
“If we take a step back, this controversy looks almost Swiftian when we consider that even under the most optimistic assumptions, mammography still cannot prevent the vast majority of breast cancer deaths…. There will come a time when all the study patients have been followed up, all the analyses have been done, all the expert groups have met, and all the editorials have been written, and we still won’t be sure how much benefit and how much harm are caused by mammography. We must find good ways to help women deal with this uncertainty, for that time is imminent” (Goodman 2003).
By Ralph Moss
Cancer, Mammograms and Radiations Part 4
Similar Posts:
- None Found
|
|
|
|
|
 |
