Behind the screens: mammograms.

For most of the 20th century, physicians thought that breast cancer was a local disease that only spread to the rest of the body late in its course. Early detection ... meant that the cancer would be caught and treated before it could kill.... We know now that breast cancer is an extremely complex disease that often spreads invisibly through the body when a breast lump is small. Cancers detected while small may not, in fact, be early. The aggressiveness of a cancer ... helps determine a woman's fate.

--Barron Lerner, NY Times (12/14/2001)

There are three ways in which breast cancer is typically discovered--by breast self-examination (BSE), by clinical breast examination (CBE) performed by a doctor or nurse, and by mammography. All three methods have generated controversy but perhaps the most controversial of all is mammography.

Types of mammography

Mammograms are of two types: screening and diagnostic mammography. The most widely known is the screening mammogram endorsed by most cancer organizations, and typically recommended to women at high risk for breast cancer aged 40-49 or for any woman aged 50-79. Women under 40 are not encouraged to have mammograms unless they have inherited a breast cancer gene or are otherwise considered to be at exceptionally high risk.

Diagnostic mammography is ordered when an anomaly (abnormality) is found either on a screening mammogram or during CBE or BSE. Most of the information in this article applies primarily to the screening mammogram.

What is involved?

Mammograms are conducted by a specially trained technician (nearly always female) who escorts the woman into a small room, positions her so that her breast is squeezed between two plates--once horizontally and once vertically--and then retreats behind a lead shield to take a picture. Women with very large breasts may require more than two exposures per breast. The squeezing can be very painful, particularly for women whose breasts tend to have a lot of fibrous tissue (fibrocystic breasts) or women with fibromyalgia, but the pain lasts only a few seconds. Once the plates are checked, the woman is free to go. Later, a radiologist reviews the films.

Perils of mammography

Aside from the pain involved (and this seems highly variable), there is a degree of danger to ionizing radiation itself. Although radiologists downplay the hazards, the cumulative effect of radiation, year after year, may add to one's risk of cancer. It is estimated that four films of a regular mammogram add up to one rad of exposure and that each rad increases the risk of breast cancer by 1%. Over ten years of annual screening this means a cumulative increased risk of 10%. This is partly why younger women are discouraged from regular mammograms. (Women carrying an inherited gene for ataxia-telangiectasia--a rare degenerative condition--are highly susceptible to ionizing radiation damage).

There is also some concern about breast compression potentially causing a rupture of blood vessels in or around small undetected cancers. This is a theoretical peril since it is difficult to establish for certain if it warrants concern.

How effective is mammography?

According to the US National Cancer Institute (NCI), mammography misses approximately one breast cancer in five. Either the breasts are so dense that the tumor is obscured, or the tumor is "out of the picture"--deep in the armpit or higher up near the collar bone. Moreover, even when satisfactory plates are available, the most experienced radiologist will accurately read no more than seven out of ten sets of film. Less experienced doctors will not do as well. These missed diagnoses, or "false negatives," are more common for premenopausal women with dense breasts or postmenopausal women on estrogen therapy.

There are also "false positives." In about four to five percent of cases (with some new studies indicating 5-15%) a woman will be told that she has an abnormality--a potential cancer that warrants further investigation. If she is having annual mammograms, her likelihood of receiving a false positive after a number of years increases. Unfortunately, the resulting investigation often involves surgical biopsy (and a resulting scar) before she is given the "all-clear."

Many false positives are based on a diagnosis of ductal carcinoma in situ (DCIS), a pre-invasive cancer often described as "microcalcifications." In about 80% of cases, DCIS never becomes invasive. Furthermore, mortality from DCIS (-1%) is about the same for women whether treated or untreated.

These are not encouraging statistics and belie the enormous publicity given to mammographic screening as a way of "saving women's lives." In fact, as the NCI acknowledges, mammography extends perhaps one life for every 1,700 to 5,000 women screened and followed for 15 years. For women between 50 and 69, four out of a 100 will develop the disease, and one in four of these women will die of breast cancer. In other words over 99% of the women in this age group receiving mammograms will not materially benefit from the procedure, aside from peace of mind, and will be exposed to unwanted radiation.

The latest controversy

Most of the claims for the benefits of mammography are based on eight international controlled trials involving approximately 500,000 women. A few years ago, two officers of the Nordic Cochrane Center in Copenhagen were asked to investigate the mortality data from Sweden, which showed no drop in breast cancer death rates even though women there have been encouraged to have regular mammograms since 1985. (Cochrane Centers are part of an international organization that helps people make well-informed decisions about health care by ensuring the accessibility of systematic reviews of the effects of health care interventions.) The researchers subsequently published a study that dismissed five of these eight studies as deeply flawed and, using data from the acceptable studies, argued that mammography did not affect the mortality rate for women with breast cancer.

On the basis of this analysis, an independent panel of experts in the US announced that there was insufficient evidence to show that mammograms prevented breast cancer deaths. The NCI rejected this opinion and continued to press for screening mammograms. A year later, the Danish researchers produced a second analysis suggesting that levels of false positives during screening mammography in the US lead to unwarranted aggressive treatment and ultimately to a higher than normal number of mastectomies.

This set the cat among the pigeons and the resulting furor has not really died down. Swedish investigators, stung by the Cochrane Center analyses, published a couple of detailed reports contending that breast cancer screening has in fact led to a reduction in death rates of approximately 20% for women aged 40 to 49, and approximately 30% for women aged 50 to 69. While reassuring, one must bear in mind that 85% of Swedish women have regular mammograms, with consistent intervals between screenings. The benefits cited for Sweden would be attenuated in other countries.

Why is mammography so popular?

One answer is that breast cancer is big business. The mammography machines and film produced by General Electric, DuPont, Eastman Kodak, Piker and Siemens are worth millions of dollars and are being constantly updated to produce sharper, clearer pictures. Personnel from these firms also conduct research evaluating their products (research used by the cancer societies), sponsor cancer awareness programs, produce advertising and promotional literature for clinics, hospitals, medical organizations and physicians, and lobby the US Congress to promote the availability and benefits of mammography. Mammography clinics employ thousands of radiologists (five of whom have served as presidents of the American Cancer Society), as well as technicians, repairmen and a host of other employees. Breast cancer is an industry and a robust part of our capitalist economy. Within this environment, women worry about breast cancer and seek reassurance from technology.

Are there alternatives?

Another reason why mammography is so popular is because there is no viable technological procedure to take its place. We hear about ultrasound, thermography, magnetic resonance imaging (MRI), digital mammography and ductal lavage. Of these, only MRI is mentioned as a possibility on the website of the NCI. And none has been demonstrated to lower mortality from breast cancer.

Ultrasound imaging of the breast is used to distinguish between solid tumors and fluid-filled cysts, and can also be used to evaluate lumps that are hard to see on a mammogram. It is rarely used for routine breast cancer screening because it cannot consistently detect early signs of cancer such as microcalcifications, even though microcalcifications may not indicate any real threat.

Thermography uses ultra-sensitive infrared cameras and sophisticated computers to detect, analyze and produce high-resolution diagnostic images of temperature variations, which may be among the earliest signs of breast cancer. However, there is still a need for more research to compare outcomes with other methods.

MRIs are used to evaluate palpable breast masses and to discriminate between cancers and scars, but false positive results are common. MRIs are therefore used primarily to assess the integrity of silicone breast implants, of palpable masses following surgery or radiation therapy, and to detect breast cancer recurrence where mammography and ultrasound prove inadequate.

Digital mammography--once heralded as a breakthrough--has been shown to better facilitate storage, retrieval, transmission and adjustment of images, but so far has not shown any greater accuracy than standard mammograms.

Ductal lavage--developed by Dr. Susan Love--is very new. It is a procedure that samples cells from the milk ducts of the breast through nipple fluid to identify women at high risk of breast cancer. It has been approved in the US only for high risk women, in conjunction with mammography, and the first clinical practice guidelines were issued as recently as January of last year.

What about BSE and CBE?

Breast self-examinations have been promoted for years on the basis that the earlier a cancer is discovered, the better the prospects of a total remission (doctors rarely say "cure"). In fact, roughly one-third of breast cancers are diagnosed in the interval between annual mammogram and over 90% of all breast cancers are detected by the woman doing BSE, in the shower or, with her partner, during intimate moments. Even so, a recent report published in Canada has recommended that routine teaching of BSE be excluded from regular medical checkups for women of all ages (See AFI, Vol. XVIII, No. 5, Nov.-Dec. 2001).

The rationales for this recommendation were to spare physicians from having to cope with a roster of breast complaints, and to spare women from the unnecessary biopsy procedures that often follow. This recommendation did not deal with the possibility of having nurses teach BSE and the more important aspect of the sense of control felt by many women who routinely use BSE.

Many women prefer not to do BSE. For those that do, the Canadian Breast Cancer Network and other breast cancer organizations recommend the use of all screening tools--BSE, CBE and mammograms.

A recent and very credible study of clinical breast examination demonstrates that, when done properly, CBE is as effective, perhaps more effective, than mammography. The only hitch is that the CBE in this study was performed by trained nurses who spent eight to ten minutes on the procedure. If our health care providers were similarly thorough, CBE would be a welcome alternative to mammography.

A personal note

To date, the evidence that routine mammography screening allows early detection and treatment of breast cancer remains questionable. The central issue for women worldwide is the lack of a proven alternative--which makes the endorsement of mammography by the NCI, the cancer societies, and organizations that represent breast cancer survivors, more than understandable.

"The emphasis on mammograms has put the burden of fighting the disease squarely on the women themselves," say Barbara Ehrenreich and Barbara Brenner (two breast cancer survivors), and what we must do is to "band together to demand better treatments, more research into the causes of the disease and more reliable methods of detection." Amen, say I.

My own experience with breast cancer resulted from a spot discernible on a mammogram but impossible to feel (even when I knew where it was). After tracking it for a number of months, I agreed to surgery and radiation. That was five years ago. Today, I veer between being grateful that the lump was discovered during a routine mammogram and wondering whether, had it been left alone, would it ever have amounted to anything more than a small lump? I will never know.

Selected Reference:

Baxter, Nancy, Can Med Assoc Jrnl 2001;164(13):1837-1846.

Ehrenreich, B. and B. Brenner, www.newsday.com/news/opinion/ny-vpehr282526210dec28.story

Elmore, Joann G. et al, J Natl Cancer Inst 2003;95:1384.

Epstein, S.S. et al, Intnl Jrnl Hlth Serv 2001;31(3):605-615.

Fletcher, S.W. and J.G. Elmore, NEJM 2003;348:1672-1680.

Gotzsche, P.C. and O. Olsen, Lancet 2000;355:129-134.

Lerner, Barron, The Breast Cancer Wars (Oxford U. Press, 2001).

Miller, A.B. et al., Ann Intrn Med 2002;137(5):305-312.

Miller, A.B. et al., Jrnl Nat Cncr Inst 2000; 92(18):1490-1499.

Nystrom, L. et al., Lancet 2002;359:909-919.

Olsen, O., P. E. Gostzsche, Lancet 2001:358:1340-1342.

Tabar, L. et al., Lancet 2003; 361:1411-1417.

RELATED ARTICLE: Mammography: what organizations are saying ...

* BY THE EDITORS OF AFI

As the debate continues on the pros and cons of mammography, here's what a variety of leading organizations, societies and advocacy groups are recommending for those not at a high risk of developing breast cancer. These organizations regularly review their recommendations and we'll keep you up to date with any major changes in their policies.

Recommends annual screening for those 40 years and older:

* Canadian Breast Cancer Network

* National Alliance of Breast Career Organizations, US

* Susan B. Komen Foundation, US

* US Preventive Services Task Force 

* American Cancer Society

* National Cancer Institute, US

* American College of Obstetricians and Gynecologists 

Recommends screening for those 50-69 years every 1 or 2 yeas:

* Canadian Task Force on Preventive Health Care

* Canadian Cancer Society 

* Health Canada

* American College of Preventive Medicine 

* American Academy of Family Physicians 

* National Women's Health Network, US

Recommends women be counseled about the benefits and risks of mammography:

* National Breast Cancer Coalition, US

* National Institutes of Health Consensus Conference, US

Adapted from the US Preventive Services Task Force and the N Engl J Med 2003:348:17.

Janine O'Leary Cobb is the founder of A Friend Indeed, and the author of Understanding Menopause (Key Porter).