Our Bodies, Ourselves (126 page)

Mammography is the primary means of screening women at average risk for breast cancer. It utilizes a low dose of radiation to identify malignant tumors, especially those not easily felt by hand. A mammogram can also further investigate breast lumps that have already been identified, as well as other symptoms. Mammography involves X-ray radiation passing through the breast, producing an image on film or on a digital recording plate.

From 1975 to about 1990, the age-adjusted mortality rates from invasive breast cancer increased. In about 1990, they began to fall. By 2007, mortality had fallen by about one-third compared with its peak in 1989 and by 28 percent compared with 1975.
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It is not clear how much of the decline in mortality is due to screening mammography. (For a
discussion of routine
mammogram screening for all women over age forty).

Digital images can be enlarged and the contrast adjusted, enabling radiologists to concentrate on suspicious areas. This improves their ability to detect tumors in dense breast tissue. Digital images can also be stored and transmitted electronically, making it easier to consult with experts at a distance. For women under age fifty, women who are pre -or perimenopausal, and women who have dense breasts, digital mammography may work better, but for most women over age fifty, the use of digital mammography does not seem to catch cancers earlier or improve outcomes.

Ultrasound imaging—also called sonography—may be used to evaluate abnormalities that appear on regular mammograms. This technique excels in distinguishing solids from liquids, so it's useful for differentiating solid tumors from fluid-filled cysts, which are benign. Ultrasound can also be used to guide needle biopsies. Ultrasound works by creating an image from reflected high-frequency sound waves emitted by a device called a transducer, a microphone that helps magnify the sound. Ultrasound is not useful as a screening tool by itself.

Recently, two medical devices have been developed to address the problem of missed tumors following mammography in women with dense breasts, a condition present in about one-third of women having mammograms today. One of these automated whole-breast ultrasound devices has been shown in a large, well-designed study to significantly improve cancer detection compared with mammography alone.
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This technique is not yet widely available.

MRI is quite effective in detecting invasive breast cancer, but it also can falsely identify benign lesions as malignant. It is not a substitute for regular mammography, nor is it for screening of the general population. Some recommend it for screening women at very high risk for breast cancer. MRI uses a powerful magnetic field and radio frequency pulses that are processed by a computer to create images of organs and tissues. It does not use ionizing radiation (X-rays) but does require an intravenous contrast injection.

PEM is used in addition to mammography to identify small invasive cancers and ductal carcinoma in situ (DCIS)—cancer that is confined to the milk ducts. PEM is not yet widely available and may not be covered by insurance. It uses gamma rays to detect “hot spots” of rapidly growing cells, and a computer analyzes the image to determine the size, shape, and location of the mass. The efficacy of PEM is still under study.

Like PEM, BSGI is used along with mammography. It is not widely available and needs more research to determine how well it works. It may not be covered by insurance. BSGI employs a radioactive tracer to identify cancer cells.

Thermography is used to assist in the diagnosis of breast cancer, but it produces too many false-positive and false-negative results to be used alone as a screening tool. It records the temperature of different areas of the body by measuring infrared radiation. Malignant tissue generally has a higher temperature than normal tissue because of its richer blood supply and higher metabolic rate.

In the future, as less invasive and more effective approaches are sought for early diagnosis and treatment of breast cancer, newer imaging technologies that look at breast cancer at the cellular level may become more widely used if there is clear evidence of their effectiveness as screening tools. Currently, BSGI and PEM involve fairly high doses of radiation and are therefore not appropriate for routine breast cancer screening.

All experts agree that mammograms can find breast cancers when they are small, are more curable, and need less treatment. But there is disagreement among experts over how many are found or missed, how many are successfully treated when found, how many don't need treatment at all, when to begin a regular mammogram schedule, and when to end it.

For women between age forty and forty-nine, there is wide disagreement about screening mammograms
.

The United States Preventive Services Task Force (USPSTF), a highly respected expert group, issued new guidelines in November 2009 recommending that women in this age group discuss with their clinicians when to start screening and whether to begin screening at age forty after considering the benefits and risks and discussing personal preferences.

In doing so, the USPSTF retracted its previous guideline for this age group, which recommended
routine
(that is, automatic) screening every one to two years starting at age forty.

The American Cancer Society (ACS) and
the American College of Radiology (ACR), however, both continue to recommend routine screening every year starting at age forty for all women.

There is agreement that mammography reduces death from breast cancer, even in women between the ages of forty and forty-nine. The USPSTF agreed that screening in this age group was responsible for at least a 15 percent decrease in mortality. So why the different recommendations?

The USPSTF used a rigorous method of evaluating mammography studies. It relied almost exclusively on prospective randomized trials comparing death rates from breast cancer in those randomized for screening against those randomized for observation only. Since the benefits of screening mammography have been widely acknowledged, only one randomized trial started during the last twenty years (because randomizing would have to assign some women to “no mammography,” which most researchers would consider unethical). Critics of the USPSTF position assert that the weight of the USPSTF review is based on radiology studies that are out of date, but other experts dismiss this criticism.

In addition, different expert groups give different weight to the factors against and for routinely screening forty- to forty-nine-year-old women.

Factors against routine screening starting at age forty:
Breast cancer is much less common in this group than in older women; the number of false-positive tests (in which the mammogram suggests a woman has cancer, but a biopsy shows no cancer) is higher for younger women; and starting mammograms at forty would mean having exams every two years for an average of thirty-four years. Over a lifetime, a woman's chances of needing a biopsy to prove she didn't have breast cancer might be as high as 50 percent.

Factors for routine screening in women starting at age forty:
Cancers that are found in this age group tend to be more aggressive than those found in older women, and screening done every year, instead of every two years, may catch more of these aggressive cancers. While women may have to endure more biopsies, or anxiety with false-positive diagnoses, not getting screened can also produce anxiety.

It may be helpful to consider the comment of Dr. Ned Calogne, who chaired the USPSTF: “If I take 1,000 women age 40, over their lifetimes, 30 of them will die from breast cancer if we do no screening. If I screen every one of those women beginning at age 50 until she's 74, we reduce the deaths from 30 to 23. And if I reach down and screen them in their forties, I can increase that by one additional life saved—at best.”
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Most experts agree that if a woman between the ages of forty and forty-nine is identified as being at high risk, she should be regularly screened (see “What Are the Risk Factors Associated with
Getting Breast Cancer
?”

All experts agree that women age fifty to seventy-four should be screened regularly
.

Some experts say women in this group should be screened every year; others say every one or two years.

The USPSTF proposes screening every two years. It argues that the additional lives saved by screening yearly are not enough to justify an annual procedure. Screening at two-year intervals would preserve 81 percent of breast cancer mortality reduction seen with screening at one-year intervals.

The American Cancer Society and the American College of Radiology recommend screening every year. They argue that the 19 percent increase in breast cancer deaths that comes with screening only every two years is not acceptable.

For women over seventy-four, there is disagreement
.

The USPSTF makes no recommendations, because there are no randomized studies for this age group. The ACS and the ACR recommend annual screening as long as a woman has a life expectancy of five to seven years (most experts believe that the benefits of mammography compared with no mammography show up only after five years). They also note that it is easier to find breast cancer in older breasts and breast cancer risk increases with age. They also believe that the risks of screening are small.

The decision to screen or not screen in this age group, all agree, should rest on a discussion with one's clinician/primary care provider. Whether it's better to be screened every year or every two years is disputed. The incidence of breast cancer continues to increase into one's eighties, although most of these breast cancers are not as aggressive as those found in younger women.

Clearly, mammography can find curable breast cancers, even though there are disagreements about when to start routine screening. Weighing your personal preferences and concerns along with the recommendations of experts can be confusing and very stressful, especially if you have personal risk factors or friends or relatives who have faced breast cancer. Nevertheless, informed deliberation will help you make the best decision for you.