Eighty-one percent of women 50 and older and 65 percent of women 40 to 49 undergo regular screening mammography in the U.S. So it’s no wonder that a vast collateral economy has developed around the procedure, and continues to grow.

Yet not all the foundations of this economy rest on solid ground. Mammography is imperfect and, for a large population of women, it has missed breast cancer or raised unnecessary concern.

Screening mammography has traditionally been promoted using simple and direct messages. These simple messages have often been misleading. Advertisements often contain images of young women, thus heightening fears of breast cancer in this age group while masking the reality that the disease is much more common in older women. Promotions also tend to overemphasize the potential benefits of screening while remaining largely silent on its limitations. The statement “Mammography can find breast cancer as small as the period at the end of this sentence” appeared on many promos in the 1980s and 1990s, leading many women to expect too much from the technology. A 2003 survey found that many American women harbor the misconception that mammography can actually prevent breast cancer from occurring. “Screening” is not synonymous with “prevention”; mammography reduces the risk of death only by finding breast cancer early.

The public has never been educated on this nuance. So it is not surprising that when breast cancer occurs in a woman who has undergone annual screening, she and her loved ones are often shocked, angry and confused.

Mammography Misses

In the mid-1990s, when routine screening mammography was becoming widely practiced, delay in diagnosing breast cancer became the most common reason for patients to file medical malpractice lawsuits, and this is still the case. From 1995 to 2001, claims added up to more than $170 million. Even though breast cancer is most common in postmenopausal women, 68 percent of claimants in those years were women younger than 50.

Mammography misses up to 15 percent of cancers that are present (false negatives) and finds many things that are not cancer (false positives). What’s more, some of the cancers it finds could have safely gone undetected without affecting the woman’s life or health (overdiagnosis).

Part of the problem is that, on a mammogram, a noncancerous abnormality can look very much like cancer. A smooth, round lump in one woman might be a benign tumor; an identical lump in someone else might be cancer. This causes 10 percent to 15 percent of screened women in the U.S. to be recalled for more evaluation. Most (95 percent) screening-detected abnormalities are ultimately found to be noncancerous. An American woman who is regularly screened during her 40s has a 61 percent chance of getting a false positive result.

The additional testing after an abnormal mammogram typically involves specialized mammography views or ultrasound, but it may also include a biopsy. As routine screening gained widespread acceptance in the late 1980s and 1990s, the number of small (nonpalpable) breast abnormalities leading to biopsy rose drastically. This led to the development of nonsurgical biopsy techniques, such as stereotactic and ultrasound-guided core needle biopsy, which could be done in the mammography center.

Now, for every $100 spent on screening, an additional $30 to $33 is spent to evaluate false positive findings. In the Medicare population, the workup of false positive mammogram results is estimated to total $250 million a year.

False Positives

Nevertheless, Americans accept the need for false positives as the inevitable consequence of regular mammography. According to one survey, although more than 90 percent of women who had a false-positive mammogram found their experience “scary,” 96 percent reported being happy that they had the test, and 90 percent continued to have mammograms at least as often as before. In another survey, when asked how many false positives are acceptable for each life saved, 63 percent of women said 500 or more and 37 percent said 10,000 or more.

False negatives carry a cost, too, of course. Mammography misses up to 15 percent of breast cancers. It is especially likely to be ineffective in women whose breasts are relatively dense. On a mammogram, breast tissue may look mainly white, indicating that it is dense, or dark gray, when it is more fatty. Typically, younger women have denser tissue. Because cancer appears on a mammogram as a white object, looking for it in dense tissue can be like trying to see a polar bear in a snowstorm. New computer-aided technology has been developed to address this problem, but it can lead to false positives.

Because the great majority of lumps found on mammography are not cancer, many women have an ultrasound after an abnormal mammogram to see if what they have is a trivial fluid-filled cyst or a potentially serious solid mass. Ultrasound is not degraded by dense breast tissue. On the other hand, it finds a great many noncancerous lumps, so women who undergo this regimen have many more unnecessary biopsies than those screened with mammography alone.

Similarly, breast magnetic resonance imaging finds many more cancers than mammography does but also suffers from high rates of false positives. MRI is relatively expensive and, until recently, was not widely available. It’s recommended only for women at extremely high risk of breast cancer (for example, those who have the BRCA1 or BRCA2 genetic mutations).

We are seeing increasing use of both these technologies, thanks in part to what happened to Nancy Cappello. In 2004, at the age of 52, this Woodbury, Connecticut, resident was diagnosed with breast cancer two months after a “normal” mammogram. Because her breast tissue was dense, she had a relatively greater risk of cancer, despite having no family history of the disease. And her cancer was harder to detect by mammogram. After her ordeal, Cappello founded Are You Dense?, an organization dedicated to educating women and advocating for supplemental screening.

Density Difference

In 2006, thanks to her efforts, Connecticut became the first state to mandate insurance coverage for using breast ultrasound (in addition to mammography) to screen women with dense tissue. Three years later, the state went further, demanding that all mammography facilities inform patients about their breast density and suggest ultrasound or MRI for those with dense tissue.

Soon, similar legislation was pending in several other states. And efforts are under way to persuade Congress to nationalize the Connecticut model. Since at least 90 percent of mammograms show some amount of dense tissue that could potentially mask breast cancer, if Connecticut’s rules were to be adopted nationwide, some 33 million breast ultrasounds would be added to the 37 million mammograms now done annually in the U.S., increasing yearly expenditures from $4.8 billion to $7.7 billion. This figure does not include additional unnecessary biopsies generated by false positive ultrasound scans.

Of the 2.5 million breast cancer survivors in the U.S., 500,000 have stage-zero cancer, otherwise known as ductal carcinoma in situ. Before the advent of screen mammography, DCIS was practically unheard of; now it accounts for one in four or five of all new breast cancer diagnoses. This condition is poorly understood, but many experts believe that, if left alone, as many as one half of all such abnormalities would never progress to lethal invasive breast cancer. Yet because of our inability to distinguish the good actors from the potentially bad ones, all patients diagnosed with DCIS receive treatment. DCIS was partly responsible for the “epidemic” narrative that developed around breast cancer in the late 1980s to early 1990s, just as screening mammography was becoming widely practiced.

It was during this time that cause-related marketing was born, thanks in large measure to the work of Nancy G. Brinker, founder of the Susan G. Komen Breast Cancer Foundation (now Susan G. Komen for the Cure). Its annual charity 5K Race for the Cure takes place in more than 100 U.S. cities and several foreign countries, attracting 1.5 million participants annually. At this writing Komen has signed 240 corporate partners. These corporate relationships have added more than $50 million to Komen’s annual fundraising tally.

Every October, Breast Cancer Awareness Month, retail products from makeup to vacuum cleaners, breath mints to jewelry, fast food to kitchen appliances carry a little pink ribbon and vague promises to support breast cancer awareness or other efforts.

Breast cancer cause-related marketing has, of course, benefited from mammography screening, and not only because it was the mammography-induced breast cancer “epidemic” that called attention to the disease. Mammography’s tendency to overdiagnose also enlarges the population of “survivors and those who love them” -- the people most likely to be influenced by pink marketing.

(Handel Reynolds is a breast radiologist at Piedmont Hospital in Atlanta. This is the second of three excerpts from his new book, “The Big Squeeze: A Social and Political History of the Controversial Mammogram,” which will be published on Aug. 7 by Cornell University Press. The opinions expressed are his own. Read Part 1 and Part 3.)

Read more opinion online from Bloomberg View. Subscribe to receive a daily e-mail highlighting new View editorials, columns and op-ed articles.

Today’s highlights: the editors on success for female Saudi Olympians and on what the ECB must do to save the euro; Susan Antilla on Wall Street’s efforts to stymie new regulations; Caroline Baum on monetary policy getting off track; Michael Kinsley on Romney’s zero tolerance for the unsuccessful; Peter Orszag on ways to keep lowering health-care costs.

To contact the writer of this article: Handel Reynolds at bigsqueezebook@gmail.com.

To contact the editor responsible for this article: Mary Duenwald at mduenwald@bloomberg.net.