A properly working mammogram machine will, under the best of circumstances, miss up to 20 percent of cancers, according to the National Cancer Institute (NCI), and because your results are based on the radiologist's opinion, they're somewhat subjective. "A test is only as good as the combination of the machine and the person doing the interpreting," says Eric Winer, MD, chief of the division of women's cancers at Boston's Dana-Farber Cancer Institute and a professor of medicine at Harvard Medical School.
One reason for incorrect readings is the fact that film mammography, which until recently was the only kind used by the majority of screening facilities in the United States, is often not sensitive enough to detect tumors in women with dense breasts. For these women as well as women under the age of 50 (younger women tend to have denser breasts), digital machines are a better choice, according to a 2005 NCI-sponsored trial that compared film mammography with digital.
Another issue is faulty practices at some screening centers, which violate standards enforced by the FDA—everything from failing to test the machines on a weekly basis to grave (but thankfully rare) violations like placing the wrong patient information on the ID section of the film or allowing an inadequately trained technician to run the test. Such violations are discovered through annual inspections federally mandated by the Mammography Quality Standards Act (MQSA). While these inspections go a long way toward ensuring accurate tests, they also reveal some troubling problems. Of the 8,713 certified screening facilities in the United States that had undergone an inspection as of September 1, 23 percent had been cited for minor to serious violations. Last year a CBS station reported that 92 Los Angeles–area mammography facilities had failed their annual inspection. And even though MQSA requires that screening centers make their inspection results available to patients, most women don't know to ask for them.
After hearing about the potential for irregularities, Jenny Oropeza, a California state senator, went for a mammogram. "I was curious, so I asked the radiologist for the latest inspection report," she says. "I was told it wasn't available. I knew that they didn't have to post it, but they did have to tell you. That's when it hit me: We need to do a lot here." In February 2009, Oropeza introduced a bill requiring all California facilities to post inspection results in a visible location. At press time, the bill was awaiting Governor Schwarzenegger's signature.
So what can you do to maximize the reliability of your next mammogram? Learn your rights. Your testing facility is required to send you your results within 30 days of your exam, and must transfer your original mammograms to you, your doctor, or a specific facility if you so request. Prior to your mammogram, the technician must ask if you have breast implants and address any specific concerns you raise. If you feel any of these rights have been violated, ask to speak to the person at the facility who handles complaints and state your grievances. If you feel that your concerns haven't been resolved, you can file a complaint with the American College of Radiology or call the ACR Mammography Accreditation Program at 800-228-6440 for more information.