Find a breast cancer tumor when it is tiny, and a woman will probably beat the disease. Find that same malignancy when it is larger or has spread to other organs, and she is far more likely to die, even after surgery, radiation and chemotherapy. Finding breast tumors before they turn deadly is a challenge and one that medical technology has so far failed to master.
“We desperately need better breast cancer screening tools,” says Otis Webb Brawley, chief medical officer at the American Cancer Society. His organization promotes mammography in an effort to reduce the 40,000 deaths from breast cancer every year in the U.S. But that emphasis, Brawley fears, leads engineers and medical device manufacturers to presume that the problem of breast cancer detection is not worth their attention, because it has been solved. It has not. Mammograms miss up to 20 percent of tumors, and an average of one out of 10 readings mistakenly identifies healthy breast tissue as possibly malignant. Those false positives mean that women who try to do the right thing by going in for routine cancer screening face a substantial risk of needless biopsies (which can themselves be disfiguring and interfere with treatment later on) and expense, as well as the misplaced fear that they have cancer when they really do not.
Mammography’s shortcomings have spawned controversy and confusion. In 2009 the U.S. Preventive Services Task Force (USPSTF) determined that routine mammograms would save too few lives of women ages 40 to 49 to justify the number of false positives and unnecessary biopsies that would result in that age group. Medical societies and patient advocacy groups attacked the recommendation; the American Cancer Society still advises women in their 40s to undergo mammography every year. Some health experts fret, though, that the USPSTF finding has discouraged more than a few women, not just those in their 40s, from getting tested. “It’s made women more skeptical about the test,” says Sheryl Gabram-Mendola, a surgical oncologist at Emory University’s Winship Cancer Institute. “Women say, ‘I’m just not going to do it, I’m too busy.’”
Even before the 2009 controversy, however, women were forgoing screening mammograms. According to the most recent data from the U.S. Centers for Disease Control and Prevention, the percentage of women who have undergone mammograms within the previous two years has dropped a bit across all age groups. For women 40 to 49, the number fell from 64.3 percent in 2000 to 61.5 percent in 2008—which makes sense if mammograms are unhelpful as screening tests in that age group. For women 50 to 64, it fell from 78.7 percent in 2000 to 74.2 percent in 2008—which is worrisome given that the evidence shows mammograms are clearly beneficial for women 50 and older.
Better tools could help encourage screening and make it more useful for women of all ages. No method currently under study is robust enough yet to supplant mammography. But researchers and clinicians hope that a greater understanding of the physiology and biochemistry of breast cancer, combined with more dexterous technology, will one day result in screening tools that can replace or inexpensively supplement mammograms so that the results will be more trustworthy.
Mammography, which has been used to detect tumors since the 1970s, misses some cancers and wrongly suggests the presence of others because it is based on low-dose x-rays, which have inherent limitations in their ability to resolve tumors. When viewed with x-rays, a malignancy appears lighter in color than does normal breast tissue. X-rays also pick up white specks of calcium deposits that may be generated by a tumor as it grows. But x-rays are not good at spotting tiny tumors, partly because of a lack of contrast and partly because the calcifications associated with tumors are much smaller than benign deposits and therefore easy to overlook. Nor are x-rays good at detecting tumors in dense breast tissue, which also reads as white; many women younger than 50 have dense breasts. Finally, mammograms cannot indicate for sure whether an unusual mass is cancerous.