My first thought when I read about new research out today on mammography and ultrasound was: Wow! Are mammograms really that lousy? It turns out that mammography can detect only about half of all breast cancers in women with dense breast tissue. Scary. By combining a mammogram with ultrasound, the success rate jumps to about three quarters, according to the study published in the Journal of the American Medical Association.
Indeed, the standard test is lousy in those unlucky women who have dense breasts, since tumors, which are also dense, are tough to distinguish from normal tissue on the X-rays. About half of women under age 50 and about one-third of women over 50 have this density problem, and the younger they are, the more likely they are to have dense breasts. This gives premenopausal women a double whammy: They have no good early detection tool that's widely available and they have faster growing breast tumors, according to a study published last week.
Lots of women are blithely unaware that their annual exam might be missing something. "Radiologists are reluctant to educate women on the actual diagnostic performance of screening mammography for fear of reduced participation rates...and because of a perceived lack of alternatives," writes radiologist Christiane Kuhl, of the University of Bonn in Germany, in a strongly worded editorial that accompanied the study.
It seems we've been given an oversimplified message. We may be told that the screening X-ray reduces our chances of dying from breast cancer, which it does by 22 percent in women ages 50 and over and by 15 percent in women in their 40s. But most of us never hear that the density category marked on our mammogram determines how reliable the screening is. For example, in someone with mostly fatty tissue (known as category 1), mammograms are about 98 percent successful at finding tumors, JAMA study leader Wendie Berg tells me. She's a radiologist specializing in breast imaging at the American Radiology Services at Johns Hopkins in Lutherville, Md. For women with somewhat fatty breasts (category 2), mammograms can reliably detect about 80 percent of tumors. Those with dense breasts (category 3 or 4), however, have only a 50/50 shot at having their tumor detected before it's palpable on a physical exam. Berg says these "mammogram unfriendly" women can probably benefit from also having a screening ultrasound,which actually excels at finding tumors in dense breast tissue. (Ultrasound can't be used on its own since it misses more tumors overall than mammography.)
There are, however, some big caveats with adding ultrasound to mammography:
• A lot more unnecessary biopsies. About 10 percent of the study participants wound up having a biopsy for an abnormal finding that turned out to be benign, compared with roughly 3 percent who had biopsies from mammography alone. Considering that the combination screening increased tumor detection from7.6 per 1000 to 11.8 per 1000, that's a huge increase in biopsies. On the other hand, I, for one, would fear missed cancers more than unnecessary biopsies.
• Breast ultrasound isn't always available. Many radiology facilities don't offer it, partly because Medicare reimburses only about $87 for the screening even though it takes about 20 to 30 minutes for a radiologist to perform. "Radiologists simply can't afford to do it," Berg laments. Automated devices currently under development will probably cut the screening time, she adds, but they may not be available for a few years.
• MRI with mammography catches even more cancers. The American Cancer Society recommends that women at very high breast cancer risk (like those who carry a BRCA1 or BRCA2 gene mutation) get mammography in combination with MRI. That's based on a previous study showing that this combination detects 93 percent of cancers in those with gene mutations compared with 55 percent of cancers detected on ultrasound and mammography. The ACS says there's currently not enough evidence to recommend the $1,000 test for the vast majority of women.
• Adding ultrasound may not actually save lives. The study didn't follow women long enough to see if the improved detection led to a reduction in deaths. "The assumption in this study is that finding a cancer early will reduce your chance of dying," points out Susan Love, a clinical professor of surgery at the University of California-Los Angeles medical school and president of the breast cancer-focused Dr. Susan Love Research Foundation. "Although we [doctors] have sold this for a long time, recent data suggest that not all cancers are the same and that just finding them early may not be enough. Likewise, some cancers are very slow growing and you may not need to find them early to make a difference."
What should you do if you have dense breasts? Click here.
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