Are Mammograms Getting Better?


The next time you go for a mammogram, a computer could be giving your radiologist an extra pair of eyes or providing him or her with sharper images.

Radiologists say two newer technologies will affect the future of mammography: Computer-aided detection (CAD) and digital mammography (DM), which provides clearer images.

“For women, it’s an exciting time. There are a lot of technological improvements,” says John Lewin, M.D., an assistant professor of radiology and director of breast-imaging research at the University of Colorado Health Sciences Center in Denver. “The computer still can’t read a mammogram, but it can help prevent human error by pointing out areas that might be cancer.”

Regular mammograms for women ages 40 and older have lowered breast cancer mortality by as much as 30 percent in the last three decades, studies show.

However, traditional film mammograms have two limitations: They either miss cancer that is present, or they sometimes result in false positives. That is, they find something that turns out not to be cancer, according to the National Cancer Institute (NCI).

“There are plenty of cancers you just can’t see on a (film) mammogram, even if you know they are there,” states Lewin. For example, a woman may have a lump in her breast that can be felt and is visible on ultrasound but not on a mammogram. There are other problems with film mammograms: Certain cancers look more like normal tissue on a mammogram, and some cancers may be missed because they’re very subtle or because of human error.

CAD: a radiologist’s “spell check”

CAD doesn’t replace film mammograms; it acts as a “spell check” or an extra pair of eyes for radiologists by reading and recognizing characteristics often associated with a cancer. It also marks suspicious spots for a radiologist’s further analysis.

In its first test in clinical practice, researchers at Women’s Diagnostic and Breast Health Center in Plano, TX, screened 12,860 women for breast cancer using CAD in the interpretation of each mammogram. Compared with a radiologist’s screening alone, CAD increased the number of cancers detected by 20 percent. All eight of those cancers were in very early stages when they are most easily treated, according to Timothy W. Freer, M.D., director of the Women’s Diagnostic and Breast Health Center and principal investigator of the study.

“The challenge in diagnosing early breast cancer is detecting very subtle abnormalities on the mammogram,” says Freer. “CAD simply enhances our ability to detect these abnormalities at the earliest possible time. When you put the radiologist and CAD together, clearly we are better than either is alone.”

The drawback with CAD is that more women may be called back for further evaluation, and more women may receive a biopsy as the result of an abnormal mammogram. Both the “recall” and biopsy rates in the Texas study increased by 20 percent with CAD, which is directly proportional to the 20 percent increase in cancer detection.

Current CAD systems are more accurate in the detection of suspicious calcium deposits than breast masses, says Freer. “But as the technology evolves, it should continue to improve our detection of masses, as well,” Freer says.

Digital mammography’s sharper image

Women may welcome the new digital type of mammography for two reasons: It does what film does with fewer pictures and reduces the number of times they need to be called back for a second mammogram, which is often an anxiety-ridden experience.

Digital mammography also means faster exams. A DM image is available in about 10 seconds versus two minutes for a conventional film mammogram, which must be developed. Because DM images are computerized, they are also faster and easier to retrieve. Radiologists will be able to share digital images via computer hookups, so breast-imaging experts can examine images taken at other locations.

However, although DM has the capability of providing sharper pictures, it has not yet shown to find more cancers than film mammography.

In a University of Colorado/University of Massachusetts study on screening mammography in which Lewin participated, 768 women had both digital mammograms and conventional film mammograms. The difference in detection rates between the two was not statistically significant, yet the results on “recalls” for further tests were encouraging. The study showed that 12 percent of women needed to be called back for a second mammogram with the DM system, compared with 15 percent called back after conventional film mammography, which is statistically significant, according to Lewin.

“While digital has not yet proven to be better than film mammography in detecting cancers, it is an early technology that is likely to improve rapidly,” says Lewin.

Both Lewin and Freer say the combination of technologies of having digital mammography read with the help of a computer is a natural marriage. Freer, in fact, says they may become indispensable to one another.

Does this mean women should make sure their next mammogram is using this latest technology? Lewin says not yet. “The important thing is not to go looking for a digital mammogram but to get a mammogram yearly.”

The NCI recommends that women in their 40s or older get mammograms on a regular basis, every one to two years. The American Cancer Society and the American College of Radiology recommend an annual mammogram.

The cost of a DM is the same as a film mammogram, but women may pay extra for a CAD reading. Lewin cautions that online services that charge to have mammograms checked by CAD only produce a reading pinpointing suspicious spots that must then be interpreted by the radiologist.

If you’re like most women, you may be wondering if there is any new technology that will make a mammogram more comfortable. “There’s nothing in the works that I know of,” Lewin says. Unfortunately, to get a good image, you have to compress the breast, he adds.

This article was posted on 12/02/2000

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