Feature Article

Ultrasound Screening With Dense Breast Tissue

There are a number of effective ways to screen for and diagnose breast cancer, ranging from standard mammography imaging to different kinds surgical biopsies. The most common techniques include:

While each of these techniques has important advantages depending on an individual patient's circumstances, ultrasound is becoming an increasingly prevalent screening and diagnostic tool. It appears to be especially beneficial for women with dense breast tissue, as well as for providing a "second opinion" when initial mammography results are inconclusive.

Understanding Ultrasound

More than 700,000 women undergo breast biopsies each year. But nearly 80 percent of these biopsies are benign (non-cancerous). In effect, if a more accurate non-invasive diagnostic technique were available, hundreds of thousands of women would be spared from unnecessary biopsy procedures.

While ultrasound is certainly not the answer to this dilemma, it is clearly a step in the right direction. One study estimated that the use of ultrasound could eliminate as many as 20 percent of these invasive biopsies. Furthermore, unlike a mammogram that uses a small (and safe) amount of radiation, ultrasound is a noninvasive test that uses sound waves. It also doesn't require the breast compression that many women find painful in mammograms.

Breast ultrasound has been used extensively in Europe and Japan, but it has been slow to catch on in the United States. It involves sending high-frequency sound waves through the breast, which are then picked up and translated by a computer into an image that is displayed on a screen. Ultrasound can detect the increased blood flow common to cancers and can distinguish between cancerous and noncancerous cysts. It can also be used to help doctors precisely guide a biopsy needle into breast lesions.

However, ultrasound's use as a regular screening tool for most women is not recommended because small calcium deposits, which are one of the earliest signs of breast cancer, are not visible by ultrasound.

Dense Breast Tissue

Approximately two-thirds of premenopausal women have dense breasts. In postmenopausal women, about one-quarter have dense breasts, and the rate increases to about half of postmenopausal women who take hormones. Breast density is the most significant factor in predicting the sensitivity-and thus accuracy-of a mammogram. As the density of breast tissue increases, the sensitivity of a mammogram decreases.

A major study last year by a group of radiologists in New York City found that a combination of mammography and ultrasound can provide dramatic improvements in detecting breast cancers in women with dense breast tissue. Dr. Thomas Kolb and colleagues conducted more than 18,000 breast cancer screenings using mammography, ultrasound and physical clinical exams, either alone or in combination.

Breast density is traditionally rated on a scale of one to four, with Grade Four being the most dense. The researchers found that a combination of mammography and ultrasound detected 100 percent of the breast cancers in women with Grade Two density breasts, 94 percent in women with Grade Three, and 88 percent in women with Grade Four density breasts.

Mammography alone detected 83 percent of cancers in women with Grade Two breast densities, decreasing to just over half (55 percent) in women with the densest breast tissue. Conversely, ultrasound, when used alone, detected two-thirds (66 percent) of the cancers in Grade Two, but improved to a 75 percent detection rate in Grade Four density breasts.

Physical examination of breast tissue (without mammography or ultrasound) was found to be the least sensitive method of detecting breast cancers, and by the time tumors could be felt they were usually in a more advanced stage.

Kolb explained that ultrasound is more effective than mammography in detecting cancer in women with dense breasts because of its ability to "contrast" breast tissue. In ultrasound, dense breast tissue appears white, while the cancer is dark. Conversely, in a mammographic image, both the dense breast tissue and the cancer are white, making it more difficult to distinguish between the two.

Regular Screening is Crucial

While ultrasound and other techniques are proving valuable in detecting breast cancers at earlier, more treatable stages, regular mammography screening still remains the most effective early screening option for women. The American Cancer Society and most cancer organizations strongly recommend that every woman have a mammogram each year beginning at age 40.

SOURCES:

American Institute of Ultrasound in Medicine (http://www.aium.org)
The Susan G. Komen Breast Cancer Foundation (http://www.komen.org)
The American Cancer Society (http://www.cancer.org)

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