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Ultrasound as a breast cancer test is becoming more accepted

Though not routine, the procedure proves helpful in spotting disease among women who have dense tissue.

June 14, 2004|Marnell Jameson | Special to The Times

Susan Beane, a 45-year-old mother of two, had undergone regular mammograms for five years. Each time, she got a clean bill of health. But nine months after her most recent routine screening, she felt a lump.

A follow-up mammogram failed to produce a picture of the growth. It wasn't until Beane underwent an ultrasound that the radiologist found the 1.6-centimeter tumor that was eventually determined to be cancer. The disease had spread to at least one of her lymph nodes. In February, Beane had a double mastectomy.

The Castle Rock, Colo., woman said she believes that ultrasound should be part of a routine screening for women who, like her, have dense breast tissue, a category that includes about half of all women undergoing breast screening. Dense tissue can mask tumors on mammograms.

"If I'd had an ultrasound during my routine screening nine months earlier, then I would have been diagnosed sooner. The cancer probably wouldn't have spread. I wouldn't have needed chemotherapy and probably could have saved my breasts," Beane says.

Many doctors increasingly agree with that assessment. Across the country, more physicians are ordering ultrasound in addition to mammography for women whose breast tissue is dense. Currently, standard practice calls for diagnostic (as opposed to screening) ultrasound only when a mammogram or clinical breast exam reveals something suspicious.

A panel report issued last week from the Institute of Medicine and National Research Council of the National Academies supported the need to do more to detect breast cancer. The panel concurred that mammography, though still useful, wasn't always enough and that health practitioners needed to investigate other complementary screening methods.

Using ultrasound as a screening tool doubles the rate of breast cancer detection in women with dense breasts, said Wendie Berg, a Baltimore radiologist and a principal investigator for a large-scale nationwide study to further examine the benefits and efficacy of ultrasound screening.

"Mammography depicts about three to five cancers per 1,000 women,'' Berg said. "In women with dense breasts, studies have shown, ultrasound depicts another three cancers per 1,000 women. Significantly, the cancers found only on ultrasound are almost all small invasive cancers that have not yet spread to the lymph nodes and therefore have good prognoses."

Other doctors say it's too early to make ultrasound routine for screening purposes. They say that the data to date don't justify it, that the method has a higher rate of false positives -- areas that look suspicious but that are shown by biopsies to be benign -- and that the cost and availability of good screeners make widespread screening impractical.

Daniel Kopans, director of breast imaging at Massachusetts General Hospital and professor of radiology at Harvard Medical School, is an outspoken critic. There is no proof that the test saves lives, he said in a recent interview.

And as he wrote in an opinion paper published in the November 2003 issue of the American Journal of Roentgenology: "We need more supportive evidence before we screen and potentially needlessly scare women. We need to be certain the test will do more good than harm."

He's especially concerned about the rate of false positives. "These are unavoidable and result in anxiety, recall of patients for additional evaluations, biopsies, useless and unnecessary treatment and inconvenience," his paper said.

Depending on the center, a woman runs a 2% to 6% chance of undergoing an unnecessary aspiration or biopsy as a result of screening ultrasound, Berg said. (In a 2002 study, the false-positive rate of biopsy was 2.4%.) By comparison, the false positive biopsy rate following mammography is 1% to 2%, Kopans said.

Cost and resources pose other barriers to routine ultrasound screening. Insurance companies typically don't cover the $150 to $450 test. And the reliability of the tests depends on the person reading the results. "Not enough centers have the equipment or the expertise to do these studies well," Berg said.

But despite the drawbacks, some experts say ultrasound is a useful tool that -- based on studies to date -- reveals significantly more cancers than does mammography alone in women with dense breasts. These cancers tend to be small invasive cancers in an early stage.

In the 2002 study, conducted by New York radiologist Thomas Kolb and published in the journal Radiology, 11,130 women who had no signs of breast cancer each had a mammogram followed by a clinical examination. Women who had denser (as opposed to fatty) breasts (49%) also underwent an ultrasound. Overall, cancer was found in 221 women.

The study found that mammography detected 98% of cancers in women with fatty breast tissue, but only 48% of the cancers in women with the densest breasts. Ultrasound added to the mammography screening revealed another 46% in that group, or 94% of the cancers. (The clinical exam found the remainder.)

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