Detecting Breast Cancer: An Image Problem

MRIs often aren't the best diagnostic tool for low-risk patients

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MONDAY, June 16, 2003 (HealthDayNews) -- In the high-stakes world of breast cancer, the traditional mammogram often finds itself pitted against the newer, more technologically savvy magnetic resonance imaging (MRI) as the best way to identify malignant tumors.

Now, a study in the June 15 issue of Cancer shows a woman's risk of the disease could be an important factor in determining whether she benefits from an MRI.

"Our research shows that the benefits of MR screening in low-risk women are small, while the disadvantages of such a screening in this group are high," says study co-author Dr. David Dershaw, director of breast imaging at Memorial Sloan-Kettering Cancer Center in New York City.

Conversely, says Dershaw, for women at high risk for breast cancer, an MRI screening can be an important tool.

"The goal here is to know, going into the screening, who is at high risk and who is not, so you know who will benefit from an MR and who will not," Dershaw says.

Because an MRI can be ultra-sensitive in picking up what looks like breast abnormalities, a false-positive finding can be common in women at low risk for cancer. This, he says, often leads to an unnecessary biopsy.

And since biopsies result in scar tissue that can compromise future imaging, the unnecessary treatment is detrimental on two fronts.

New York University oncologist Dr. Julia Smith agrees.

"As more tests become functionally based, the more scar tissue you have, the more difficult it can be to sort out what is going on," she says.

Moreover, says Smith, the psychological and emotional trauma of a false-positive diagnosis can be great.

"You don't want to be unnecessarily putting women through something this dramatic unless it's going to have a positive impact on their health and their health care," says Smith, a clinical assistant professor at New York University's School of Medicine.

The new study is a retrospective look at the medical records of 367 women at high risk for breast cancer. None of the women reported any symptoms, and each had a normal mammogram result. These same women subsequently underwent their first MRI screening.

It was during the MRIs that breast abnormalities were discovered. Ultimately, a diagnosis of "probably benign" was given to 89 of the 367 women who had the MRI -- equal to about 24 percent. After a second follow-up MRI (on average within 11 months), 20 women had biopsies.

Of those 20 women, malignancies were found in 9, constituting 45 percent of the women who underwent biopsy and 10 percent of the original 89 diagnosed with "probably benign" lesions.

The bottom line: "The study showed that women at high risk for breast cancer would benefit from an MR, but women at low or normal risk would not," Dershaw says.

Further, he says that knowing a woman's risk profile before MRI screening is the best way to determine how accurate that diagnosis will be.

Smith says it's this kind of information that ultimately will give every woman the opportunity to get the most accurate screening result possible, regardless of her risk status.

"This study was the first step towards establishing a more personalized screening criteria, one from which all women ultimately will benefit," says Smith.

More information

To learn more about MRI screening, visit The American College of Radiology. To learn more about mammography, check with the U.S. Food and Drug Administration.

SOURCES: David Dershaw, M.D., director, breast imaging, Memorial Sloan-Kettering Cancer Center, New York City; Julia Smith, M.D., oncologist and hematologist, New York University Medical Center, and clinical assistant professor, New York University School of Medicine, New York City; June 15, 2003, Cancer
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