For women with abnormal mammograms (search) and possible breast cancer, MRI (magnetic resonance imaging) (search) won’t eliminate the need for a breast biopsy, new research shows.

Breast MRIs are highly sensitive in detecting breast tissue abnormalities but only moderately specific at determining which abnormalities are true breast cancers, says lead researcher David A. Bluemke, MD, PhD, a radiologist with Johns Hopkins Hospital.

His report appears in the latest issue of The Journal of the American Medical Association (JAMA).

Recent studies have shown that MRI holds great promise in detecting early-stage breast tumors in women at high genetic risk. These women are typically very young women with dense breast tissue, which can make mammograms difficult to read and interpret. MRIs give doctors a much better view of the breast than mammograms do because they are not heavily influenced by breast tissue density.

However, despite how sensitive this technique is in determining abnormalities of the breast, MRI is costly, and detected abnormalities aren't necessarily cancers. Whether it’s useful for screening women at normal risk of the disease has not been examined.

Today’s study compares breast MRI plus mammography against mammography alone in evaluating suspicious breast tumors. The question: Is MRI really a better option in diagnosing breast cancer? And can it offset the need for a biopsy to confirm diagnosis?

The study involved 821 patients about 53 years old who were referred for a breast biopsy. Among these patients, 404 malignant tumors were diagnosed. Researchers found:

MRI correctly detected 88 percent of cancers in 404 cancer cases. MRI correctly identified as negative 68 percent of noncancer cases.

Overall, MRI predicted 73 percent of positive cancer cases, while mammography identified 53 percent of cancers.

Although MRI can pick up more cancers than mammography, it doesn’t rule out the need for a biopsy for confirmation of cancer, he writes.

Overall, while the sensitivity of MRI to detect breast abnormalities was high, the technology was only moderately specific in determining which lesions are cancerous. Researchers say that because of this, it may not be possible to avoid biopsies of breast lesions that appear to be suspicious on a mammogram.

By Jeanie Lerche Davis, reviewed by Brunilda Nazario, MD

SOURCES: Bluemke, D. The Journal of the American Medical Association, Dec. 8, 2004; vol 292: pp 2735-2742. WebMD Medical News: “MRI Beats Mammogram for Women at High Risk.”