Q&A: Breast MRI Shows Its Strength

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The numbers are alarming: the American Cancer Society estimates that in 2004, more than 200,000 American women will be diagnosed with breast cancer and 40,000 will die from the disease. While x-ray-based mammography screening of women over 40 is recommended, guidelines eventually will change as diagnostic tools for breast imaging such as breast magnetic resonance imaging (MRI) and ultrasound are better understood throughout the clinical community.

Studies are further defining the role breast MR plays in the diagnosis and treatment of breast cancer. Just last month, a study published in the New England Journal of Medicine concluded that MRI may be better than mammography in detecting breast tumors in women who have a family history of or genetic predisposition to breast cancer. The findings came from Erasmus Medical Center in Rotterdam and suggest that MRI be used in addition to mammography for this group of patients.

In June, the International Breast MRI Consortium (IBMC) presented a study at the American Society of Clinical Oncology that said breast MRI is more than twice as effective as mammography in detecting the number and extent of breast cancer tumors. The first international, multi-site study of more than 1,000 women at 17 institutions in the United States, Germany and Canada discovered that out of the 428 women who had breast cancer, breast MRI detected additional cancerous lesions in 56 women, while mammograms detected additional lesions in only 17.

Mitchell Schnall, MD, professor of radiology and associate chair for research, department of radiology at the University of Pittsburgh Medical Center (UPMC) was principal investigator of the study. Schnall has helped expand breast imaging services at UPMC that now include digital mammography, ultrasound, MR and positron emission tomography. The center performs approximately five to six breast MRI scans on research protocols per week and about 25 to 30 clinically per week.

Health Imaging & IT spoke with Schnall about the state of breast MRI, its promise as a supplemental tool to mammography and its role in improving treatment options for women with a diagnosis of breast cancer.

Q: The International Breast MRI Consortium's study concluded that breast MRI is significantly better than traditional mammography in detecting the presence and extent of disease in patients diagnosed with breast cancer. What role does breast MRI play today in the diagnosis and treatment of breast cancer?

A: If one looks at the two major areas where MRI has been used at large, multi-center studies, one is our study that shows that in patients with breast cancer, it is important to understand the extent of disease to appropriately plan therapy. One of the things our study showed is that MRI is significantly better at looking at the extent of disease than mammography is within the breast. We believe that MRI has the potential to reduce the local recurrence rate for breast conservation therapy by as much as 5 percent. So in addition to looking at the extent of the disease, breast MRI has potential for looking at the other breast in women with cancer and screening women who are particularly at high risk for breast cancer.

Q: What patients are ideal candidates for breast MRI?

A: There are two populations of patients: patients who have a breast cancer diagnosis and patients who are at a particularly high risk for breast cancer. And it's not just women with a relative who has had breast cancer. There are other non-relative risk factors, such as a diagnosis of ductal carcinoma in situ (DCIS), diagnosis of atypical hyperplasia, radiation therapy for Hodgkin's disease as a child and carrying a breast cancer susceptibility gene.

The sensitivity for breast MRI in the detection of invasive breast cancers larger than 3 mm approaches 100 percent.

Q: Why is this so?

A: Mammography [presents] a projection image and it relies on subtle architectural findings and the visibility of calcifications to find cancer. Breast MRI really relies on the blood flow. We give [the patient] a contrast agent and watch an enhancement that the contrast agent causes. So the first thing is that it is not so sensitive to overlying adjacent breast tissue, such as mammography is. Therefore, you don't run into problems with a dense breast. The second thing is that the enhancement is typically pretty striking. These things make it relatively straight-forward to detect breast disease. The big challenge in MRI is making the cut off