Recent reports touting the benefits of MRI screening for breast cancer have caused some understandable confusion. For most healthy women who have only an average risk of developing breast cancer, the screening recommendations developed by the American Cancer Society (ACS) remain unchanged: annual clinical breast examination and mammography beginning at age 40. Yet for some women at high risk for breast cancer and for women who have newly diagnosed cancer in one breast, the new ACS guidelines and a recent study in the New England Journal of Medicine suggest that MRI should be added to their screening plan.
Breast MRI
Magnetic resonance imaging (MRI) is a diagnostic procedure that uses a magnetic field to provide three-dimensional images of internal body structures, including the breast. MRI scans are more sensitive than mammograms, in some cases detecting breast cancer in high-risk women with no obvious symptoms, such as lumps or unusual discharge. However, this increased sensitivity can produce false positive readings, which lead to needless biopsies, additional scans, and the fear and anxiety that may accompany them. MRI is also relatively expensive, with costs running between $1,000 and $2,000 -- a figure which, at the top of the range, is up to ten times the cost of mammography. In some cases, MRI screening for breast cancer is not covered by insurance or Medicare.
In addition, MRI, which uses advanced equipment and software, requires specially trained radiologists to read the results. The ACS estimates that there could be a million or more high-risk women a year who would benefit from MRI screening. Some breast cancer experts question whether there are enough MRI machines and radiologists to read the scans to meet the increased demand that will be created by the new guidelines.
As a result of these factors, the ACS, finding no benefit from MRI screening for women of average risk, does not recommend that these women seek annual MRI. Instead, the ACS suggests that they receive annual mammograms and breast exams by a physician, beginning at age 40.
Defining High Risk & High-Risk Recommendations
The ACS defines women with especially high risk of developing breast cancer as women who have a BRCA1 or BRCA2 mutation, or a first-degree relative (parent, sibling, or child) with a BRCA1 or BRCA2 mutation. (BRCA1 and BRCA2 are genes involved in cell growth, division, and DNA repair, which when mutated can increase an individual's risk of breast cancer up to 85 percent.) This very high-risk group also includes women with a 20 to 25 percent or greater lifetime risk of breast cancer, calculated by one of several accepted risk assessment tools. [The National Cancer Institute (NCI) offers a tool at: http://www.cancer.gov/bcrisktool/.] Women who received radiation to the chest between the ages of ten and 30 for the treatment of childhood cancers such as Hodgkin's disease are also classified as very high risk, as are women with Li-Fraumeni syndrome, Cowden syndrome, or Bannayan-Riley-Ruvalcaba syndrome (cancer predisposition syndromes triggered by inheritable disease-causing mutations), or a first-degree relative with one of these syndromes.
The new guidelines, published in the April issue of the ACS journal CA: A Cancer Journal for Clinicians, recommend that these women at especially high risk receive both yearly mammograms and MRI screening, which together increase the odds of finding breast cancer in its earliest form, when treatment has the greatest chance of success.
Unfortunately, these guidelines do not cover all categories of women at high risk. For some women with certain conditions -- including a 15 to 20 percent lifetime risk, calculated by an accepted risk assessment tool; very dense or unevenly dense breasts; lobular carcinoma in situ (LCIS); atypical lobular hyperplasia (ALH); or atypical ductal hyperplasia (ADH) -- the ACS notes that there is not enough evidence to either recommend or not recommend MRI screening.
New England Journal of Medicine Study
For women with newly diagnosed cancer in one breast, a study published in the March 2007 issue of the New England Journal of Medicine (NEJM) found that MRI screening of the other breast can identify tumors that a mammogram may miss.
The study's authors note that as many as ten percent of women who have had breast cancer in one breast will develop it in the other breast. If this "contralateral" cancer is detected after the completion of treatment for the original "unilateral" breast cancer, the affected woman must begin a second course of cancer therapy -- instead of undergoing a single course of therapy if both cancers had been detected at the same time. Consequently, detecting small, contralateral cancers becomes extremely important in minimizing treatment time.
The National Cancer Institute-funded, multi-center study included 969 women recently diagnosed with unilateral breast cancer who had no abnormalities detected in the other breast during either mammography or clinical examination. These women were each screened with breast MRI. For women with MRI-detected cancer, biopsies were performed to confirm diagnosis. The absence of breast cancer was confirmed by biopsy, or repeated imaging and examination.
In the study, MRI detected contralateral breast cancer that was missed by mammography in 30 women, accounting for three percent of the group. Of those 30 women, 18 had tumors that, when analyzed, were found to be invasive.
Breast MRI Screening at Memorial Sloan-Kettering
"We have been offering high-risk MRI screening for breast cancer for many years," says Elizabeth Morris, Director of Breast MRI at Memorial Sloan-Kettering and a member of the panel that created the ACS guidelines. "However, our definition of high risk is somewhat broader than the ACS guidelines."
According to Dr. Morris, women with a strong family history of the disease, women with either ductal or lobular atypia, women with LCIS, and women with a personal history of breast cancer all qualify for MRI screening at Memorial Sloan-Kettering. For the last category, she notes that MRI screening is limited to those women who are at high risk of recurrence, though, she adds, studies supporting this practice are limited.
"We are currently doing a retrospective study of MRI screening in women with a prior history of breast cancer," Dr. Morris explains. "The ACS states that there is not enough data available to recommend this screening in this important population. We are analyzing our experience to hopefully generate some data to add to the literature."
Because calculating risk remains a complex undertaking and because many women overestimate their risk, Dr. Morris counsels that women should consult with their doctors about their risk of breast cancer and the potential benefit of MRI screening.
