Although the NEJM study suggests the need for one MRI in women newly diagnosed with breast cancer, new ACS guidelines recommend annual MRI screening for some women. In these guidelines, published in the April issue of CA: A Cancer Journal for Clinicians, screening recommendations for women at only average risk for developing breast cancer remain unchanged: annual clinical breast examination and mammography beginning at age 40. But for women with a 20 to 25 percent or greater lifetime risk of developing breast cancer, the ACS now recommends yearly screening starting at age 30 using MRI in addition to mammography. The ACS defines women at high risk of developing breast cancer as women who have mutations of the BRCA1 or BRCA2 genes or who have a first-degree relative (parent, sibling, or child) with such a mutation. BRCA1 and BRCA2 are genes that, when mutated, can significantly increase an individual's risk of breast cancer. Women who received radiation to the chest for treatment of childhood cancers such as Hodgkin's disease are also classified as high risk, as are women with certain cancer predisposition syndromes.
Yet even given these parameters, calculating risk is not a simple proposition. "Most women overestimate their risk and aren't familiar with risk models, which are constantly being updated," noted Elizabeth A. Morris, Director of Breast MRI at the Center and a member of the panel that drew up the ACS guidelines. "They need to talk to their doctors to figure out what their true risk is."
Work done at Memorial Sloan-Kettering has been important in developing a consensus on the increasingly important role of MRI in breast cancer screening. Continuing efforts at the Center will help to determine if additional women should be screened with MRI. "At Memorial Sloan-Kettering, we're a bit more aggressive about who we include in our high-risk screening than the ACS recommendations," elaborated Dr. Morris. "We will screen not only BRCA1 and 2 patients, but also relatives of those patients and women who have a personal history of breast cancer if it was diagnosed pre- or perimenopausally. We'll also screen women with lobular carcinoma in situ, which is not actually a cancer but a marker that means a woman is at high risk for developing an invasive cancer during her lifetime." Women with a strong family history of the disease and women with ductal carcinoma in situ and growths called atypical hyperplasia also qualify for screening at Memorial Sloan-Kettering.
While the benefits of MRI screening in certain women have been demonstrated, the increased sensitivity of the scans can produce false positive readings, which may lead to additional scans, unnecessary biopsies, and anxiety in patients. "This is the reason for the current limitation of MRI screening to women at very high risk," explained Dr. Dershaw. "The likelihood that a positive MR is due to a cancer is higher in women who have a higher risk of cancer. That's why we don't want to screen women at low risk, because we would do lots of biopsies and find very little cancer. There is now the recognition that screening for breast cancer should not be the same for everybody but should be based on a woman's individual risk of developing breast cancer."
