MRI detects cancers missed by mammography in breast cancer patients

Jun 5 2007

A unique examination of one treatment center's use of magnetic resonance imaging (MRI) in new breast cancer patients has found MRI to be superior to mammography in finding additional tumors in a breast in which cancer has already been diagnosed, and in detecting new tumors in a patient's supposedly healthy breast.

Two studies conducted by oncologists from Mayo Clinic (http://cancercenter.mayo.edu/) in Jacksonville, Fla., and presented at the annual meeting of the American Society of Clinical Oncology (http://www.asco.org/portal/site/ASCO) (ASCO), also revealed distinct patterns between MRI-detected ipsilateral tumors (cancer in the affected breast) and contralateral tumors (cancer in the unaffected breast) that could guide use of the screening technology, researchers say.

"These results prove that MRI can detect tumors missed by traditional exams, and can be vital in helping women choose the right course of treatment for their breast cancer," says Mayo radiation oncologist Laura Vallow, M.D. She and other radiation oncologists at the Multidisciplinary Breast Clinic (http://www.mayoclinic.org/breastcancerprogram-jax/) in Jacksonville scan both breasts of all newly diagnosed breast cancer patients with mammograms and MRI and so have been able to compare results from both screening techniques in hundreds of women.

In their study comparing MRI and mammography in detection of ipsilateral breast cancer -- the first such study of its kind in the nation --the researchers found that MRI detected tumors missed by mammography in 16 percent of 390 patients. Women with MRI-detected ipsilateral tumors tended to be younger or they had a primary breast tumor that was at least 1 centimeter in size. The primary tumors also belonged to many different breast cancer subtypes, and newly diagnosed tumors were different from the primary tumor in 29 percent of patients.

"This is an important finding because breast cancer tends to be more aggressive when diagnosed in younger women," says Dr. Vallow, the study's lead investigator. "This suggests that younger women who want breast-conserving surgery to treat newly diagnosed cancer may benefit from an MRI scan of the entire breast."

The second study, which compared MRI versus mammography in detection of contralateral breast cancer, found that MRI detected tumors missed by mammograms in 3.2 percent of 401 women. Some women participated in both studies, and in a few cases, MRI found tumors in both breasts that were not found by mammography.

Patients with MRI-detected tumors were more likely to be postmenopausal, and to have a common type of tumor, one classified as estrogen receptor (ER)-positive, says the contralateral breast study's lead investigator, oncology resident Johnny Bernard Jr., M.D., who works with Dr. Vallow. This result mirrors findings of a 969-patient study reported in April 2007 in the New England Journal of Medicine (http://content.nejm.org/) (NEJM) which concluded that MRI detected contralateral breast tumors in 3.1 percent of patients that had been missed by mammography. Data on 65 Mayo patients were part of the NEJM study.

Detecting contralateral breast cancer before a newly diagnosed patient is treated is important, says Dr. Bernard. "Patients can have treatment for both breast cancers simultaneously rather than the physical and psychological trauma of having a contralateral cancer detected years later," he says. "Furthermore, treatment recommendations by the physician may be affected by the finding of a contralateral cancer, as well as patient preferences for one treatment versus another, such as for mastectomy versus breast-conserving surgery.

"Patients with a diagnosis of breast cancer are considered high risk and therefore we contend that these patients should have a screening MRI to further evaluate the extent of ipsilateral disease and also to evaluate the contralateral breast," says Dr. Bernard.

"The combined results of these studies validate what we have already seen in our clinic, and that is that MRI breast cancer screening is quickly becoming an indispensable tool," says Dr. Vallow. "studies like these are needed to pave the way toward greater use of MRI breast cancer screening in newly diagnosed patients."

However, Dr. Vallow acknowledges that MRI scans need to be faster, cheaper, more accessible, and uniform across institutions," before it can be widely used, and cautions that cancer centers that use MRI also need to be able to perform MRI-guided biopsy of the suspected tumor, if necessary. "There is huge variation in how clinics conduct breast MRI screenings, because there is no quality control at the moment," she says. "Patients at centers that don"T offer MRI-guided biopsy can end up having mastectomies because physicians there have no way to investigate the findings seen on the scan."

New guidelines, issued in April by the American Cancer Society (http://www.cancer.org/docroot/home/index.asp), recommend that women who are at high risk of developing breast cancer receive both annual MRI and mammography scans starting at age 30.