Report from ASCO: Studies reveal pros and cons of breast MRI

MRI's changing status as an instrument for breast cancer diagnosis and evaluation was apparent last month at the 2008 American Society of Clinical Oncology meeting. One study suggested that MR's growing popularity for treatment planning may had led to more mastectomies, and another trial added to growing evidence about its ability to identify metastatic lymph nodes.

The mastectomy findings arose from Fox Chase Cancer Center in Philadelphia. Lead author Dr. Richard Bleicher, codirector of Fox Chase's breast surgery fellowship program, reported that women who received an MRI had an 80% higher chance of having a mastectomy rather than a breast-conserving lumpectomy. The findings were drawn from the medical records of 577 breast cancer patients, 130 of whom had MRIs prior to treatment.

Bleicher believes the high number of false-positive findings associated with MRI may be leading to unnecessary breast removal.

"Rather than have a biopsy to see if the MRI findings are real, women and their doctors may choose mastectomy out of an abundance of caution," he said in an interview.

While some women will have cancer detectible only with MRI, Bleicher has seen an equivalent survival rate for patients who had mastectomies and patients treated with breast conservation and radiation. Bleicher and colleagues also found that MRI made no difference in giving surgeons a clearer picture of positive margins.

"Our study doesn't change the American Cancer Society's recommendation for use of MRI," he said. "MRI just shouldn't be used as a knee-jerk response to breast cancer."

The chance that MRI provides meaningful results depends on the baseline characteristics of the patient, according to Dr. Allison Kurian, an assistant professor of medicine and of health research and policy in the divisions of oncology and epidemiology at Stanford University School of Medicine.

"The question is how high risk is this patient to have another area of cancer somewhere that's getting missed by the mammogram? Screening with MRI only gets done in women who are above a certain risk because the feeling is that's the only time it's worthwhile to find extra [cancer]," she said.

Dr. Elizabeth Morris, director of breast MRI at Memorial Sloan-Kettering Cancer Center in New York City, agrees that breast MR should not be used as a knee-jerk method on anyone with cancer. She believes, however, that it should be part of a routine patient evaluation for treatment.

Experience has taught Morris that MRI delineates the extent of the disease better than alternative imaging modalities. It provides an optimal view of the contralateral breast and, with some frequency, characterizes contralateral cancers when a known cancer is in the ipsilateral breast.

Improved MR spectroscopy and other technical advances are helping cut down on the incidence of false positives with breast MR, but more research is needed to refine its role in breast cancer diagnosis, Morris said.

While Bleicher's study suggests that breast MRI may be leading to more mastectomies, a separate study from the Seattle Cancer Care Alliance and the University of Washington Medical Center also presented at the ASCO meeting found that breast MRI can be an alternative to exploratory surgery in helping women whose breast cancer has spread to their lymph nodes determine if they need radiation to treat the disease.

The retrospective study of 167 patients who underwent radiation therapy for invasive breast cancer after surgical staging of their tumors determined that the tumors' physiological information shown on MR scans correlated with surgically based findings of cancer having spread to lymph nodes. This suggests that breast MRI could help determine if women scheduled to undergo surgery will later need radiation therapy, according to lead author Dr. Christopher Loiselle, a resident in the radiation oncology department at Washington.

"When you give chemotherapy first, and then perform the surgery to remove the cancer and sample the lymph nodes, you reduce your ability to know whether there was cancer in the axillary (underarm) lymph nodes before the patient was treated with chemotherapy," Loiselle said. "This raises the question: Is there another way to stage those lymph nodes? Our study showed that tumor characteristics as seen on an MR scan may be the answer."

For more information from the Diagnostic Imaging website:

Breast MRI before irradiation zeros in on remote multifocal disease

Preoperative breast imaging guides surgical management

MRI breast cancer staging proves benefits, shortcomings