A call for judicious use of diagnostic breast MRI

Current evidence does not support the routine use of breast MRI in women with newly diagnosed breast cancer, according to Monica Morrow, MD, chief of the breast service, department of surgery, at Memorial Sloan-Kettering Cancer Center.

“There can be absolutely no doubt that MRI finds cancer that is not found by physical exam, mammogram, or ultrasound,” said Dr. Morrow. “It has always been assumed that…the presence of cancer detected by MRI was in fact beneficial to the woman with breast cancer.”

Two potential benefits of breast MRI in the breast cancer population are improving patient selection for breast-conserving therapy (BCT), which might reduce rates of conversion to mastectomy, and better defining tumor extent, which might reduce the need for re-excision, she noted. But retrospective data show that the rate of positive margins does not differ between women who do and do not have breast MRI; moreover, the rate of mastectomy (12% vs 5%) is more than twice as high with MRI (Breast Cancer Res Treat online, September 21, 2008).

And data from the first prospective randomized trial of the role of MRI in women selected for BCT agree, showing no difference in six-month reoperation rates (SABCS 2008 abstract 51).

A third possible benefit of diagnostic breast MRI is synchronous identification of cancer in the contralateral breast, according to Dr. Morrow, who spoke during a plenary session at SABCS 2008. A study has argued against such benefit, however, finding that women who do and do not undergo breast MRI at diagnosis have an identical eight-year incidence of contralateral breast cancer of 6% (J Clin Oncol 26:386-391, 2008).

A fourth possible benefit of breast MRI in breast cancer patients is reducing the rate of local recurrence. But only about 5% of patients receiving systemic therapy have a recurrence within a decade, Dr. Morrow pointed out, “so the bar for improving that is set extremely high.” Indeed, after adjustment for potential confounders, the rate of local recurrence with a median follow up of about five years does not differ significantly between women (3% vs 4%) who do and do not have breast MRI (J Clin Oncol 26:386-391, 2008).