Is MRI Better Than Mammography?
European Studies Indicate High-Risk Women Can Benefit From MRI Screening for Breast Cancer
June 2, 2003 (Chicago) -- In a pair of European studies comparing methods for breast cancer screening, magnetic resonance imaging was better than mammography for identifying early-stage cancers in women at high risk for breast cancer. But American experts say it is too soon to recommend switching from the recommended mammography method to MRI.
MRI screening can detect very tiny tumors, which makes it an attractive screening option for women who have the genetic mutations that raise the risk of breast cancer, says Mark E. Robson, MD, an assistant attending physician at Memorial Sloan-Kettering Cancer Center in New York. But unfortunately, MRI is so good at detecting tiny irregularities that it also finds many benign growths -- findings that may lead to more tests, increased anxiety, and, sometimes, even unnecessary surgery, he says.
Robson discussed MRI for breast cancer screening at a news conference at the American Society of Clinical Oncology annual meeting.
Robson presented results from a U.S. study of 54 women with either of the genetic mutations, known as BRCA1 and BRCA2, who underwent 97 MRI exams for breast cancer screening. The women were screened between July 1998 and April 2003. During the study period, two women developed precancerous breast lesions, says Robson. But more than 36% of the MRI screenings were judged inconclusive, and follow-up MRI was recommended. Eventually, because of the false-positive results of the screening, MRI biopsies were recommended.
The situation is much different in Europe, says Christiane K. Kuhl, MD, of the University of Bonn in Germany. She says a study of MRI at her center indicated the false-positive rate is "actually very low," but she says this might reflect the expertise of the investigators. "At our center we do more than 2,000 MRI exams a year. ... Accuracy builds with experience."
Kuhl's team followed 45 high-risk women for five years. During that time, "MRI detected 51 cancers and missed two," she says. But the detection rate for mammography was just 43% and for ultrasound was 47%, she says.
Moreover, she says that for women who have BRCA1 or BRCA2 mutations, MRI might be a safer way to screen. She says that these women start mammography screening while they are still in their 30s, which means many more years of exposure to radiation from mammography. Since their genetic defect impairs the ability to repair cell damage, the long-term radiation exposure could increase breast cancer risk.
Robson points out, however, that women who have the breast cancer gene usually have only one mutated copy. This leaves them with one "good" gene, "which is enough to repair the damage caused by low-dose radiation."
Jan G. M. Klijn, MD, PhD, of the Erasmus Medical Center at the University Medical Center in Rotterdam, Netherlands, agrees with Kuhl's assessment of the benefits of MRI.