MRI Detects Early Breast Cancer Cells
Study Shows MRI Screening Has High Detection Rate of Precancerous Cells
The Problems With MRI continued...
But false positive results remain the biggest impediment to the use of breast MRI in the screening of average-risk women, Saslow says.
The imaging technique is so sensitive that it finds many suspicious growths that turn out not to be breast cancer (false positive), resulting in many unnecessary biopsies.
In the roughly 2% of American women who are considered to be at high risk for breast cancer, the benefits of screening MRI outweigh these risks, but Saslow says this is not true for most other women.
"For average-risk women, the harms of MRI outweigh the risks," she says. "In addition, there have been no studies, including the current one, which assessed MRI screening of women who were not at high risk."
Roughly one in six (29 of 167) of detected DCIS cases in the study by Kuhl and colleagues occurred among average-risk women. The rest, Saslow points out, occurred in women with a known elevated breast cancer risk.
Ninety-three were referred for MRI because of abnormal mammograms, 18 had been treated for breast cancer, and eight had family history of the disease.
"The women in the study were not representative of the population at large, so it doesn't tell us much about the use of MRI in average-risk women," she says.
The Promise of MRI
About 20% of breast cancers now detected are confined to the milk ducts, compared to just 2% prior to the widespread use of mammography.
In an editorial accompanying the German study, radiology professor Carla Boetes, MD, PhD, of Radboud University in The Netherlands, writes that while mammography had dramatically improved the detection of these very early breast cancers, wider use of screening MRI might have an even greater impact.
"That only 20% of tumors detected through screening are pure DCIS is disappointing, when one keeps in mind that most breast tumors probably evolve from DCIS," she writes. "The observation that MRI detects many DCIS lesions that go unnoticed on mammography implies that some invasive carcinomas can be prevented by timely intervention on the basis of MRI findings."