Diffusion-Weighted MRI Reduces Number of Breast Biopsies

Diffusion-weighted imaging, which uses water diffusion measurements, performed with MRI for breast cancer screening may reduce the number of preventable breast biopsies, according to a study published online in the journal Radiology.

The increasing use of dynamic contrast-enhanced MRI (DCE-MRI) for breast cancer screening has resulted in a substantial number of false-positive findings. These false positives often resulted in women having to undergo unnecessary breast biopsies. Researchers found that the introduction of diffusion-weighted imaging (DWI) to DCE-MRI reduces the incidence of false-positives and the procedure does not require any additional contrast or hardware. Further, it only adds a few extra minutes to the exam.

“DWI has been used mostly in neurological applications, but it’s been studied more recently in breast imaging,” said Savannah C. Partridge, PhD, a research associate professor at the University of Washington, Seattle Cancer Care Alliance.

Researchers evaluated 175 non-malignant breast lesions in 165 women to assess the DWI in conjunction with MRI in distinguishing between benign and malignant breast tumors. The DWI calculates the apparent diffusion coefficient (ADC), a measure of how water moves through tissues.

Normal breast tissue has a high ADC because water moves through it relatively freely, while most cancers have a lower ADC because the cells are more tightly packed, restricting water movement. Based on ADC values above a previously determined diagnostic threshold, DWI successfully characterized 81 lesions (46 percent) that had been falsely identified as on DCE-MRI as benign.

The most prevalent lesion subtypes with mean ADCs above the threshold were fibroadenoma, focal fibrosis, normal tissue, apocrine metaplasia, usual ductal hyperplasia, and inflammation.
Atypical ductal hyperplasia was the most common lesion subtype with ADC below the threshold. High-risk lesions (atypical ductal hyperplasia and lobular neoplasia) showed significantly lower ADCs than other benign lesions and were the most common lesions with ADCs below the threshold.

“We were excited to see the number of false positives that could be reduced through this approach,” said Partridge in a press release. “DWI gives us extra microstructural information to distinguish among lesions. We can use ADC values to draw a cutoff above which we might not need to do a biopsy.”