DW MR may help reduce preventable breast biopsies
Diffusion-weighted (DW) breast MR imaging may help differentiate high-risk breast lesions that require biopsy from other nonmalignant subtypes, according to a study published online Oct. 2 in Radiology.

Although dynamic contrast-enhanced MRI has been employed in screening high-risk women, follow-up and problem solving of suspicious lesions, it results in a substantial rate of false-positive results that lead to biopsy.

“DW imaging is a short, non-contrast-enhanced MR imaging sequence that has strong potential to increase specificity as an adjunct to conventional breast MR imaging protocols,” wrote Sana Parsian, MD, from the department of radiology at University of Washington School of Medicine in Seattle and the Seattle Cancer Care Alliance, and colleagues.

Previous research has established that apparent diffusion coefficients (ADCs) obtained via DW imaging studies are significantly lower for breast carcinomas than for benign breast lesions or normal tissue. Parsian and colleagues sought to characterize ADCs for nonmalignant subtypes representative of false positives at biopsy. They analyzed which subtypes fell below a previously proposed ADC threshold of 1.81 x 10-3 mm2/second.

The study was comprised of 175 nonmalignant lesions in 161 women. Radiologists prospectively recorded lesion characteristics based on dynamic contrast-enhanced MR image data acquired from October 2005 through December 2008. Researchers trained in quantitative analysis of breast MR images retrospectively calculated ADCs for each lesion.

Mean ADCs for the 28 high-risk lesions were significantly lower than those of the 147 benign lesions, according to Parsian et al.

A total of 46 percent of the lesions exhibited ADCs above the previously established threshold. The most common subtypes in this group were fibroadenoma, adenosis and focal fibrosis. However, fibroadenosis and adenosis also appeared in the group of most common subtypes below the threshold. In addition to the overlap issue, implementation of a diagnostic threshold faces the challenge of malignant lesions with high ADCs and nonmalignant lesions with low ADCs.

Parsian and colleagues noted that substantial savings in time and patient discomfort could have resulted if breast biopsy had been avoided in the 81 women with ADCs above the threshold. However, although applying a lower threshold could have spared additional biopsies it might have increased the false-negatives.

The researchers called for large multicenter trials to further study the added value of DW imaging and pointed out, “the decision to avoid biopsy for lesions that were positive at dynamic contrast-enhanced MR imaging and negative at DW imaging cannot be entirely supported on the basis of our study.”