Utility of Diffusion Weighted Imaging to Decrease Unnecessary Biopsies Prompted by Breast MRI: A Trial of the ECOG-ACRIN Cancer Research Group (A6702)

Purpose: Conventional breast MRI is highly sensitive for cancer detection but prompts some false-positives. We performed a prospective, multicenter study to determine whether apparent diffusion coefficients (ADCs) from diffusion weighted imaging (DWI) can decrease MRI false-positives. Experimental Design: 107 women with MRI-detected BI-RADS 3, 4, or 5 lesions were enrolled from March 2014 to April 2015. ADCs were measured both centrally and at participating sites. Receiver operating characteristic (ROC) analysis was employed to assess diagnostic performance of centrally-measured ADCs and identify optimal ADC thresholds to reduce unnecessary biopsies. Lesion reference standard was based on either definitive biopsy result or at least 337 days of follow-up after the initial MRI procedure. Results: Of 107 women enrolled, 67 patients (median age 49, range 24-75 years) with 81 lesions with confirmed reference standard (28 malignant, 53 benign) and evaluable DWI were analyzed. 67/81 lesions were BI-RADS 4 (n=63) or 5 (n=4) and recommended for biopsy. Malignancies exhibited lower mean centrally-measured ADCs (mm²/s) than benign lesions (1.21x10^-3 vs.1.47x10^-3, p<0.0001, area under ROC curve=0.75, 95% confidence interval [CI] 0.65-0.84). In centralized analysis, application of an ADC threshold (1.53x10^-3 mm²/s) lowered the biopsy rate by 20.9% (14/67; 95% CI 11.2-31.2%) without affecting sensitivity. Application of a more conservative threshold (1.68x10^-3mm²/s) to site-derived ADCs reduced the biopsy rate by 26.2%(16/61) but missed three cancers. Conclusion: DWI can re-classify a substantial fraction of suspicious breast MRI findings as benign and thereby decrease unnecessary biopsies. ADC thresholds identified in this trial should be validated in future Phase III studies.

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