Audits of breast MRI performance should separate screening from diagnostic

The cancer detection rate was significantly lower for breast MRI screenings than for diagnostic MRIs, according to a study published in the September issue of the Journal of the American College of Radiology.

The findings demonstrated that breast MRI performance measures vary significantly when stratified by screening versus diagnostic indications, according to authors Bethany L. Niell, MD, PhD, of Massachusetts General Hospital in Boston, and colleagues.

The study included 2,444 examinations, 1,313 for screening and 1,131 for diagnostic indications. The breast MRI BI-RADS assessment was obtained from medical records for each one of the exams. Benign or malignant outcome was determined for each patient with a breast MRI examination done during the study. Outcomes were based on biopsy results, imaging follow-up, or clinical surveillance, performed within one year of the breast MRI examination.

Results showed that the cancer detection rates were 14 per 1,000 screening breast MRI examinations, compared with 47 per 1,000 diagnostic MRI examinations. The positive predictive value was also lower for screening compared with diagnostic MRIs.

Breast diagnostic MRIs accounted for 69 percent of the lesions recommended for biopsy, including 77 percent (61 of 79) of the biopsies resulting in diagnoses of malignancy. The majority of MRI-detected malignancies were invasive carcinomas.

Niell and colleagues suggested that performance benchmarks for breast MRI account for the variance in detection rates.

“Medical audits for breast MRI should calculate performance measures for screening and diagnostic breast MRI separately, as recommended for mammography,” they wrote.