A randomized clinical trial reports that for women with extremely dense breasts, supplemental screening with magnetic resonance imaging (MRI) can reduce the incidence of interval breast cancers, those detected within 12 months of a mammography in which findings are considered normal.
Extremely dense breast tissue increases the risk of breast cancer, but it also increases the chances that cancer will be missed on a mammogram. While federal law requires the reporting of breast density in mammography results, US-based guidelines do not recommend supplemental imaging for women with dense breasts. Because supplemental imaging increases cancer detection rates in women with dense breast tissue, the Dense Tissue and Early Breast Neoplasm Screening (DENSE) trial sought to study the effect of MRI screening on the incidence of interval cancers for women with extremely dense breasts.
The DENSE trial, results of which have now been published in The New England Journal of Medicine, enrolled 40,373 women between the ages of 50 and 75 with extremely dense breast tissue and normal mammography screening results. Patients were randomized in a 1:4 ratio to receive either an invitation to a supplemental MRI (8,061 patients) or a mammography only (32,312 patients), for a primary end point of the between-group difference in the incidence of interval cancers over a two-year screening period.
Among the women in the MRI invitation group, 59% of whom chose to undergo the offered MRI, the interval cancer rate was 2.5 per 1,000 screenings, compared with 5.0 per 1,000 in the mammography-only group, resulting in a between-group difference of 2.5 per 1,000 screenings. Twenty interval cancers were diagnosed in the MRI invitation group; however, all but 4 of these occurred in the women who opted not to undergo MRI screening. Among the women who did opt to undergo MRI screening, the MRI cancer detection rate was 16.5 per 1,000 screenings, with positive predictive values of 17.4% for recall for additional testing and 26.3% for biopsy. The false positive rate was 79.8 per 1,000 screenings. Of the women who received MRI screening, 0.1% experienced an adverse event of any grade during or immediately following the screening.
"We found that supplemental screening with MRI in women with extremely dense breast tissue resulted in the diagnosis of significantly fewer interval cancers than the use of mammography alone," conclude the researchers in their publication, led by first author Marije F. Bakker, PhD, Assistant Professor of Epidemiology in the cancer research program of the Julius Center for Health Sciences and Primary Care of University Medical Center (UMC) Utrecht in Utrecht, the Netherlands. "The data from incident screening rounds and longer follow-up are needed in combination with simulation studies to assess the effect on the rate of advanced cancers and, eventually, on mortality."
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