Prospective screening study of 0.5 Tesla dedicated magnetic resonance imaging for the detection of breast cancer in young, high-risk women

Abstract

Background: Evidence-based screening guidelines are needed for women under 40 with a family history of breast cancer, a BRCA1 or BRCA2 mutation, or other risk factors. An accurate assessment of breast cancer risk is required to balance the benefits and risks of surveillance, yet published studies have used narrow risk assessment schemata for enrollment. Breast density limits the sensitivity of film-screen mammography but is not thought to pose a limitation to MRI, however the utility of MRI surveillance has not been specifically examined before in women with dense breasts. Also, all MRI surveillance studies yet reported have used high strength magnets that may not be practical for dedicated imaging in many breast centers. Medium strength 0.5 Tesla MRI may provide an alternative economic option for surveillance.

Methods: We conducted a prospective, nonrandomized pilot study of 30 women age 25-49 years with dense breasts evaluating the addition of 0.5 Tesla MRI to conventional screening. All participants had a high quantitative breast cancer risk, defined as > or = 3.5% over the next 5 years per the Gail or BRCAPRO models, and/or a known BRCA1 or BRCA2 germline mutation.

Results: The average age at enrollment was 41.4 years and the average 5-year risk was 4.8%. Twenty-two subjects had BIRADS category 1 or 2 breast MRIs (negative or probably benign), whereas no category 4 or 5 MRIs (possibly or probably malignant) were observed. Eight subjects had BIRADS 3 results, identifying lesions that were "probably benign", yet prompting further evaluation. One of these subjects was diagnosed with a stage T1aN0M0 invasive ductal carcinoma, and later determined to be a BRCA1 mutation carrier.

Conclusion: Using medium-strength MRI we were able to detect 1 early breast tumor that was mammographically undetectable among 30 young high-risk women with dense breasts. These results support the concept that breast MRI can enhance surveillance for young high-risk women with dense breasts, and further suggest that a medium-strength instrument is sufficient for this application. For the first time, we demonstrate the use of quantitative breast cancer risk assessment via a combination of the Gail and BRCAPRO models for enrollment in a screening trial.

Figure 1

Figure 2

Imaging of subject 006. A) Subject 006 pre-MRI mammogram demonstrating heterogeneously dense breast tissue. There is no evidence of a cancerous lesion. B) Pre-contrast MR image showing an approximately 1.5 cm, smooth, round lesion in the right breast just above the nipple level medial and close to the chest wall (arrowhead). Core biopsy of this lesion demonstrated benign pathology, specifically, fibrosis with focal ductal epithelial hyperplasia [44]. C) Post-contrast MR images showing a small (approximately 1 cm), round, well-delineated enhancing mass (arrow) in the left breast at the 1:00 position. This mass was seen on both the initial delay after contrast injection (left) and the delayed contrast enhanced subtraction images (right). Core biopsy of this lesion indicated infiltrating ductal carcinoma, which was confirmed after removal via modified radical mastectomy [44].