From the Guidelines
The false positive rate for breast MRIs is approximately 8-17%, with a range of recalls for additional imaging, as evidenced by the study published in the Ca-A Cancer Journal for Clinicians 1.
Key Findings
- The study compared the rates of detection and follow-up tests for screening MRI and mammography in two screening studies, the Dutch and UK studies.
- The recall rates for MRI screening ranged from 8% to 17%, with biopsy rates ranging from 3% to 15% 1.
- The proportion of biopsies that are cancerous, or the positive predictive value, is around 20% to 40% 1.
Factors Contributing to False Positives
- Normal hormonal changes in breast tissue
- Benign conditions like fibroadenomas
- Technical factors related to the imaging process
- Patient characteristics, such as a low-suspicion lesion, which may contribute to a higher rate of benign biopsies 1
Implications
- The high false positive rate of breast MRI screening can lead to additional imaging, biopsies, and increased patient anxiety.
- The benefits of breast MRI screening, including its high sensitivity, must be weighed against the potential harms of false positive results, particularly in high-risk populations.
- As reported in the study, despite the high number of recalls, the rate of benign surgical biopsy per cancer detected was similar to that experienced in the population-based national breast screening service 1.
From the Research
False Positive Results in Breast MRI Scans
- The percentage of breast Magnetic Resonance Imaging (MRI) scans that yield false positive results is a significant concern in breast cancer screening 2.
- A study published in 2018 found that the positive predictive value (PPV) of breast MRI was 44.8%, indicating that approximately 55.2% of biopsies performed due to positive MRI findings were false positives 2.
- Another study published in 2005 reported that 69% of false positive MRI findings were due to variants of normal tissue, while 31% were due to benign masses 3.
- A 2021 study developed prediction models to reduce the rate of false positive screening MRI findings in women with extremely dense breasts, which could potentially prevent 45.5% of false positive recalls and 21.3% of benign biopsies 4.
- The likelihood of a false positive diagnosis, including atypias, was found to be twice as high in women undergoing biopsy for MRI findings (40%) as for those with mammography findings (18%) 2.
Comparison of False Positive and True Positive Findings
- A 2022 study compared the imaging characteristics of false positive and true positive findings on contrast-enhanced digital mammography, finding that true positive lesions were more likely to exhibit both a mammographic finding on low-energy images and a contrast finding on iodine images 5.
- A 2019 study investigated factors associated with false negative and false positive results in a computer-aided diagnostic system for ultrasound examinations of solid breast lesions, finding that larger lesions, the presence of lesion calcifications, and high degrees of vascularity were associated with false positive results 6.