New research suggests that abbreviated magnetic resonance imaging (AB-MR) may enhance early detection of breast cancer in women with dense breasts and average breast cancer risk.
For the retrospective study, recently published in the American Journal of Roentgenology, researchers evaluated AB-MR in supplemental breast cancer screening in 2007 women (mean age of 56.7 at baseline) with dense breasts and at otherwise average risk for developing breast cancer. The total number of AB-MR exams included 2,007 baseline exams and 578 subsequent round screenings.
Overall, the researchers noted that AB-MR led to the detection of 45 breast cancers in 2,585 examinations, resulting in a cancer detection rate (CDR) of 17.4 per 1000. The study authors also noted a positive predictive value 2 (PPV2), the fraction of breast cancers diagnosed among recommended biopsies, of 22.2 percent, and a PPV3, fraction of breast cancers diagnosed among biopsies performed, of 26.9 percent.
“The findings support the utility of AB-MR for both baseline and subsequent screening rounds in individuals with dense breasts,” wrote lead study author Christine E. Edmonds, M.D., an assistant professor of radiology at the Hospital of the University of Pennsylvania, and colleagues.
Baseline assessments of BI-RADS categories 4-5 led to the diagnosis of 38 malignancies with a corresponding 18.9 per 1000 CDR as well as a 21.3 percent PPV2 and a 26.6 percent PPV3, according to the study findings. For the 25 subsequent-round AB-MR exams, researchers noted detection of seven malignant cases for a CDR of 12.1 and pointed out a 28 percent PPV2 and a 29.2 percent PPV3.
The study authors also found that AB-MR had an abnormal interpretation rate (AIR), the combined frequency of BI-RADS categories 3-5, of 17.4 percent for baseline exams in comparison to 7.8 percent for subsequent-round exams.
“The reduction in AIR on subsequent-round AB-MR examinations without a significant change in PPV is clinically important. A primary criticism of screening MRI, both in high-risk populations and in individuals with dense breasts, is the examination’s high AIR with associated limited specificity, leading to high frequencies of false-positive follow-up MRI examinations and biopsies that are in turn associated with additional costs and patient morbidity,” emphasized Edmonds and colleagues.
For 1,527 baseline AB-MR exams with one year of follow-up, researchers noted a 96.7 percent sensitivity, which decreased to 75 percent for 367 subsequent-round exams with one-year follow-up. The study authors also noted a 93.2 overall specificity rate as well as similar specificity between subsequent-round AB-MR exams (97.2 percent) and baseline exams (92.3 percent).
Three Key Takeaways
1. High cancer detection rate (CDR). Abbreviated magnetic resonance imaging (AB-MR) demonstrated a cancer detection rate of 17.4 per 1000 in women with dense breasts and average breast cancer risk.
2. Abnormal interpretation rate (AIR) and specificity. The abnormal interpretation rate (AIR) was significantly lower in subsequent-round exams (7.8 percent) compared to baseline exams (17.4 percent), indicating improved specificity over time. Additionally, AB-MR showed high overall specificity (93.2 percent), with even higher specificity in subsequent exams (97.2 percent), suggesting reduced false-positive rates in follow-up screenings.
3. Preliminary evidence for safe intervals between AB-MR exams in women with dense breasts. Based on the study findings, the authors suggested that a 22-month interval may be safe but emphasized that further research is needed.
The study authors also pointed out that all diagnosed malignancies in the study involved stage 0 or stage 1 cancers. For six of the seven node-negative cancers detected in subsequent-round exams, the researchers said there was at least a 666-day interval between the initial negative AB-MR exam and the follow-up exam.
“The findings suggest that an AB-MR supplemental screening interval of at least (two) years may be safe in individuals with dense breasts but without otherwise elevated risk of breast cancer,” added Edmonds and colleagues, who cautioned that additional studies are necessary to clarify the timing of screening intervals.
(Editor’s note: For related content, see “Leading Breast Radiologists Discuss the USPSTF Breast Cancer Screening Recommendations,” “Breast MRI and Dense Breasts: A Closer Look at Early Findings from a New Prospective Trial” and “Five Takeaways from New Breast MRI Literature Review.”)
In regard to study limitations, the authors acknowledge that the study doesn’t provide direct evidence of the impact of abbreviated MRI in reducing medical treatments and extensive surgical procedures. It also doesn’t address the impact of abbreviated MRI on long-term outcomes, according to the researchers. The study authors also conceded a lack of racial diversity in the cohort and a potential bias with cancer detection rates from subsequent round abbreviated MRI exams that were performed in higher age groups.
