Preliminary Results Suggest AB-MR Detects Breast Cancers that 3-D Mammograms May Miss

Preliminary results from the first clinical implementation of abbreviated breast magnetic resonance imaging (AB-MR) as a supplemental screening test in women with dense breasts found that AB-MR shows an increase in cancer detection over digital breast tomosynthesis (DBT or 3-D mammography) screening with positive predictive values (PPVs) that are in line with well-established benchmarks.¹

However, more data from additional sites with diverse screening populations and readers are necessary to determine the reproducibility of these single-institution results. Of note, this study was approved by the institutional review board and is Health Insurance Portability and Accountability Act compliant.

“As technology evolves, imaging is including more functional assessments of vascularity and biology. Mammography, even with the technical advances gained with transitions from film-screen to digital mammography and now to DBT, remains an anatomy-based examination with the masking effect of dense breast tissue decreasing cancer detection,” the authors wrote. “Breast cancer recruits neovascularity to maintain growth, and vascular-based imaging studies, such as AB-MR, leverage this key feature, especially in higher-grade malignancies.”

This retrospective review, published in the Journal of Clinical Oncology, included women who were imaged between January 1, 2016 and February 28, 2019. On a 1.5 Tesla magnet, the imaging protocol consisted of 3 sequences, including short-TI inversion recovery (STIR), precontrast, and postcontrast.

Of a total of 511 prevalent rounds of AB-MR examinations conducted, 36 women were excluded from the analysis. Importantly, the remaining 475 asymptomatic women with dense breasts had negative/benign DBT examinations before the AB-MR.

Overall, there were 420 of 475 (88.4%) benign/negative examinations, 13 of 475 (2.7%) follow-up recommendations, and 42 biopsy recommendations. Moreover, 39 biopsies were completed, which resulted in 12 (30.8%) malignancies in 12 women, including 7 invasive carcinomas and 5 ductal carcinoma in situ. In addition, 1 patient was diagnosed with invasive ductal carcinoma at the time of 6-month follow-up.

The cancer detection rate (CDR) was 27.4 per 1000 (13 of 475; 95% CI, 16.1-46.3). Notably, the size of invasive carcinomas ranged from 0.6-1.0 cm (mean, 0.5 cm). The PPV2 was 28.6%, and PPV3 was 30.8%.

Notably, PPV2 was the calculated using the number of cancers divided by the total number of biopsy recommendations (BI-RADS 4 and 5). PPV3 was calculated using the number of cancers divided by the total number of biopsies performed (BI-RADS 4 and 5).

Of the 7 women who underwent surgical evaluation of the axilla, 0 patients were found to have positive nodes. Further, there were no interval cancers at 1-year follow-up.

“Mammogram is the best tool we have to detect breast cancer, but it’s not perfect. In women with fatty tissue, we can very easily detect cancer. But in women with very dense breasts, the sensitivity can be low as 30%,” Susan Weinstein, MD, an associate professor of Radiology at Penn Medicine, said in a press release.² “We need to start thinking about how to better screen women with dense breasts, and AB-MR is an effective and feasible option.”

Of note, the current mammographic screening recommendations for average-risk women do not differ based on breast density. For women with dense breasts, the American College of Radiology states that MR screening may be beneficial, though further research on the topic is warranted. However, the ongoing Women Informed to Screen Depending on Measures of risk (WISDOM) Study (NCT02620852) may offer some clarity regarding the age to initiate screening and the frequency of screening by assessing if risk-based screening, including the consideration of breast density, is noninferior to annual screening.

“As even more data comes out, there is going to be a lot of debate about how we should screen women with dense breasts, and how we should pay for it. It is important to keep in mind that, although we are detecting more cancers, we don’t know the long-term benefits, such as survival benefits,” Weinstein added. “With further research, we will have more information in the future.”

References:

1. Weinstein SP, Korhonen K, Cirelli C, et al. Abbreviated Breast Magnetic Resonance Imaging for Supplemental Screening of Women With Dense Breasts and Average Risk. Journal of Clinical Oncology. doi: 10.1200/JCO.19.02198

2. ‘Fast’ MRI Detects Breast Cancers that 3-D Mammograms May Miss [news release]. Philadelphia. Published October 27, 2020. Accessed November 11, 2020. https://www.pennmedicine.org/news/news-releases/2020/october/fast-mri-detects-breast-cancers-that-3d-mammograms-may-miss