The information presented in this article does not necessarily reflect the current CAR standards on breast imaging. To consult the CAR guidelines on breast imaging consult car.ca.
Women with dense breasts have an increased risk of breast cancer, while dense breast tissue also decreases the sensitivity of mammography for detecting breast cancer.1,2 In Canada, different provinces have recently started notifying women of their breast density in a mammogram results letter, with BC becoming the first province to begin notifying women in October 2018. Many of these provincial screening programs now offer women with dense breasts a screening ultrasound or an annual mammogram.
The Dense Tissue and Early Breast Neoplasm Screening (DENSE) trial is a randomized, controlled trial that is investigating the use of MRI as a supplementary imaging modality in women with extremely dense breasts. While previous studies have demonstrated that MRI can increase the sensitivity of breast cancer detection compared to mammography, the primary objective of the DENSE trial is to investigate whether MRI can improve early detection and reduce interval cancer rate.
Results from the first screening round of the DENSE trial were published in the New England Journal of Medicine in November 2019.3 The study includes 40,373 women with extremely dense breasts and negative results on mammography. These women were randomized into groups of 8061 invited for supplemental screening with MRI and 32,312 assigned to mammography-only.
The invitation for supplemental screening with MRI was accepted by 4783 (59%) women. Of these participants who underwent MRI screening after a negative mammogram, MRI detected 16.5 cancers per 1000 screenings, with a biopsy rate of 62.7 per 1000 and a false positive rate of 79.8 per 1000 screenings.
In 2 years of follow-up after the first screening round, the key result of the DENSE trial is that MRI was shown to significantly reduce the interval cancer rate in women with extremely dense breasts. The interval cancer rate was 2.5 per 1000 women invited for supplemental screening with MRI versus 5.0 per 1000 women in the mammography-only group (p<0.001). For women in the MRI-invitation group who actually underwent MRI screening, the interval cancer rate was 0.8 per 1000 women.
While the November publication summarized results from the first round of screening and two years of follow-up, the study is continuing for three biennial screening rounds. Additionally, further investigation of the DENSE trial data is underway in a simulation study to evaluate reduction in mortality, extent of overdiagnosis, as well as effects on cost and quality of life. The data will also be used to validate the use of abbreviated protocols, which may serve as an important strategy to improve MRI access for breast screening.
[References]
- McCormack VA, dos Santos Silva I. Cancer Epidemiol Biomark Prev 2006; 15(6):1159-1169
- Wanders JO et al. Breast Cancer Res Treat 2017; 162(1):95-103
- Bakker et al. N Engl J Med 2019; 381(22):2091-2102