Breast cancer screening using MRI versus mammography associated with more biopsies but lower cancer yield

1. In women both with and without personal history of breast cancer (PHBC), screening MRI was associated with higher biopsy rates compared to mammography.

2. Screening MRI was also associated with lower rates of ductal carcinoma in situ (DCIS) and invasive cancer findings when compared to mammography.

Evidence Rating Level: 2 (Good)

Study Rundown: Screening breast magnetic resonance imaging (MRI) is used primarily as an adjunct to screening mammography for women at high risk for breast cancer. However, there is limited evidence on the possible harms and benefits of screening MRI in women with and without a personal history of breast cancer (PHBC). This study was an observational cohort study that used Breast Cancer Surveillance Consortium (BCSC) registries to compare the biopsy intensity and yield within 90 days of a breast MRI screening or digital mammography episode. Study results indicated that core and surgical biopsy rates doubled following MRI compared with mammography in women with PHBC, and was five times greater in women without PHBC. Furthermore, DCIS and invasive biopsy yield was lower following MRI versus mammography, with more common detection of high-risk benign lesions with MRI.

The large number of patients included in this study strengthens the conclusions. However, a randomized controlled study could allow conclusion of causality between the screening MRI versus mammography and subsequent biopsy risk and diagnosis. Further studies investigating the long-term implications of MRI versus mammography (i.e., cancer stage at diagnosis, morbidity and mortality, etc.) may shed additional light on the benefits and harms of screening MRI. However, these results alone have implications for clinical practice, and indicate that women should be informed about the higher likelihood of biopsy and the lower likelihood of clinically actionable findings following MRI. Furthermore, additional research identifying women who may have a higher benefit-to-harm ratio from MRI would be beneficial.

Click to read the study in JAMA Internal Medicine

Relevant Reading: American Cancer Society guidelines for breast screening with MRI as an adjunct to mammography.

In-Depth [retrospective cohort study]: This study examined a sample of 812 164 women in Breast Cancer Surveillance Consortium registries undergoing screening for breast cancer via mammography or MRI, and compares the biopsy intensity (surgical greater than core great than fine-needle aspiration) and yield (invasive cancer greater than DCIS greater than high-risk benign greater than benign) within 90 days of screening. Women were further stratified by personal history of breast cancer (PHBC). Age-adjusted core and surgical biopsy rates were 2 times greater following MRI vs. mammography in women with PHBC (57.1 vs. 23.6 per 1000 episodes, respectively), and 5 times greater in women without PHBC (84.7 vs. 14.9 per 1000 episodes, respectively). DCIS and invasive biopsy yield was lower in MRI (267.6, 95% CI, 208.0-337.8) vs. mammography (404.6, 95% CI, 381.2-428.8) in women with PHBC, and higher but without statistically significance in women without PHBC. A greater number of high-risk benign lesions were identified following MRI vs. mammography. Differences in biopsy rates and cancer yield could not be explained by differences in age or 5-year breast cancer risk.

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