MRI Versus Mammography for Breast Cancer Screening in Dense Breasts: Systematic Review

Abstract

Introduction: Dense breast tissue reduces mammography sensitivity. Supplemental MRI detects additional cancers but increases false positives. Comparative outcomes in average-risk women with dense breasts are needed.
Methods: Systematic review of 6 RCTs (n=8,204) comparing MRI plus mammography versus mammography alone in women with dense breasts (BI-RADS C/D) and average risk (no BRCA, strong family history). Primary outcome: invasive breast cancer detection rate per 1,000 screens. Secondary: interval cancer rate, false-positive biopsy rate.
Results: MRI added 5.2 additional invasive cancers per 1,000 screens (95% CI 4.1–6.3) compared to mammography alone. Interval cancer rate dropped from 2.8 to 0.7 per 1,000 (p=0.001). False-positive biopsy rate increased from 8.3% to 15.6% (NNH=13.7). No significant difference in advanced cancer stage at diagnosis.
Discussion: MRI detects more small, node-negative cancers but at cost of many benign biopsies. Long-term mortality reduction is unproven.
Conclusion: MRI screening in dense breasts doubles cancer detection but also false positives. Shared decision-making is essential.