Breast MRI

Magnetic resonance imaging (MRI) has been shown to detect cancers not visible on mammograms, but has long been regarded to have disadvantages. For example, although it is 27-36% more sensitive, it is less specific than mammography. As a result, MRI studies will have more false positives (up to 5%), which may have undesirable financial and psychological costs. It is also a relatively expensive procedure, and one which requires the intravenous injection of a chemical agent to be effective. Proposed indications for using MRI for screening include:

• Strong family history of breast cancer

• Patients with BRCA-1 or BRCA-2 oncogene mutations

• Evaluation of women with breast implants

• History of previous lumpectomy or breast biopsy surgeries

• Axillary metastasis with an unknown primary tumor

• Very dense or scarred breast tissue

However, two studies published in 2007 demonstrated the strengths of MRI-based screening:

• In March 2007, an article published in the New England Journal of Medicine demonstrated that in 3.1% of patients with breast cancer, whose contralateral breast was clinically and mammographically tumor-free, MRI could detect breast cancer. Sensitivity for detection of breast cancer in this study was 91%, specificity 88%.

• In August 2007, an article published in The Lancet compared MRI breast cancer screening to conventional mammographic screening in 7,319 women. MRI screening was highly more sensitive (97% in the MRI group vs. 56% in the mammography group) in recognizing early high-grade Ductal Carcinoma in situ (DCIS), the most important precursor of invasive carcinoma. Despite the high sensitivity, MRI screening had a positive predictive value of 52%, which is totally accepted for cancer screening tests.The author of a comment published in the same issue of The Lancet concludes that "MRI outperforms mammography in tumour detection and diagnosis.
  

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