MRI and Mammography Combined are Effective in Detecting Breast Cancer in Women at High Risk

Chiarelli et al in their JCO article report on Ontario’s Breast Screening Program of women age 30 to 69 years at high risk for breast cancer with annual magnetic resonance imaging (MRI) and digital mammography.

The study cohort consisted of 2,359 women. The following criteria were used to determine eligibility: known BRCA1, BRCA2 mutation, or other gene predisposing to a markedly increased risk of breast cancer, untested first-degree relative of a gene mutation carrier, family history consistent with hereditary breast cancer syndrome and estimated personal lifetime breast cancer risk of 25% or higher, or radiation therapy to the chest before age 30 years.

Digital mammograms were performed with standard craniocaudal and mediolateral oblique projections.  The minimum MRI standards were 1.5 Tesla units, gadolinium injection (0.1 to 0.2 mmol/kg) and a dedicated breast coil. Both breasts were imaged in axial and sagittal planes.  Most of the eligible women (90.7%) had their MRI within a month from their mammograms.  Of the 2,359 eligible women 2,290 were screened.  Of the women screened 2,157 had an MRI and were included in the study as women who had only a mammogram were excluded.

The recall rate of 15% was significantly higher among women who had abnormal MRI alone compared with 6.4% when mammogram alone was used.  Of the 35 breast cancers detected (16.3 per 1,000), none were detected by mammography alone, while 23 (65.7%) were detected by MRI alone (10.7 per 1,000), and 25 (71%) were detected among women who were known gene mutation carriers (30.8 per 1,000). The positive predictive value of 12.4% for detection was highest when findings from mammogram and MRI were combined.  Overall, the cancer detection rate was significantly higher for invasive cancers (12.6 per 1,000) compared with DCIS (3.7 per 1,000). Cancer detection rates were higher among women age 50 years (23.3 per 1,000) compared with women younger than age 50 years (13.3 per 1,000) and significantly higher among those who were known gene mutation carriers (30.8 per 1,000) compared with those with a family history plus an estimated lifetime cancer risk of 25% (6.9 per 1,000).

The authors conclude that screening with annual MRI combined with mammography is effective and could be implemented into an organized breast screening program for women at high risk for breast cancer as mammograms alone failed to detect early breast cancers. 

An editorial by Dr. Wendie Berg with comments on this topic was published by the Journal of Clinical Oncology.