Mammography, MRI Combined Best for High-Risk Screening Program

First-year results of a Canadian study show that annual MRI and mammography in a high-risk population can be effectively implemented into an organized screening program, and that the addition of MRI has important implications, particularly in women who are known breast cancer gene mutation carriers.

Specifically, results from the Ontario Breast Screening Program published in The Journal of Clinical Oncology, showed that all breast cancers detected were found either on MRI alone or in combination with mammography.

Anna M. Chiarelli, PhD, of Prevention and Cancer Control, Cancer Care Ontario, and colleagues, expanded the Ontario Breast Screening Program in July 2011 to screen women aged 30 to 69  at high risk for breast cancer with annual MRI and digital mammography. High-risk was categorized as having known BRCA1/2 or other gene mutations associated with breast cancer risk, untested first-degree relative with gene mutations, family history consistent with breast cancer syndrome, or radiation therapy to the chest before age 30.

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“The prospective collection of data on this large population of high-risk women will help resolve many of the yet unanswered questions about high-risk screening, including the need for mammography, the adequacy of annual MRI for women younger than age 40 (the age at which MRI may safely be discontinued), and the benefit of MRI for screening women with a history of chest radiation,” the researchers wrote.

First-year data included results from 2,207 women with initial screening examinations.

The researchers found that the recall rate was significantly higher among women who had abnormal MRI (15.1 percent) compared with abnormal mammogram alone (6.4 percent) or abnormal mammogram and MRI (4.7 percent).

The researchers wrote that “it is expected that the recall rate will likely be significantly lower in future rounds of screening when there is a baseline MRI for comparison and when the centers gain more experience.”

Of the 35 breast cancers detected, none were found by mammogram alone. Twenty-three cancers were detected by MRI alone and 12 were detected using both mammogram and MRI. Twenty-five of the breast cancers were detected among women who were known gene mutation carriers.

The positive predictive value was highest for mammogram and MRI together (12.4 percent), although not significantly higher than the other modalities.

In an editorial that accompanied the article, Wendie A. Berg, PhD, of University of Pittsburgh School of Medicine, wrote that “Chiarelli et al have demonstrated that a single prevalent screening MRI can be successfully introduced into an organized screening program in specific subsets of women.”

However, Berg added that “it will be important to know the performance at incidence screening MRI, the molecular subtypes and node status of cancers detected only by MRI, the interval cancer rates, and the rates of late-stage disease in the OBSP among subsets of high-risk and average-risk women to understand the efficacy of selective addition of screening MR.”