Report from ISMRM: Dynamic CE-MRI excels as screening test for women carrying genetic risks for breast cancer

May 10, 2006

New evidence shows that dynamic contrast-enhanced MRI and conventional x-ray mammography play complementary roles in screening women who are genetically susceptible to breast cancer.

New evidence shows that dynamic contrast-enhanced MRI and conventional x-ray mammography play complementary roles in screening women who are genetically susceptible to breast cancer.

Results from an initial screening and at least one year of follow-up tests on 649 genetically at-risk women indicate that MRI is more sensitive than x-ray mammography, particularly with BRCA1 mutation carriers. MRI is less sensitive, however, for women with a BRCA2 mutation or family history of breast or ovarian cancer. Performing mammography with MRI improves cancer detection.

Dr. Martin Leach, a professor of physics as applied to medicine at Royal Marsden Hospital in Sutton, U.K., announced the most recent findings from the multicenter Magnetic Resonance Imaging for Breast Screening (MARIBS) Trial at the International Society for Magnetic Resonance in Medicine meeting in Seattle on Tuesday.

The genetic propensity of some women to develop breast cancer may outweigh the otherwise high cost of MRI breast screening. Two percent of breast cancers are related to BRCA1 and BRCA2 mutations, and between 45% and 55% of the affected women develop cancer by age 70. Their annual risk of breast cancer development between ages 35 and 50 is at least 20 times higher than that of the general female population in that age group, Leach said.

The MARIBS protocol involved annual MRI and mammography and blinded double readings, with at least one additional annual screening when positive findings were not found. The women's genetic status was established before testing and confirmed following positive findings. Testing was performed at 22 sites in the U.K.

Thirteen breast cancers were diagnosed among women with a BRCA1 mutation, 12 were found among women with the BRCA2 gene, and 10 were identified in subjects who tested negative for both mutations but had a family history of breast and ovarian cancer.

For BRCA1 subjects, dynamic CE-MRI was 92% sensitive to the presence of breast cancer compared with 23% for x-ray mammography. The combined tests were 92% sensitive, indicating that x-ray mammography added nothing to the sensitivity of the screening exam.

MRI screening was less potent for BRCA2 carriers at 58% sensitivity, while x-ray mammography had a sensitivity of 50%. Dynamic CE-MRI and conventional mammography combined, however, were 92% sensitive to breast cancer.

For women with a family history of breast cancer, the sensitivity rates for dynamic CE-MRI and x-ray mammography were 80% and 50%, respectively. Performed together, they were 100% sensitive to disease.

"These results indicate that we are detecting different types of breast cancers with the two techniques," Leach said.

BRCA1 and BRCA2 carriers mainly developed high-grade cancers, while the family history subjects had a more varied distribution of cancer grades. More ductal carcinoma in situ was seen among BRCA2 subjects than with the BRCA1 group. The BRCA1 group tended to be lymph node-negative and receptor-negative for estrogen and progesterone. Cancers arising among BRCA2 carriers, however, tended toward more lymph node involvement and were more often positive for estrogen and progesterone receptors. In the family history group, proportionally fewer positive nodes and more uniform distribution of receptor status were observed.

The MARIBS study concurs with three large clinical trials that have recently established that MRI is 70% to 77% sensitive to breast cancer for at-risk women, much higher than the 40% sensitivity range of conventional mammography.

"If we can build on this information in consultation with other study investigators, we will get clearer guidelines as to the relative importance of difference screening techniques in these different groups," Leach said.

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