Improved screening for women at high genetic risk of breast cancer

30 June 2005

About 5% of breast cancers occur in individuals with a strong hereditary predisposition to the disease, mostly due to inherited mutations in the BRCA1 and BRCA2 breast cancer susceptibility genes. Women with either of these mutations have an approximately 80% chance of developing breast cancer by the age of 70 (compared with a general population risk of 11%); the disease typically develops at a much younger age than sporadic breast cancer. For asymptomatic women considered to be at a high risk of familial breast cancer, based on their family history and in some cases genetic testing, clinical management in the UK is based on either annual screening by mammography, or prophylactic mastectomy. As younger women (under the age of 50) have generally much denser breast tissue, mammography is less effective at early tumour detection than in older women; cancers in BRCA1 mutation carriers also tend to develop very rapidly. A high proportion of high-risk individuals therefore opt for the removal of both breasts to prevent cancer.

A new study by the Institute of Cancer Research published in The Lancet has revealed evidence compared the performance of standard mammography with that of magnetic resonance imaging as a surveillance approach for women at a high genetic risk of breast cancer [MARIBS study group (2005) Lancet doi:10.1016/S0140-6736(05)66481-1]. Contrast enhanced breast magnetic resonance imaging (CE MRI) has high sensitivity for cancer detection, even in dense breasts. The researchers reasoned that, if superior to mammography, the relatively high cost of MRI could be justified among young women with strong genetic susceptibility to breast cancer, because of their high lifetime risk of developing the disease.

The MARIBS (Magnetic Resonance Imaging Breast Screening) study set out to compare the diagnostic accuracy of annual CE MRI with X-ray mammography in young women with a high genetic risk of breast cancer. Individuals aged 35

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