Non-BRCA1/2 Hereditary Breast Cancer Linked to New Cancers

The risk for a new cancer in the unaffected breast substantially increases in women diagnosed with unilateral, hereditary (non-BRCA1/2) breast cancer, according to a new study by researchers working at Karolinska Institutet in Stockholm, Sweden. The study is the first in its kind and is published in the March 15, 2006 issue of CANCER.

Women with hereditary (non-BRCA1/2) breast cancer are estimated to be at up to six times greater risk of developing a second primary malignancy in the other breast, also known as contralateral breast cancer (CBC), than the general population is of developing primary breast cancer. Young age at first diagnosis, family history of breast cancer, and confirmed BRCA1 or BRCA2 gene mutations are the primary risk factors for CBC. However, the contribution of non-BRCA1/2 hereditary cancers to the risk of CBC is poorly understood.

A group of researchers at Karolinska Institutet and Umeå Universitet in Sweden reviewed data from 120 families and 204 women with unilateral breast cancer and a family history of breast cancer but no BRCA mutations to better characterize the CBC risk for these women.

They found that the long term CBC risk was significantly higher in women with hereditary breast cancer compared to the risk of developing a primary breast cancer in the general population. The overall probability for these women was 5.5 percent at 5 years and up to 27.3 percent at 20 years compared to only 1.9 percent at 5 years and 4.9 percent at 20 years for the general population. Further analysis by age group showed clearly that the 15 year probability of developing a CBC was significantly elevated for women with a diagnose before age 50 compared to women at an older age (40 percent and 10 percent, respectively).

Women who received adjuvant hormonal therapy had significantly lowered risk for a CBC compared to those who did not take it. Adjuvant chemotherapy had no apparent effect on risk.