The risk for a new cancer in the unaffected breast substantially increases in women diagnosed with unilateral, hereditary ( non-BRCA ) breast cancer.

A study reveals women under 50 diagnosed with hereditary ( non-BRCA ) breast cancer are at significantly greater risk for developing cancer in the other breast, also known as contralateral breast cancer ( CBC ).
Adjuvant hormonal therapy, however, reduces contralateral breast cancer risk.

Women with hereditary ( non-BRCA ) breast cancer are estimated to be at up to six times greater risk of developing a second primary malignancy in the other breast 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 contralateral breast cancer .
However, the contribution of non-BRCA hereditary cancers to the risk of contralateral breast cancers is poorly understood.

Led by Katarina Shahedi, of the Umeå University and colleagues at the Karolinska Institute in Stockholm, Sweden, researchers 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 contralateral breast cancer risk for these women.

They found that the long term contralateral breast cancer 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 contralateral breast cancer was significantly elevated for women under 50 years old compared to women over 50 years old ( 40 percent and 10 percent, respectively ).

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

In the first published study to characterize contralateral breast cancer risk in non-BRCA hereditary breast cancers, the authors demonstrate " that women with hereditary/familial non-BRCA1/BRCA2 breast cancer have a very high risk of developing contralateral breast cancer."

The impact of these results is most apparent for premenopausal women, in who 1 in 5 will develop contralateral breast cancer after only 10 years.

Source: Cancer, 2006


XagenaMedicine2006