A study of women with hereditary breast cancer that is not due to mutations in BRCA1 or BRCA2 reports that these women have a high risk of subsequently developing breast cancer in the opposite breast (contralateral breast cancer). These results were published in the journal Cancer.
Between 5% and 10% of all breast cancers are thought to be linked with inherited gene mutations. Inherited mutations in two genes-BRCA1 and BRCA2-greatly increase the lifetime risk of developing breast and ovarian cancer, but may explain only a minority of all hereditary breast cancer.
Women with BRCA1 or BRCA2 mutations are known to have a high risk of developing contralateral breast cancer after an initial breast cancer diagnosis, but the risk among women with hereditary breast cancer that is not due to BRCA1 or BRCA2 mutations has received less attention.
To assess the frequency of contralateral breast cancer in women with hereditary non-BRCA-related breast cancer, researchers in Sweden conducted a study among 204 breast cancer patients from 120 families. The families had been referred to a genetics clinic for suspected hereditary breast cancer. The study excluded women who were initially diagnosed with bilateral breast cancer (cancer in both breasts), as well as women who tested positive for BRCA1 or BRCA2 gene mutations.
- After 20 years, the probability of developing contralateral breast cancer was 27% among women with hereditary breast cancer, compared to 5% among women with breast cancer in the general population.
- The risk of contralateral breast cancer was highest among women with hereditary breast cancer that was diagnosed before the age of 50. More than 40% of these women were expected to develop contralateral breast cancer during the 20 years after their initial breast cancer diagnosis.
- Adjuvant hormone therapy reduced the risk of contralateral breast cancer.
The researchers conclude that women with hereditary non-BRCA-related breast cancer have a high risk of subsequently developing cancer in the opposite breast. Risk was particularly high for women who were initially diagnosed with breast cancer at a young age. The researchers note that “When genetic counseling is provided for this group of women, it is important to consider and provide information regarding the risk of [contralateral breast cancer].”
Reference: Shahedi K, Emanuelsson M, Wiklund F et al. High Risk of Contralateral Breast Carcinoma in Women with Hereditary/Familial Non-BRCA1/BRCA2 Breast Carcinoma. Cancer. 2006;106:1237-42.