SUNDAY, Sept. 19 (HealthDay News) -- Newly identified gene mutations may affect breast cancer risk in some women, an international team of researchers has found.

It is already known that BRCA1 gene mutations substantially increase the risk of breast and ovarian cancer. This new study looked at whether other gene mutations might modify or alter that breast cancer risk.

The Mayo Clinic-led team first studied genetic mutations in 1,193 women with BRCA1 mutations who had invasive breast cancer and 1,190 women with BRCA1 mutations who didn't have breast cancer. They then used those findings to study a larger sample of women in each group.

The investigators eventually identified five gene mutations in the region of chromosome 19p13 that modify breast cancer risk in women with BRCA1 gene mutations. But these mutations do not affect ovarian cancer risk in these women, the researchers noted.

The findings, published in the current issue of the journal Nature Genetics, may help improve understanding of the causes of breast cancer and "should be useful in helping determine individual risk for breast cancer in BRCA1 carriers," senior author Fergus Couch said in a news release from the Mayo Clinic.

More information

The American Cancer Society has more about breast cancer.