BOSTON (Reuters) - Women who develop breast cancer because they carry one of three defective genes are no less likely to survive over the long term than other breast cancer patients, Canadian and Israeli researchers said on Wednesday.
Women with and without the best-known cancer genes had virtually the same overall survival rate after 10 years, the researchers reported in the New England Journal of Medicine.
Doctors know that the BRCA1 and BRCA2 genes increase the risk of breast cancer.
"But little is known about the influence of a BRCA1 or BRCA2 mutation on the natural history of breast cancer or the response to treatment," Gad Rennert of the National Cancer Control Center in Haifa and colleagues wrote.
They studied women treated at 22 hospitals in Israel. They found 10 percent of women of Ashkenazi Jewish heritage who had breast cancer carried mutations in one of the two genes.
Ashkenazi Jewish women are known to have a higher risk than other populations of mutations in these two genes.
The 10-year survival rate was 67 percent for women with either of the two cancer-causing mutations in the BRCA1 genes, 56 percent for the women carrying BRCA2 mutations and 67 percent for the women with none of those cancer genes.
The difference in the survival rates was not big enough to be considered significant, the researchers said.
"Among women who died from breast cancer, the median time to death was 46 months for noncarriers, 37 months for BRCA1 carriers, and 48 months for BRCA2 carriers," the researchers concluded.
On the other hand, there was a slight difference in the death rate five years after diagnosis, and the tumors among women with BRCA1 or BRCA2 tended to be more aggressive. Of the noncarriers who died from breast cancer, 68 died within five years, versus 88 percent for women with BRCA1 and 77 percent for BRCA2 mutations.
"Learning whether a patient who has just been given a diagnosis of breast cancer also bears one of the cancer-causing mutations in the BRCA1 or BRCA2 genes may add little to the clinician's ability to select a therapy or predict the course of the disease, once the grade and receptor status of the tumor and the age of the patient are taken into account," Dr. Patricia Hartge, of the U.S. National Cancer Institute, wrote in a commentary.
The Rennert group found that women with the breast cancer genes were more likely to be diagnosed with a tumor before age 50, and their tumors tended to be smaller than average and less likely to show evidence of spread to the lymph nodes.
Breast cancer kills 500,000 people globally every year, and between 5 percent and 10 percent of the 1.2 million cases diagnosed every year are inherited.