The average woman has a 12 per cent risk of developing breast cancer sometime during her life. In women like actress Angelina Jolie who carry the BRCA1 mutation, the lifetime risk for breast cancer is about five times higher.
The BRCA1 and 2 mutations account for about five per cent of all breast cancers.
Researchers from Women's College Research Institute in Toronto compared 345 women in Canada and the U.S. with Stage I or II breast cancer and a BRCA 1 or BRCA2 mutation who had an oophorectomy, or ovary removal surgery, to 331 others who kept both ovaries.
The 20-year survival for the entire group was 77 per cent, nursing professor Kelly Metcalfe and her co-authors said in Wednesday's online issue of JAMA Oncology. The researchers found preventive oophorectomy is associated with better prognosis in terms of breast cancer survival.
Within 1st year
"Prophylatic oophrectomy has definitely been on the table as an option; however, it hasn't been pushed," Metcalfe said. "Typically, women would be advised to … think about your breast cancer and treat that, and if you do OK, we'll think about preventing the ovarian cancer. I think this research shows that we can't put it off.
"If we could maximize the benefit associated with oophrectomy, we would want to do the surgery within the first year after breast cancer diagnosis."
Oophrectomy is now known to help treat a first breast cancer, prevent a second primary breast cancer and prevent ovarian cancer, all of which improve survival.
Metcalfe hopes the findings lead to a shift in thinking to expand how many women opt for the surgery.
"Women with a BRCA mutation are now offered a bilateral mastectomy as part of their initial surgery," she said.
"Hopefully, we can get this implemented into clinical practice, too, that it is seen as part of your breast cancer treatment and not prevention of ovarian cancer in the future. That may help women to have this done in a more timely and appropriate time period to increase their chance of survival."
In the study, oophrectomy was performed an average of six years after breast cancer diagnosis.
There was 73 per cent reduction in mortality if women had surgery done within the first two years compared with a 62 per cent reduction if it was done at any time.
The benefit extended to women diagnosed after age 50. The majority of the surgeries were done to prevent ovarian cancer and not to treat breast cancer, the researchers said.
The survival benefit was only seen for those with BRCA1. It could be too few women with BRCA2 were included, biological differences such as how BRCA2 resembles sporadic breast cancer, or a combination, Metcalfe speculated.
Women in the study were diagnosed between 1975 and 2008 and followed for an average of 12.5 years. Over that time, treatments have changed, which the researchers took into consideration. The findings may not apply to women with advanced-stage breast cancer and need to be confirmed.
Practice won't change
A journal editorial published with the study called it a validation of the role of oophorectomy.
"The data reported here are compelling and suggest that the potential of oophorectomy should become part of the treatment discussion at the time of diagnosis for BRCA mutation carriers with early-stage breast cancers," said Dr. Mary Disis, the journal's editor-in-chief.
Dr. Eitan Amir, an oncologist at Princess Margaret Cancer Centre in Toronto, said oophorectomy is already advised, so the findings won't change practice at his hospital. He said the benefits for women who are estrogen negative could be new, but it's also possible there were testing flaws.
The study was funded by the Canadian Breast Cancer Foundation (Ontario chapter). Disis received research grant funding from Seattle Genetics and pharmaceutical companies EMD Serono and VentriRx as well as stock options in the two companies.