It is widely known that having a BRCA1 gene mutation increases risk of female breast and ovarian cancers. And now, findings from a large international study suggest that women with these mutations should have preventive surgery to remove the ovaries by the age of 35, rather than waiting until a later age when the risk of ovarian cancer greatly increases.

According to the National Cancer Institute, about 1.4% of women in the general population will develop ovarian cancer at some point in their lives. However, for women who inherit a BRCA1 mutation, 39% will develop ovarian cancer.

Because of these risks, researchers - led by Amy Finch and Dr. Steven Narod of Women's College Hospital in Canada - wanted to estimate the reduction in risk of death due to ovarian, fallopian tube or peritoneal cancer in women with a BRCA1 or BRCA2 mutation after oophorectomy (removal of the ovaries).

They published the results of their study in the Journal of Clinical Oncology.

The team notes that as many as 70% of women in the US who are aware they have BRCA mutations opt for removal of the ovaries, and many doctors suggest these women have the surgery by age 35 or when they no longer wish to bear children.

But until now, the best age for having the surgery - or its effects on overall mortality risk - had not been studied.

Finch, a researcher at Women's College Research Institute, says:

"Scientific evidence clearly shows removal of a woman's ovaries and fallopian tubes is very effective in preventing both breast and ovarian cancer in women with a BRCA mutation. But the real question has been at what age these women should have the surgery to best diminish their chance of developing cancer."

To find out, researchers from Canada, the US, Poland, Norway, Austria, France and Italy pinpointed women in an international registry who had BRCA mutations. In total, 5,787 completed questionnaires about reproductive and surgical history - including preventive ovary removal and mastectomy - and hormone use.

Preventive oophorectomy reduces death risk by 77%

Beginning in 1995, the study followed the women through 2011, and researchers looked at the relationship between preventive ovary surgery and the overall death rate by age 70.

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Early removal of the ovaries in women with BRCA1 mutations resulted in a 77% reduction in overall risk of death, researchers found.

Of the 5,787 women in the study, 2,274 did not have their ovaries removed, while 2,123 had already done so by the start of the study and 1,390 underwent the surgery during the follow-up period, which lasted an average of 5.6 years.

The researchers found that 186 women developed either ovarian, fallopian tube or peritoneal cancer.

However, the team discovered that oophorectomy reduced ovarian cancer risk by 80%. Meanwhile, women with a BRCA1 mutation who delayed surgery until the age of 40 increased their risks of ovarian cancer to 4%, and those who waited until the age of 50 increased risks to 14.2%.

In total, 511 women died during the study - 333 from breast cancer, 68 from ovarian, fallopian tube or peritoneal cancers. The rest died of other causes.

Having preventive oophorectomy reduced the risk of death - by any cause - by 77%, the researchers note.

Dr. Narod adds that this decreased risk is better than the benefit of chemotherapy and was just as strong for carriers of BRCA1 and BRCA2 mutations.

He says:

"To me, waiting to have oophorectomy until after 35 is too much of a chance to take. These data are so striking that we believe prophylactic oophorectomy by age 35 should become a universal standard for women with BRCA1 mutations."

He adds that women with BRCA2 mutations can safely wait until their 40s for the surgery, as "their ovarian cancer risk is not as strong."

Further research needed for long-term effects

Though removal of the ovaries is a safe procedure, the researchers note that it can carry complications, such as early menopause.

"After an oophorectomy, the long-term effects on a woman's cardiovascular health and her bone health are less well known, and further research is needed," Finch adds.

However, the National Cancer Institute state that an added benefit of oophorectomy is that it also reduces the risk of breast cancer in premenopausal women by removing a source of hormones that fuel the growth of certain types of breast cancer.

The organization also says that harmful BRCA1 and BRCA2 mutations are "relatively rare in the general population," so most experts advise that genetic mutation testing should only be carried out in women who don't have cancer when the family history suggests these mutations may be present.

Medical News Today recently reported on a study that suggested daily aspirin use reduces ovarian cancer risk by 20%.