They can reduce their high risk of both breast and ovarian cancer by having their ovaries removed at a young age, but this drastic measure permanently compromises their health and ends their fertility.

For women grappling with the trade-offs, a new statistical analysis by University of Pennsylvania researchers provides the best estimate to date of the value of surgery: It cuts breast cancer risk by half, and ovarian cancer risk by 80 percent, presumably by reducing exposure to the female hormone estrogen.

The numbers, while lower than some previous estimates, clearly confirm the benefits of surgery.

But the analysis, based on combining the results of 10 studies, also reveals that ovarian cancer detection and prevention strategies have not improved, 14 years after testing for BRCA gene mutations became available. Unlike breast cancer, ovarian cancer has no early-detection test and no approved drug to help prevent the disease.

"You need to have your ovaries out," said Timothy Rebbeck, the Penn epidemiologist who led the research, published in today's Journal of the National Cancer Institute. "We hoped for another option, but we haven't found one yet."

Sandy Cohen, 40, of Lafayette Hill, who had her ovaries removed last year at the Hospital of the University of Pennsylvania, said: "With all the information I gathered, I felt I didn't have a choice. This will keep me alive until they come up with something better."

The many mutations found so far in BRCA1 and BRCA2 account for less than 10 percent of the 182,000 breast cancers that occur annually in the United States. But for women who inherit one of those mutations, the specter of cancer hangs like a shroud over their families.

Instead of the normal 1.5 percent lifetime chance of ovarian cancer, their risk ranges from about 20 percent to 50 percent, studies show.

Instead of the normal 12 percent lifetime chance of breast cancer, they have at least a 50-50 chance - and some BRCA mutations virtually guarantee the disease.

These cancers tend to strike early and hard.

Cohen's grandmother, for example, died of breast cancer at age 38.

"My mother grew up without a mother," Cohen said, "so every year after she turned 38, she was sure she was going to get breast cancer. The fear was ingrained in me, too."

Her mother made it to 54 before dying of the disease in 1994, the year that BRCA1 was discovered.

"I was so scared," Cohen recalled. "I went to meetings about genetic testing, but I wasn't ready. I wasn't married and I didn't have children."

Expert guidelines have long recommended that women with such strong hereditary predispositions have an "oophorectomy" - removal of ovaries and fallopian tubes - by age 35, or as soon as they finish having children.

The surgery plunges the woman into premature menopause with severe hot flashes, and raises "important and difficult questions," Rebbeck wrote. The unnatural loss of ovarian estrogen raises the woman's risks of developing heart disease, osteoporosis and dementia, yet long-term hormone replacement therapy has been shown to increase the risks of breast cancer and dangerous blood clots.

Postponing surgery may be safe in some cases because high-risk women develop ovarian cancer on average at age 50, Rebbeck said. On the other hand, BRCA1 mutation carriers, who are at highest risk of ovarian cancer, tend to develop it younger.

Studies also suggest that up to 10 percent of women already have microscopic amounts of the cancer when they undergo preventive oophorectomy.

This undetected cancer can stay behind to seed malignancy even after surgery, which is why removing the ovaries does not guarantee full protection.