THURSDAY, May 10 (HealthScout) -- Women whose genes put them at increased risk of ovarian cancer can reduce their odds of developing the disease by having their fallopian tubes tied, a new study says.
Many women who've finished childbearing undergo the procedure, also known as tubal ligation, because the operation has been shown to lower the risk of ovarian cancer.
But the latest work, led by Canadian researchers, is the first to show that the protection extends to women with a strong genetic predisposition to both ovarian and breast cancer. The May 12 issue of The Lancet reports the findings.
Women with mutations of BRCA1 genes have a lifetime risk of ovarian cancer of 40 roughly percent, about 30 times more than average. For those with errors in related genes, called BRCA2, the increase is 25 percent or more, depending on the location of the flaws. Taken together, mutations in the two genes account for 10 percent of cases of invasive ovarian cancer in North America.
Earlier studies show that women in general can cut their odds of getting ovarian cancer by 50 percent to 60 percent by having their tubes tied, a birth control procedure that prevents sperm from reaching eggs. The new study of British, Canadian and American women suggests the operation is equally protective for women at far higher risk of the disease.
A research team led by Dr. Steven Narod of the University of Toronto found that women with mutant BRCA1 genes who had had tubal ligation were 60 percent less likely than those with intact fallopian tubes to develop ovarian cancer. Thirty of 173 women, or 18 percent, with ovarian cancer had had the tube surgery compared with 60 of 173, or 35 percent, without the disease.
Those who also had been taking birth control pills had a 72 percent reduced risk of ovarian cancer, say the researchers.
The study found no reductions in risk of ovarian cancer among women with abnormal BRCA2 genes, although the number of such women in the study was quite small.
While oral contraceptives and multiple pregnancies reduce the risk of ovarian cancer, tubal ligation has the advantage of being the quickest to prescribe, Narod says. The whole process, from getting a gene test for BRCA mutations to having the operation, can take a month or less, he says. "That's the first kind of intervention we have that has that kind of timeliness to it," Narod says.
He says the only reason the essentially benign procedure isn't more common as a preventive measure against ovarian cancer is that the chances of getting the disease are so low. Some women at particularly high risk of ovarian tumors elect to have their ovaries removed entirely, an operation that has much more serious side effects, including triggering menopause and all its attendant tribulations.
The question now is not whether but how tubal ligation prevents ovarian cancer, experts say. Scientists theorize that the procedure protects the ovaries by reducing the flow of certain hormones to the organs, and some have suggested that severing the fallopian tubes blocks the ovaries from exposure to harmful infectious agents.
But Narod says he's not satisfied with either of those explanations or any other yet offered.
Dr. Henry Lynch, a Creighton University preventive medicine expert and a co-author of the study, says, "This is empirical and observational, and it works, but we really don't have a good answer" as to why.
What To Do
To learn more about the genetics of ovarian and breast cancers, check this site from the National Cancer Institute, or visit Cancer Care.
For more on tubal ligation, try the University of Michigan
Other HealthScout articles discuss ovarian cancer.
