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TORONTO (CP) - Even after having their ovaries and fallopian tubes removed on a preventive basis, women who carry one of two gene mutations known to be linked to high rates of breast and ovarian cancer are still at risk of developing a form of ovarian cancer, cancer in the peritoneum, a large international study released Tuesday confirms.
About four per cent of women who had the preventive procedure, called a salpingo-oophorectomy, went on to develop peritoneal cancer within 10 years of the operation, the researchers, from the Hereditary Ovarian Cancer Clinical Study Group, reported in the Journal of the American Medical Association.
Senior author Dr. Steven Narod, a leading researcher in the field of inherited breast and ovarian cancers, said that means that even after having their ovaries and fallopian tubes removed women with the mutations - known as BRCA1 or BRCA2 - still face a risk of developing peritoneal cancer that is significantly higher than that faced by women who didn't inherit either of the genes.
"It's still nine times higher than the average woman," said Narod, director of the familial cancer research unit at Toronto's Women's College Hospital.
"Is it bad news? Well, one would like to think you have your organs removed and the disease is not going to come."
The nine-fold increased risk Narod referred to relates to the difference between the chances of a woman with one of these mutations developing any type of ovarian cancer as compared to the chances of an average woman developing any type of ovarian cancer.
Peritoneal cancer is one of three closely intertwined cancers that are generally lumped together under the umbrella of ovarian cancer.
Ovarian cancer is one of the so-called silent cancers, which in the early stages has vague symptoms that are often missed. By the time diagnosis is made, the disease has generally progressed to the point where it is found in the ovaries, fallopian tubes and in the peritoneum, the membrane that encloses the abdominal cavity.
Each site can be the source of the primary cancer. But because all three will generally become involved if the disease is not discovered and checked early by surgery, it's often almost impossible to tell where the cancer began.
The average Canadian woman has about a 1.4 per cent lifetime risk of developing ovarian cancer; the risks for women with the BRCA1 and BRCA2 mutations are 60 per cent and 25 per cent respectively.
A protective salpingo-oophorectomy cut that risk by 80 per cent, Narod and his colleagues reported based on a study of 1,828 Canadian, American, European and Israeli women with one of the two genes.
Fifty-seven per cent of the women - 1,045 - had their ovaries and fallopian tubes removed of their own volition, either before the beginning of the study or at a point during the follow up. The remainder did not undergo the operation during the study time frame.
Women with the BRCA1 and BRCA2 mutations are at a vastly elevated risk of developing breast cancer and ovarian cancers as well. Even women who have their breasts removed to eliminate their risk of breast cancer can go on to develop ovarian cancers.
And as this study quantifies, even removing the ovaries and the fallopian tubes isn't perfect protection.
"It's not what we call preventive. It's risk reducing, but it doesn't prevent cancer completely," said Tim Rebbeck, a researcher from the University of Pennsylvania who has done studies looking at the protective power of oophorectomies.
"You would think that removing your ovaries would prevent you from being at risk of ovarian cancer. But it doesn't. There is residual risk even after you've had your ovaries removed."
The study was supported by grants from the Canadian Breast Cancer Research Alliance and from U.S. National Institutes of Health.
© The Canadian Press, 2006
