July 13, 2006

Ovary removal curbs cancer risk in high-risk women

By Martha Kerr

NEW YORK -- There is an 80 percent reduction in the risk of ovarian, fallopian tube, and peritoneal cancers among women with the BRCA1 or BRCA2 gene mutation who undergo surgery to remove both ovaries, a procedure called bilateral salpingo-oophorectomy, Canadian researchers report in the Journal of the American Medical Association.

Women with a BRCA1 or BRCA2 mutation, both of which are known to increase the risk of breast and ovarian cancers, are often advised to consider having their ovaries removed after they complete childbearing

Dr. Steven A. Narod of the Toronto-Sunnybrook Regional Cancer Center and colleagues conducted a study with 1828 women with BRCA1 or BRCA2 mutations identified from an international database from between 1992 and 2003. They followed the subjects until the diagnosis of ovarian, fallopian or peritoneal cancer, death or until the study ended.

Women were divided into three groups: 555 women (30 percent) who underwent preventive removal of both ovaries prior to study entry; 490 women (27 percent) who underwent the surgery after study entry; and 783 women (43 percent) who did not have the surgery.

After 3.5 years of follow-up, there were 50 incident ovarian, fallopian tube and peritoneal cancers, with 32 of these occurring in the women who did not undergo preventive surgery. Another 11 cases occurred at the time of prophylactic oophorectomy and 7 were diagnosed after surgery.

Narod calculates that the cancer risk reduction with preventive surgery was 80 percent. "That means that ovarian cancer can arise from other sites...20 percent occur in the peritoneum, otherwise (oophorectomy) would be 100 percent effective in preventing cancer," Narod tells Reuters Health. The peritoneum is the tissue that lines the abdominal wall and covers most of the organs in the abdomen.

At approximately age 35, BRCA1 and BRCA2 carriers should consider prophylactic removal of the ovaries. There are several reasons for choosing this age, Narod says. "First, most women have had all the children they plan to have...Only 5 percent to 10 percent indicate that they still want to have children."

"Second, age 35 offers the maximal protection. Most ovarian cancers in our study occurred around age 38," Narod explains. "By the time a woman (with the BRCA1 mutation) reaches age 50, 6 percent have ovarian cancer at the time of surgery. If the surgery is done at age 35, that number is zero."

The pattern of risk and incidence of cancer appears to be about the same with BRCA1 and BRCA2, the Toronto investigator finds.

Antioxidant vitamins and hormones such as tamoxifen may prevent cancer occurrence after prophylactic surgery, he said. There is a large study of selenium underway.

"We want to do everything we can to prevent these cancers," Narod asserts. "They are difficult to treat, which is a euphemism for saying the treatments don't work."

SOURCE: Journal of the American Medical Association, July 12, 2006.