Ovary Removal Lowers Odds of Cancer in High-Risk Women
Tuesday, January 13, 2009; 12:00 AM
TUESDAY, Jan. 13 (HealthDay News) -- Removing the ovaries of women with a high risk of breast and ovarian cancer due to mutations in BRCA1 or BRCA2 genes does substantially reduce their risk of getting both cancers, a new study confirms.
Researchers from the University of Pennsylvania School of Medicine and Memorial Sloan-Kettering Cancer Center did what's known as a meta-analysis, pooling the results of several studies and re-analyzing them. Led by Dr. Timothy Rebbeck, a professor of epidemiology at the university, the research team looked at 10 published studies. The report appears in the Jan. 13 issue of the Journal of the National Cancer Institute.
The risk reduction, he said, is substantial but perhaps not as high as earlier studies have suggested.
But not everyone agrees with that assessment. An expert who reviewed the study said the actual risk reduction may be higher than Rebbeck's team found because surgical techniques and preventive approaches have improved since some of the studies they analyzed were done.
Rebbeck said that "the earlier studies in this area were suggesting something like a 95 percent risk reduction, a near complete reduction [in ovarian cancer risk] that was very encouraging." But his team found somewhat less of a risk reduction with the procedure that involves removing the ovaries and fallopian tubes, called a prophylactic salpingo-oophorectomy. They found a 79 percent reduced risk of ovarian cancer and a 51 percent reduced risk of breast cancer.
"The breast cancer number has been pretty consistent throughout history," Rebbeck said.
Women who have inherited mutations in the BRCA1 or BRCA2 genes have elevated risks of both breast and ovarian cancer. The lifetime risk of breast cancer ranges from 56 percent to 84 percent, according to the researchers, whereas the risk for ovarian cancer ranges from 36 percent to 46 percent for BRCA1 mutation carriers and 10 percent to 27 percent for BRCA2 mutation carriers.
Women with these gene mutations usually are counseled to help them choose strategies to reduce the risk, which might include removing the ovaries or breasts, as well as screening and other prevention techniques.
But even removal of the ovaries cannot guarantee that a woman will never get ovarian cancer, Rebbeck said. Sometimes, for instance, ovarian cells get left behind in the surgery, he explained.
Dr. Jeffrey N. Weitzel, chief of the division of clinical cancer genetics at the City of Hope Comprehensive Cancer Center in Duarte, Calif., said pooling the results of 10 studies provided "enough [statistical] power to have a strong observation of a beneficial effect for BRCA1 and BRCA2 carriers."
By combining studies, "we get greater confidence there is a high likelihood this is a real effect," he said.
But in reality, a woman undergoing preventive removal of the ovaries today would probably have "closer to a 90 percent" reduction in ovarian cancer risk, Weitzel estimated. That's because, he said, the surgery that's done now is more thorough than it was in years past.
For women who are BRCA1 or BRCA2 carriers, preventive ovary removal is often recommended at age 35 or after completion of childbearing, Rebbeck said. Another way to reduce risk would be for a woman to go on oral contraceptives in her 20s, before childbearing, he said.
To learn more about the risk factors for ovarian cancer, visit the American Cancer Society.
SOURCES: Timothy Rebbeck, Ph.D., professor, epidemiology, University of Pennsylvania School of Medicine, Philadelphia; Jeffrey N. Weitzel, M.D., chief, division of clinical cancer genetics, and professor, oncology and population science, City of Hope Comprehensive Cancer Center, Duarte, Calif.; Jan. 13, 2009, Journal of the National Cancer Institute, online