Screening for Ovarian Cancer Saves Few Lives
New Model Suggests Screening Less Useful Than Previously Thought
Dec. 13, 2010 -- Like breast cancer, the survival rate for ovarian cancer can be high when the disease is detected early, before it spreads.
But unlike breast cancer, early detection of ovarian cancer is rare.
The long search for effective screening strategies to identify ovarian cancer in average-risk women before symptoms occur has proved disappointing.
Now a new understanding of the complexity of the disease further dims hopes for effective early screening in the near future, Duke University researchers say.
“Screening alone with the tests we have now is not going to get us where we want to be,” researcher Laura Havrilesky, MD, of the Duke Cancer Institute, tells WebMD. “We have to look at other ways to reduce deaths from ovarian cancer.”
Ovarian Cancer: Two Diseases
Nearly 22,000 women in the U.S. will be diagnosed with ovarian cancer this year and 14,000 will die of the disease, according to the American Cancer Society (ACS).
Five-year survival when the cancer is found before it has spread beyond the ovaries is more than 90%, but less than 20% of ovarian cancers are detected in the early stage before it has spread outside the ovary.
Ovarian cancer has long been thought of as a single disease, but researchers have recently learned that it has different subtypes, including a relatively slow-growing form and a more aggressive form that takes about half the time to progress to advanced stages.
Using this knowledge, Havrilesky and colleagues developed a computer-based model to predict the impact of currently used screening methods on ovarian cancer deaths.
These methods include testing for elevated levels of the protein CA-125 in the blood and pelvic imaging using ultrasound.
CA-125 levels rise in women with ovarian cancer, but they can also be elevated in women who are pregnant, who have other cancers, or non-cancerous conditions such as uterine fibroids.
The Duke researchers modified an established model of the progression of ovarian cancer to reflect the fast-growing and slower-growing forms of the disease.
They tested their model using early data from a large screening trial now under way in the U.K.
Instead of the 15% to 20% reduction in ovarian cancer deaths attributed to early screening based on the ‘one cancer’ model, the new model found that the death rate could be expected to fall by about 11% if annual screening using current strategies were routinely recommended for all postmenopausal women.
Havrilesky says this is because screening is more likely to pick up slow-growing cancers that are not as lethal.
The study appears online today in the online edition of the journal Cancer.
UK Trial Should Provide Some Answers
In the U.S., screening is generally reserved for women with a close family history of ovarian cancer or a genetic mutation that greatly increases their cancer risk.