Elevated levels of three proteins show ovarian cancer is starting to grow years before women are diagnosed, but they do not increase soon enough to be an early indicator of the disease, U.S. researchers said on Wednesday.
The researchers analyzed blood samples from a large clinical trial and identified 34 women with ovarian cancer along with a control group of 70 women who did not have cancer. Their blood samples were used to evaluate six proteins identified as potential indicators of ovarian cancers.
Levels of three of the proteins began to increase slightly in ovarian cancer patients three years before diagnosis but did not reach a level that could be detected in a screening program, the researchers wrote in the Journal of the National Cancer Institute.
"Even though an elevation appears to start in women with cancer maybe three years before her symptoms lead her to the doctor the levels aren't really what we'd probably define as abnormal until within the last year before diagnosis," wrote lead author Garnet Anderson of the Fred Hutchinson Cancer Research Center in Seattle.
There is no simple and reliable screening program to test for ovarian cancer in women who do not have symptoms.
Ovarian cancer, which mainly strikes older women, causes more deaths than any other cancer of the female reproductive system. Women diagnosed in the earliest stages have a five-year survival rate of nearly 93 percent, according to the American Cancer Society.
SEEKING EARLY DETECTION
Researchers seeking to a screening program to detect ovarian cancer are looking for something similar to the PSA for prostate cancer, Anderson said.
PSA, or Prostate-specific antigen, is a protein monitored for early detection of prostate cancer in men.
"We'd like that for ovarian cancer because it's clear that women who are detected at the stage where the disease is still confined to the ovaries do very well. Their prognosis is excellent," Anderson said.
"CA125, which is one of the markers we looked at, is the best biomarker that's been identified to date and our study confirms that and this prediagnostic period as well. But it's not sufficiently accurate."
In an accompanying editorial, Patricia Hartge of the National Cancer Institute said the authors had taken research at step closer to a successful screening design.
"The careful evaluation technique applied in the current study fits into a staged approach necessary for testing performance of early markers of disease," Hartge wrote.
The U.S. Centers for Disease Control and Prevention estimates that more than $2.2 billion is spent on the treatment of ovarian cancer per year in the United States.