November 5, 2019 -- The performance of the cancer antigen 125 (CA-125) blood test for detecting ovarian cancer surpassed expectations in a study of more than 50,000 symptomatic women seen in primary care, researchers reported on November 5 at the U.K. National Cancer Research Institute (NCRI) meeting in Glasgow.
In the study of 50,780 women with symptoms of ovarian cancer such as bloating and abdominal pain, 6.8% had an abnormally high level of CA-125 -- defined as at least 35 U/mL. Of those with high levels, it turned out that 10% had ovarian cancer, the researchers shared in a poster presentation.
"This figure is much higher than previously thought and 10 times higher than the estimate given in the U.K.'s 2011 NICE (National Institute for Health and Care Excellence) guidelines on ovarian cancer diagnosis," the NCRI said in a statement.
The association was stronger for women 50 years or older: Of the 31,086 women, 15% with a high level of CA-125 developed ovarian cancer. In comparison, 3% of those younger than 50 who had a high CA-125 level developed ovarian cancer. The results suggest that women with abnormally high levels of CA-125 should be quickly followed up with more testing for ovarian cancer and possibilities for earlier diagnosis to improve prognosis.
In another poster presentation of the same study cohort, the researchers reported that 17% of those 50 or older who had a high level of CA-125 developed a different kind of cancer, including tumors in the pancreas, lung, liver, and gastrointestinal tract.
"In women 50 years and older, the incidence of [nonovarian] cancers was more than [six] times higher in those with elevated CA-125 levels than normal levels," Dr. Garth Funston, a clinical research fellow at the University of Cambridge, and colleagues noted.
However, in looking at different types of cancers individually, the numbers were small. Therefore, while it's good for doctors to be on the lookout for other cancers, the CA-125 test is insufficient on its own, the researchers concluded.