Testing for levels of the serum biomarker cancer antigen 125 (CA125) in the blood may be a useful tool for the detection of ovarian cancer, and could help detect other types of cancer among patients in primary care, according to research presented by Funston et al at the 2019 National Cancer Research Institute (NCRI) Cancer Conference.

Although the CA125 test is already in use in countries around the world, this is the first large study to look at how well it performs in general practice for testing women who have possible symptoms of ovarian cancer. Researchers said their results could help to guide women and general practitioners on whether more invasive tests are needed to check for ovarian and other cancers. They also say that clinical guidelines could now be improved to ensure urgent referrals are made for women most at risk.

The research was led by Garth Funston, MB, BChir, a clinical research fellow at the University of Cambridge. He explained, “Less than half of women with ovarian cancer survive for 5 years following diagnosis. The majority of women are not diagnosed until the disease is advanced, which makes it more difficult to cure. It’s important that general practitioners have effective tools to detect ovarian cancer early and ensure patients are referred appropriately. While CA125 is widely used in general practice in the UK and internationally, prior to this study, it was unclear how effective a test it really was in general practice.”

Methods

The research included data on 50,780 women who visited general practitioners in England with possible signs of ovarian cancer (such as persistent bloating or abdominal pain) and were tested for levels of CA125 in their blood between May 2011 and December 2014. Ovarian cancers diagnosed in the 12 months following testing were identified from the cancer registry. Researchers calculated the probability of having ovarian cancer given a CA125 at or above a set cut-off and the probability of having ovarian cancer given a specific CA125 level for women younger than age 50 and older than age 50.

Results

50,780 women underwent CA125 testing; 456 (0.9%) were diagnosed with ovarian cancer. Researchers found that 10% of women who had an abnormally high level of CA125 in their blood were found to have ovarian cancer.

In women who had abnormal test results and were aged 50 years or older, 15% were found to have ovarian cancer, while in women under 50 with high CA125 levels, 3% were diagnosed with ovarian cancer.

Results also showed that around 17% of women 50 years or older with an abnormal result were diagnosed with another form of cancer, such as pancreatic, lung, or uterine cancer.

The amount of CA125 in the blood is measured in units per milliliter (U/ml). Dr. Funston and his colleagues found, for example, that women with a CA125 level of 51 U/ml had a 3% probability of ovarian cancer—the level of risk at which the National Institute for Health and Care Excellence recommends urgent cancer referral.

Dr. Funston concluded, “Our work shows that CA125 is a very useful test for detecting ovarian cancer in general practice. This could help guide decisions made by general practitioners and their patients about the need for further investigation or referral. Our findings also highlight that women with symptoms who are aged 50 years or more and have abnormally high CA125 levels frequently have other types of cancer. It is really important that general practitioners are aware of this to ensure these cancers are not missed.”

Disclosure: For full disclosures of the study authors, visit abstracts.ncri.org.uk.