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Ovarian cancer blood test more effective than previously thought

2 November 2020
Appeared in BioNews 1070

A blood test already used to diagnose ovarian cancer is far more predictive than originally thought and may also diagnose other types of cancer.

The Cancer Antigen 125 (CA125) blood test is used worldwide as a first step in the diagnosis of ovarian cancer in women who already have symptoms. The CA125 protein is often found on the surface of ovarian cancer cells but raised levels can also occur due to endometriosis, fibroids or pregnancy. Hence, further definitive tests are required for women who have a high level of the CA125 biomarker, such as an ultrasound.

'The CA125 blood test has been around and available to GPs for a while. But it's never actually been evaluated in primary care,' explains Dr Garth Funston, from the University of Cambridge, who led the study. 'Tests perform differently depending on how you use them and who you use them in. So to really understand how this test performs, we needed to study it in the population in which it was used.'

A team of researchers, based at the Universities of Cambridge, Manchester and Exeter and funded by Cancer Research UK and the National Institute for Health Research, further investigated the CA125 blood test for ovarian cancer and published their findings in PLOS Medicine.

The scientists, working as part of the CanTest collaborative, investigated 50,000 women who had seen their GP and taken the CA125 test between 2011 and 2014. Ten percent, over 350 women, with higher CA125 levels were subsequently diagnosed with ovarian cancer, which makes an abnormal test result 12 times more predictive than previously believed.

Furthermore, a raised CA125 level was also indicative of other types of cancer, such as bowel, lung and pancreatic cancer. The study identified that more than 380 women with raised CA125 levels went on to be diagnosed with cancer other than ovarian.

The study also highlighted that age was a definitive factor: 33 percent of women diagnosed with any cancer were aged over 50, in comparison to only six percent aged under 50.

The scientists went on to develop models, based on both age and the level of CA125 in the blood, which give an individualised risk or probability of a woman having cancer. GPs are able to use these models to determine which patient requires further testing.

Dr Jodie Moffat, head of early diagnosis at Cancer Research UK concluded: 'This research demonstrates a readily available and tangible test that can be used more often by GPs to give people more time with their loved ones. Significant investment in diagnostic equipment and technology, along with NHS staff is urgently needed to diagnose more cancers at an earlier stage and save lives. Through the right investments and policies, the UK has the potential to become a world leader in the early detection and diagnosis of cancer.'

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