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Can a CA125 blood test be used as a screening tool for ovarian cancer?

03 October 2022

CA125 blood test

We’re often asked whether the CA125 blood test can be used as a way of screening women for ovarian cancer and have to share the disappointing news that it can’t. Here we dig into the reasons why, and what research is taking place in the search for a screening tool.

What is CA125?

CA125 is a protein that both women and men have in their blood. A high level of CA125 in your blood is a possible indicator of ovarian cancer, as CA125 can sometimes be produced by ovarian cancer cells. 

Why can't the CA125 blood test be used as a screening tool for ovarian cancer?

It is not just ovarian cancer that can cause an elevated CA125 reading, there are many other things that can cause this to be the case (a chest infection, pregnancy, endometriosis, or fibroids for example), along with the fact that some women will have a naturally elevated level with no cause for concern.

Not all women with a raised CA125 level will have ovarian cancer, and it is also important to consider some women may have ovarian cancer but have a normal CA125 reading.

Annually screening all women with a CA125 blood test could lead to many being referred for further investigations that are unnecessary, causing needless worry and the possibility of having to undergo inappropriate surgery for no reason.

In 2021 the results of a 20-year study looked at the effectiveness of CA125 blood tests and ultrasound scans as screening tests for ovarian cancer. The study concluded that using the CA125 blood test or ultrasound scans to test for ovarian cancer did not help people to live longer and are therefore not recommended to be used as screening tests for ovarian cancer.

What other research is happening in screening for ovarian cancer? 

Ovarian Cancer Action funds the work of Professor Ahmed at the University of Oxford and so far, the team have made several exciting discoveries that have taken them closer to answering that question. They have found that the number of cells that have a protein called SOX2 is markedly increased in the fallopian tubes of women with or at high risk of ovarian cancer. Having a better understanding of how the disease develops is key to developing a screening tool.

Although they have made some exciting discoveries, there is still a lot more research to be done. Identifying the SOX2 protein is an important step forward but it’s very difficult to get to, meaning a screening tool centred around it would be quite invasive. They are now looking for other changes that take place in the body simultaneously to the SOX2 protein production and, by harnessing different markers, they hope to find another marker that is easier to test for.

They hope to complete their next stage of investigations within the next five years and then the next step would be to translate their findings into clinical research.

All year round our scientists at the Ovarian Cancer Research Centre, The University of Oxford and beyond are working to find the next breakthrough in ovarian cancer research. Your donation will support the work they do each and every day. Donate now.