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What has happened to the world's largest ovarian cancer screening trial?

13 May 2021

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Why was this trial so important?

Women with ovarian cancer have the lowest chance of survival compared to other gynaecological cancers, with most women still being diagnosed at an advanced stage. If a woman’s ovarian cancer is diagnosed at stage 1 she has a 90% chance of surviving for five years or more but by stage 4 survival rate is as low as 4%. The chance of survival dramatically increases for women diagnosed at the earliest stage, which has motivated researchers and clinicians over decades to find a way to screen for ovarian cancer. Screening programmes have dramatically improved survival rates for other cancers such as cervical and breast cancer, however there are currently no such successful screening methods available for ovarian cancer.

What did the trial involve?

The UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS) based at University College London was looking to see if population screening using a combination of CA125 testing and transvaginal ultrasound can reduce deaths from ovarian cancer. The trial included over 200,000 healthy post menopausal women from across England, Wales, and Northern Ireland recruited over four years. 

What did the trial show?

Long term follow up of participants over 16 years has shown that these screening approaches did not significantly reduce the chance of these women developing late stage ovarian cancer. Unfortunately, this means that these tests cannot be recommended as a screening programme for the public.

The results did show that the CA125 blood test picked up more cancers at an early stage compared to both the women that received ultrasound screening and the women that received no screening. However, this did not show a reduction in deaths in the follow up of the blood test group.

What does this mean for the possibility of a screening tool for ovarian cancer?

This trial has provided a step forward in the development of a screening tool for ovarian cancer by showing us what doesn’t work. There is still hope for developing a screening tool for ovarian cancer, and the results of this trial shows that, like in cervical cancer screening, we need to find a way to detect ovarian cancer before it has developed. Tests like CA125 and ultrasound can pick up established cancers, however it may be too late in the disease course to be able to treat these successfully that will result in an increased chance of survival. 

What screening research is Ovarian Cancer Action supporting? 

Ovarian Cancer Action funded researcher Professor Ahmed Ahmed and his team from the University of Oxford want to fill in the gaps of knowledge that up until now have prevented the development of a screening tool. The team are looking to find how healthy cells become cancerous in ovarian cancer, and how these pre-cancerous lesions can be detected. 

They have already found the majority of ovarian cancers start in the Fallopian tube and have discovered six previously unknown cell types which are ‘mirrored’ into different types of ovarian cancer. This is an important step in identifying the pre-cancerous cell of origin in ovarian cancer. The team are now working to see what are the stages of how these cells turn cancerous, to bring us one step closer to finding a screening tool for ovarian cancer. 

Another of our funded researchers Dr Jon Krell at Imperial College London is looking into more targeted strategies for screening those at the highest risk. He has developed an ovarian cancer risk calculator which uses genetic and lifestyle information from women to calculate their personalised risk score for ovarian cancer. Their aim is to use this information to help guide screening and prevention measures by identifying women most at risk to help detect ovarian cancer earlier or stop it from developing in the first instance.

Ovarian Cancer Action CEO Cary Wakefield says: “Research showing us what doesn't work is as valuable as showing us what does. While these results are disappointing, they have shown how important further research is to develop a screening tool for the next generation that detects ovarian cancer at its earliest stages. That is exactly what we are still determined to do."

Ovarian Cancer Action Head of Policy and Research Marie-Claire Platt says “Today we are thanking the amazing 200,000 healthy women who volunteered to take part in this research. They should all be proud of their invaluable contribution to a vision of an ovarian cancer screening tool for the next generation”. 

Find out more about the research that Dr Jon Krell and Professor Ahmed Ahmed are working on.