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5 May 2015, 18:58 | Updated: 5 May 2015, 19:01
Scientists say a blood test that's been found to correctly diagnose ovarian cancer in 86 per cent of women, after a trial led by University College London, is an "exciting breakthrough".
Research suggests a new screening test that tracks changing levels of a protein in the blood can detect twice as many ovarian cancers as conventional methods.
The technique relies on a statistical calculation to interpret variations in the level of a protein called CA125 which is linked to ovarian cancer.
It gives a more accurate prediction of risk than the traditional diagnostic blood test which uses a fixed cut-off point for CA125.
In the world's largest ovarian cancer screening trial, the new method correctly diagnosed 86% of women with invasive epithelial ovarian cancer (iEOC).
The standard test would have been expected to identify fewer than half these women, according to results from previous studies and clinical practice.
The 14-year UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS) led by University College London (UCL) recruited 202,638 post-menopausal women aged 50 and over who were randomly assigned different screening strategies.
Professor Usha Menon, UKCTOCS co-principal investigator and trial co-ordinator at UCL, said: "There is currently no national screening programme for ovarian cancer, as research to date has been unable to provide enough evidence that any one method would improve early detection of tumours.
"These results are therefore very encouraging. They show that use of an early detection strategy based on an individual's CA125 profile significantly improved cancer detection compared to what we've seen in previous screening trials.
"The numbers of unnecessary operations and complications were within acceptable limits and we were able to safely and effectively deliver screening for over a decade across 13 NHS Trusts. While this is a significant achievement, we need to wait until later this year when the final analysis of the trial is completed to know whether the cancers detected through screening were caught early enough to save lives."
The study, published in the Journal of Clinical Oncology, assessed 46,232 trial participants who continued to have regular screening checks after an initial test.
Their blood was tested once a year for CA125 levels and a computer programme used to predict the risk of ovarian cancer based on factors including age, the original level of the protein, and how that level changed over time.
Chief UKCTOCS investigator Professor Ian Jacobs, president of the University of New South Wales in Australia, who helped develop the statistical technique and conceived the trial, said: "CA125 as a biological marker for ovarian cancer has been called into question.
"Our findings indicate that this can be an accurate and sensitive screening tool, when used in the context of a woman's pattern of CA125 over time. What's normal for one woman may not be so for another. It is the change in levels of this protein that's important. My hope is that when the results of UKCTOCS are available this approach will prove capable of detecting ovarian cancer early enough to save lives."
In previous CA125 screening trials, some women with high levels of the protein were found to be free of ovarian cancer, while others with low levels harboured the disease.
The trial compared two diagnostic techniques, multimodal screening (MMS) involving the CA125 blood test and transvaginal ultrasound.
Further results from the ultrasound arm of the trial, and the impact of screening on cancer death rates, are expected later this year.
Dr James Brenton, ovarian cancer expert at Cancer Research UK, said: "A blood test to find women at risk of ovarian cancer is an exciting prospect, but this work still needs to be tested in women to see if it can save lives. By tracking how the levels of the CA125 protein change over time we might have an early signal to detect tumours. Ovarian cancer is particularly hard to spot at an early stage so it's vital that we find ways to diagnose the cancer sooner."
Athena Lamnisos, chief executive of the women's cancer charity The Eve Appeal, says: "The statistics around ovarian cancer are brutal and diagnosis often comes too late - either because a woman hasn't recognised the symptoms or because her GP doesn't.
"Our ambition is that this approach will be capable of detecting ovarian cancer at an earlier stage and save lives. These latest results are exciting and point towards the strides that we're making in more accurately predicting individual risk of developing cancer."