Cervical cancer screening is in the news, with some headlines saying that a new test can detect the disease 100% of the time and could ‘revolutionise screening’.
But while the test itself could provide a new option for detecting changes to cells in the cervix, the reality is the test is a long way from being routinely used. And based on the research published so far, it’s not yet known if the new test is better than those that are already used.
What is the new test?
Scientists from Queen Mary University of London, funded by the Canadian Institutes for Health Research and Cancer Research UK, developed a new test that can pick up changes in chemical ‘tags’ that sit on top of DNA in cells, called epigenetic changes. The changes can control how the DNA in cells is read and how cells behave.
And lead researcher on the latest study, Professor Attila Lorincz, believes that because epigenetic changes play a key role in certain cancers, a test that picks up these changes could one day help detect these diseases.
By detecting epigenetic changes, the team’s new test is different from those currently used in cervical cancer screening, which look for the presence of human papillomavirus (HPV) DNA in cells and at changes in cervical cells under the microscope (also known as cytology).
And in their latest study, published in the International Journal of Cancer, the scientists were exploring if their new test could be more effective at picking up up pre-cancerous changes in women who had tested positive for HPV than current techniques.
What did the study find?
The study used samples taken during a cervical cancer screening trial that included 15,744 women. The original trial wasn’t evaluating the benefits of the new cervical cancer test, but the researchers used 257 samples from that trial to see how their new test fared against HPV testing and looking at cells under the microscope. All 257 samples had already tested positive for the presence of HPV.
The new test correctly found the most advanced pre-cancerous cell changes in 93 in 100 samples on average, compared with 86 in 100 advanced pre-cancerous cell changes that were detected using a combination of HPV testing and cytology. Based on statistical tests, the researchers couldn’t rule out whether or not this difference was just down to chance.
Of the 15,744 women on the original trial, 8 went on to develop invasive cervical cancer during the trial. Researchers ran samples taken at the beginning of the trial from these 8 women and found that all 8 samples carried signs of the epigenetic changes picked up by the test, whereas the HPV test only found virus DNA in 4 of the samples.
How do you assess a cancer test?
Researchers look at 3 main things when assessing a new diagnostic test.
- Sensitivity – the probability that you test positive if you have the disease.
- Specificity – the probability that you test negative if you do not have the disease.
- Accuracy – the proportion of samples correctly classified by the test. It’s a combined measure of sensitivity and specificity.
While the results for the new test looks promising, it’s hard to get too excited until the results are repeated in a larger group of women.
And the test would need to be compared to the current methods for screening for cervical cancer, to help researchers assess if the new test is more sensitive and specific than existing techniques.
It’s always exciting to see new methods being developed that could one day be used to improve cervical cancer diagnosis and prevention through screening. But the reality is there’s a long way to go before we’ll know if this method will be accurate enough to replace the tests already used in the UK’s cervical screening programme.
Cook, et al. (2018) Evaluation of a validated methylation triage signature for human papillomavirus positive women in the HPV FOCAL cervical cancer screening trial. International Journal of Cancer. DOI: 10.1002/ijc.31976
Tanya Klymenko December 20, 2018