A new test for cervical cancer outperforms both the current Pap smear and human papillomavirus (HPV) test at a reduced cost, according to a new Canadian study.
Researchers investigated how well the epigenetics-based test predicted the development of cervical cancer, up to five years in advance, in a clinical trial of more than 15,000 women aged 25 to 65 years.
As opposed to checking for patterns in the DNA genetic code that are indicative of the HPV virus, the new test looks at the naturally-occurring chemical markers that appear on top of the DNA, making up its 'epigenetic profile'. The test picks up epigenetic changes.
"In contrast to what most researchers and clinicians are saying, we are seeing more and more evidence that it is in fact epigenetics, and not DNA mutations, that drives a whole range of early cancers, including cervical, anal, oropharyngeal, colon, and prostate cancer," said lead researcher Attila Lorincz, who helped develop the world’s first test for HPV in 1988.
Epigenetic changes are caused by changes in gene expression (active versus inactive genes), rather than alteration of the underlying genetic code.
Screening to prevent cervical cancer is typically done through the Pap smear, which involves collection, staining and microscopic examination of cervical cells. Pap smear can only detect 50 per cent of cervical pre-cancers.
The HPV test that tests for the presence of DNA from the human papillomavirus, which causes cervical cancer, is more accurate, but it only identifies whether or not women are infected with a cancer-causing HPV, but not their actual risk of cancer. This causes unnecessary worry for the majority of HPV-infected women who receive a positive result, but will eventually clear the virus and not develop the disease.
The new test detected 100 per cent of the eight invasive cervical cancers that developed during the trial. In comparison, the Pap smear only detected 25 per cent of the cancers, and the HPV test detected 50 per cent.
The study also looked more closely at a subset of 257 HPV-positive women, who were representatively selected from the large study.
The new test detected 93 per cent of pre-cancerous lesions in those women, compared to 86 per cent detected using a combination of the Pap smear and HPV test, and 61 per cent detected using the Pap smear on its own.
"We were surprised by how well this new test can detect and predict early cervical cancers years in advance, with 100 per cent of cancers detected, including adenocarcinomas, a type of cervical cancer that is very difficult to detect,” said Professor Lorincz, adding that the new test could take up to five years to become available.
The authors say that this test would reduce the number of doctor visits and screening appointments, as high-grade disease would be detected from the start. It would also be cheaper than the Pap smear.
The findings were published in the International Journal of Cancer.