HPV test may prevent more cervical cancers than cytology alone
Human papillomavirus (HPV) testing could be used as the standard method of cervical screening for women aged 35 years or older, as it seems to prevent more invasive cases of the disease than cytology screening alone, Italian scientists have said.
The New Technologies for Cervical Cancer (NTCC) screening study, led by Guglielmo Ronco from the Centre for Cancer Prevention in Turin, looked at the benefits and risks of introducing HPV testing in cervical cancer screening.
DNA testing for HPV is already known to be more sensitive than cytology screening at detecting abnormal cells called high-grade cervical intraepithelial neoplasia (CIN2 and CIN3). If left untreated, these cells could develop into cervical cancer. In cytology screening, often called a smear test, cells are observed under a microscope to look for any abnormalities.
But HPV testing is less specific and generates more 'false-positive' tests, where the result is positive but, on further investigation, there are no abnormal cells or invasive cancer.
For this reason, scientists were unsure whether switching from 'smear' tests to HPV testing would actually increase the effectiveness of cervical cancer screening programmes in preventing invasive disease.
Dr Ronco's team, including Cancer Research UK's Professor Jack Cuzick based at Queen Mary, University of London, recruited women between the ages of 25 and 60 in two recruitment phases into a cytology group and a HPV group.
The researchers found that during the first round of screening, nine invasive cancers were detected in the cytology group and seven in the HPV group, meaning that the two tests identified a similar number of cancers.
But in the second round, no invasive cancers were detected in the HPV group compared with nine in the cytology group.
This indicates that HPV-based screening is more effective at preventing invasive cervical cancer, probably thanks to earlier detection of abnormal cells which could develop into cancer if left untreated.
The researchers also noted that combining HPV testing with cytology did not improve the sensitivity of screening in over-35s, suggesting that increased detection of abnormal cells was due to HPV testing alone.
In women between the ages of 25 and 34, however, HPV testing was associated with over-diagnosis and unnecessary treatment as abnormal cells in this age group can be more likely to disappear of their own accord in time.
Writing in the Lancet Oncology, the researchers said that their data "support the use of stand-alone HPV testing as the primary screening test" at "extended intervals".
They added: "Further follow-up is needed to define how long screening intervals can be safely extended. Research is needed to define the optimum management of HPV-positive women ... to minimise the costs related to increased referral to colposcopy and over-diagnosis of regressive lesions."
Writing in an accompanying comment, Philip Castle and Hormuzd Katki, from the National Cancer Institute in the US, said that HPV testing shows "a great deal of promise to revolutionise cervical cancer screening" but there is room for improvement and a need for further research.
Dr Lesley Walker, director of cancer information at Cancer Research UK, said: "Cervical screening looks for changes in the cells of the cervix before a cancer has developed. This research suggests that by testing for HPV in women aged 35 and over we might be able to spot the warning signs even earlier and it might, in future, mean that women go for screening less often. But it's important to note that for women under 35, HPV testing often leads to over-diagnosis of abnormal changes that will clear up by themselves."