A study found that testing women for the Human Papilloma Virus (HPV) is more effective in protecting against invasive cervical cancer than traditional cytology (the smear test).
In the analysis of 176,000 women participating in longitudinal trials in England, Italy, the Netherlands and Sweden, the overall detection rate was found to be higher in those women who had been tested for HPV compared to those who had smear tests. Study participants were followed for an average of 6.5 years following their HPV or cytology test. 107 invasive cervical carcinomas (cancers) were identified.
The study recommends HPV testing being used as a primary screening tool for cervical cancer and highlights the potential economies of scale in replacing the 3 yearly smear test with a 5 yearly HPV test – increasing accuracy, reducing costs.
In the UK, only women who have been identified with abnormal cytology results have an HPV test. The HPV test is not currently a primary screening tool.
Invasive cervical cancer is a cancer that spreads from the surface of the cervix to tissue deeper in the cervix or other parts of the body. The American Cancer Society predicts that in 2013 as many as 12,340 new cases of invasive cervical cancer will be diagnosed and 4,030 women will die from cervical cancer.
HPV “V” Cytology
There was no difference in the accuracy of HPV and cytology tests within the the first 2.5 years after the HPV screen or smear test. After a period of 3.5 years, the detection rates differed significantly between HPV and the smear test, even more so after 5.5 years.
After an initial negative smear test the cumulative incidence of invasive cervical cancer was
- 15.4 per 100000 women after 3.5 years
- 36 per 100 000 after 5.5 years
Among women who had a negative HPV test the cumulative incidence of invasive cervical cancer was
- 4.6 per 100 000 after 3.5 years
- 8.7 per 100 000 after 5.5 years
Lead researcher, Guglielmo Ronco from Italy’s Center for Cancer Epidemiology and Prevention, said,
Our analysis shows that HPV based screening appears to prevent more invasive cervical cancers than does cytology, and on this basis we recommend implementation of HPV based cervical screening with triage from age 30 years at intervals of at least five years.
Margaret Stanley, professor of epithelial biology at the University of Cambridge, added that because HPV DNA testing was more sensitive than the smear test, more women were directed to colposcopy and more pre-cancers were detected and treated and more invasive cancers prevented.
However, she noted that smear tests would remain the primary screening test in the UK until the current cohort of women who have had the HPV vaccine come through.
Vaccination against HPV has been available in the UK for girls aged 12-13 years since 2008.
In a commentary on the analysis, Sandra Isidean and Eduardo Franco of McGill University commented,
The future of cervical cancer screening in high-resource settings will most probably incorporate primary HPV testing, a science-driven change in strategy that particularly befits the post-HPV vaccination era.
When the vaccinated cohorts reach screening age—25 in England—then HPV testing will have to be the screening method, since most of the dangerous pre cancers caused by HPV16 and 18 will have been prevented, and the Pap smear test will lose its specificity.”
BMJ: HPV screening offers greater protection against invasive cervical cancer than cytology, finds analysis – http://www.bmj.com/content/347/bmj.f6624
Image credit: with thanks to Vierdrie of RGB Free Stock