Primary screening for HPV (human papillomavirus) provides 60% to 70% greater protection against invasive cervical cancer than the cytology-based (smear test) screening currently used in most countries where cervical screening is available, according to a new study.
Cervical screening aims to prevent invasive cervical cancer by detecting abnormalities in a woman’s cervix, which can be a precursor to cancer. In cytology-based screening, the cells taken during the test are examined under a microscope to detect changes. In HPV-based screening, the cells are initially tested for the presence of HPV, a common and usually harmless viral infection. Some cases of HPV can cause the abnormalities in the cervix which can precede cancer. In both cases, if cell changes or HPV are detected, the patient is notified, and undergoes further screening and examination, followed by treatment, if needed.
The research team, Guglielmo Ronco, MD, of the Center for Cancer Epidemiology and Prevention in Turin, Italy, analyzed data from four major European trials in England, Italy, the Netherlands, and Sweden. These trials compared HPV-based screening with cytology-based screening. In all of the trials, researchers examined the effectiveness of HPV or cytological screening in detecting precursors for treatment to prevent progression to cancer. However, until now, no study could provide reliable estimates of the effectiveness of HPV versus cytological screening in protecting against invasive cervical cancer.
By following more than 175,000 women age 20 to 64 years who participated in the four trials for an average of 6.5 years, the researchers were able to show that detection of invasive cancers was similar between screening methods for the first 2.5 years after the trials began. Thereafter, fewer cancers were detected in women who had undergone HPV screening, with the researchers calculating that HPV-based screening protected 60% to 70% more women from invasive cervical cancer than did cytology-based screening. The study was published in The Lancet (2013; doi:10.1016/S0140-6736(13)62218-7).
Despite the fact that each of the trials included in the analysis used different screening protocols, the efficacy of HPV testing was not notably different across the trials. Moreover, the results show that increased protection against invasive cervical cancer was especially notable in women age 30 to 35 years, and HPV screening every 5 years was most protective against invasive cancers of the cervix, compared with cytology done every 3 years.
Ronco explained, “Our analysis shows that HPV-based screening appears to prevent more invasive cervical cancers than does cytology. On this basis, we recommend implementation of HPV-based cervical screening with triage from age 30 years at intervals of at least 5 years. Triage means that HPV-positive women have a follow-up cytology test (reflex cytology) and only those with abnormal cytology or persistent HPV infection go on to have colposcopy.”