HPV screen up to 70% better than smear test at warding off cancer

HPV screen up to 70% better than smear test at warding off cancer

National screening programmes should switch to the HPV test, and at extended intervals of five years, rather than the current three, recommend the researchers.


During a smear test, the swabbed cervical cells are examined under a microscope to detect pre-cancerous changes. In HPV screening, the cells are initially tested for the presence of HPV, the common viral infection, certain types of which are linked to an increased risk of cervical cancer.


A team of Italian researchers analysed data from four major European trials in England (ARTISTIC), Italy (NTCC), the Netherlands (POBASCAM), and Sweden (Swedescreen) which compared the effectiveness of HPV-based screening with cytology-based screening to prevent progression to cancer.


By tracking the subsequent health of more than 175 000 women aged 20–64 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, and the researchers calculated that HPV-based screening protected 60–70% more women from invasive cervical cancer than did the smear test.


Despite the fact that each of the trials included in the analysis used different screening protocols, the efficacy of HPV testing was not markedly different.


Furthermore, the results showed that increased protection against invasive cervical cancer was especially notable in women aged 30–35 years, and that HPV screening every 5 years was most protective against invasive cancers of the cervix, compared with cytology done every 3 years.


“Until now, there have been no direct estimates of the relative efficacy of HPV-based versus cytology-based screening for prevention of invasive cancer in women who undergo regular screening, of how variables like age affect this efficacy, and of the duration of protection,” comments lead researcher Dr Guglielmo Ronco, from the Center for Cancer Epidemiology and Prevention in Turin, Italy.


“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 5 years,” he adds.


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.


In a linked comment, Sandra Isidean and Eduardo Franco of McGill University in Montreal, Canada, write that the future of cervical cancer screening in developed countries will most probably incorporate primary HPV testing.


“With economies of scale that come with broad implementation of primary HPV testing (which will foster competition among various HPV tests) and the lengthening of screen intervals, cervical cancer screening might end up costing countries less money while providing greater safety than with conventional cervical cytology,” they write.


But nations would need to consider important logistical challenges, including settling on the type of HPV screening test to be used; ascertaining appropriate screening ages and intervals; defining triage and management policies for HPV-positive women; and ensuring quality of and adherence to revised policies, they suggest.



By Caroline White


OnMedica, Monday, 4 November 2013




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