MADRID, (EUROPA PRESS). – A total of 17 genotypes of the human papillomavirus (HPV) cause invasive cervical cancer, but with enormous differences in their carcinogenic strength, according to a new systematic analysis carried out by scientists from the International Agency for Research on Cancer (IARC), which belongs to the World Health Organization (WHO).
The study, published in The Lancet, is based on a novel methodology that compares HPV genotypes in more than 110,000 women with cervical cancer with those of more than 2.5 million women without cancer (controls).
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Their objective was to evaluate which HPV genotypes caused cancer, as well as their carcinogenic potential and their contribution to the burden of cervical cancer.
“This study represents the most comprehensive attempt to date to estimate the proportion of invasive cervical cancer caused by different HPV genotypes at global, regional and national levels,” said Gary Clifford, deputy head of IARC’s Early Detection, Prevention and Infections Branch and senior author on the paper.
“These findings directly inform strategies for the prevention of invasive cervical cancer, emphasizing targeted approaches through HPV vaccination and screening,” she noted.
THE RESULTS
In the analysis, 17 HPV genotypes were considered to be causative of invasive cervical cancer, but with enormous differences in their carcinogenic strength.
HPV types 16 and 18 caused approximately three-quarters of cervical cancer cases in all regions of the world. HPV types 31, 33, 45, 52 and 58 contributed to an additional 15-20 percent of cases.
The remaining 10 causative genotypes caused only about 5 percent of cases worldwide, with some notable regional variations, including a higher proportion (4%) for HPV 35 in Africa than in other regions.
The eight HPV genotypes with the highest attributable fractions (HPV types 16, 18, 31, 33, 35, 45, 52, and 58) were also the most carcinogenic and are therefore also clear priority targets for inclusion in HPV-based screening tests.
Other HPV genotypes, each of which causes only a small fraction of invasive cervical cancer cases, have a lower positive predictive value. Including these genotypes in cervical cancer screening tests makes screening less effective and less cost-effective.
“These data suggest that future HPV vaccines could target HPV 35 to reduce regional disparities,” said Dr. Clifford. “Effective and equitable cervical cancer prevention could be achieved by targeting at least the eight major HPV types in vaccines and diagnostics, especially in resource-limited regions where the burden is greatest.”
Currently, in Spain, the ‘Gardasil 9’ vaccine helps prevent infection by the same 4 types of HPV as ‘Gardasil’ plus 5 other types of viruses considered high risk: 31, 33, 45, 52 and 58.
