HPV prevalence in screened population and types associated with cervix disease

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Published: 13 Nov 2013
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Dr Lesley Anderson - Queens University, Belfast, UK

Dr Lesley Anderson talks to ecancertv at the UK's National Cancer Research Institute ( NCRI ) 2013 meeting about a study looking at the changing profile of HPV infection and resultant disease now that the UK has introduced an HPV vaccine.

This study aimed to determine the prevalence of HPV infection among screening age women prior to vaccination and determine HPV types associated with cervix disease.

HPV positivity was investigated using the Roche Cobas 4800 in 5557 eligible Liquid Based Cytology (LBC) samples from women of screening age in Northern Ireland and 2048 samples of cervical pathology collected prospectively.

LBC samples revealed a crude age standardised prevalence of high risk HPV of 17.4% in screening age women in Northern Ireland. The highest rate (42.5%) was in those aged 20-24. HPV prevalence by main subtypes were: HPV 16 (5.3%) 31 (2.5%) 51 (2.2%) 18 (1.7%). For cervical pathology prevalence of HPV was 64.7% overall, increasing from 48.1% of CINI, 65.7% of CINII, 81.3% of CINIII to 89.1% of cervical squamous cell carcinomas (SCC). The majority of SCC's tested positive for HPV16 or 18 (91.2% of HPV positive samples). HPV positivity was found in 92.9% microinvasive SCC, 50% of adenocarcinomas, 66.7% adenosquamous carcinomas, 88.2% cervical glandular intraepithelial neoplasia and 29.1% koilocytosis. The number of genotypes detected varied across pathology grade, On average 2.5 genotypes where detected per positive sample. A trend was identified that CIN I had the lowest percentage (66.0%) of single genotypes. On average 91.8% of all cancerous samples containing only one HPV genotype. The most frequent single genotypes found in cancerous samples were HPV16, HPV18, HPV45, HPV31, HPV39 and HPV52.

For SCC samples not testing positive for HPV16 or HPV 18, five samples tested positive for a single HPV 31, HPV 39, HPV 45 or HPV 52 genotype, which may have implications for vaccine cross protection of non-target genotypes as these types are common in women with normal cervical pathology.

We undertook initially the first study which was conducted throughout 2009 and it was looking at the HPV genotypes that were present within the cervical smears that had been taken of women of screening age in Northern Ireland, so at that time it was women between the ages of 20 and 64. Within that study what we identified was that around a third of women in the age group of 20-24 years had a high risk human papilloma virus present within their cervical sample. The rate of high risk HPV decreased with increasing age which is consistent with the literature which suggests that some HPV types remain prevalent in certain women and others regress.

So within the first study we looked at 6,000 women and within those we identified 13% overall that had high risk human papilloma virus. We also conducted a systematic review of the literature looking across the UK at other studies and our results fitted in fairly well with the other studies across the United Kingdom. The main type that we found within the cervical samples was HPV16 which the current vaccination programme covers. We also found other high risk HPV genotypes including 52, 59, 31 and others and HPV18 was present but in a smaller proportion of women within Northern Ireland.

The implication of it is that there are a large number of women within the population that do have high risk human papilloma virus. We also then looked in the second study at women who had cervical disease, that was right through from cervical intraepithelial neoplasia 1 through to cervical cancer. In those types we found HPV16 was the most common type in women who developed cervical cancer but we also identified HPV52, 45, 35 and 18 as being implicated in cervical cancer within Northern Ireland.

So the current vaccination programme covers the majority of types of HPV that are implicated in the development of cervical disease, however, there are other HPV types that aren’t within the vaccine that it does not cover. So it is therefore important that women, including those who have been vaccinated and also those who are not vaccinated, if they’re invited to go for a cervical smear that they attend.

Do we need another vaccine?

Yes, at the minute there are a number of companies that are undertaking to try and develop polyvalent vaccines, so vaccines that cover additional types on top of the four that are currently covered in the current vaccine and that these may be region specific, so there do appear to be differences between the UK and elsewhere in the world. So this information that we’ve collected as part of this study and other studies within the UK will be really important in trying to determine which HPV vaccination type we should use.