Cervical cancer prevention in Australia: Planning for the future

The high rate of coverage that has been achieved to date by the Australian government's Human Papillomavirus (HPV) Vaccination Program has already led to profound reductions in the prevalence of biopsy-confirmed, high-grade abnormalities and of vaccine-preventable HPV types in Australia. Declines in the prevalence of vaccine preventable HPV have occurred not only in vaccinated women but also in unvaccinated women, suggesting a herd-immunity affect. These declines were anticipated on the basis of modelling and were the major drivers for the changes proposed to the Australian National Cervical Screening Program. The federal and state-based Australian governments established a "Renewal Steering Committee," which conducted a literature search and a review of the available evidence to assess its applicability and quality. Together with this information the committee also used modeling to determine the optimal screening pathway for cervical cancer screening and constructed a plan for implementing the changes that will be required to transition from the currently successful screening program to the renewed program. The committee recommended that Australia move to a screening program based on testing every 5 years using an HPV test with partial genotyping with reflex liquid-based cytology (LBC) triage for HPV-vaccinated and unvaccinated women ages 25 to 69 years, and an additional exit test for women up to age 74 years. Primary HPV testing and reflex LBC will be funded by government. Symptomatic women outside the screening program will also be able to access government funded testing. The new screening program, to be rolled out in 2017, will also provide a cost-effective framework for an evaluation of the national HPV vaccination program, enabling ongoing monitoring of HPV genotypes and cervical lesions in screened women.

Impact of a population-based HPV vaccination program on cervical abnormalities: a data linkage study

BACKGROUND

Australia was one of the first countries to introduce a publicly funded national human papillomavirus (HPV) vaccination program that commenced in April 2007, using the quadrivalent HPV vaccine targeting 12- to 13-year-old girls on an ongoing basis. Two-year catch-up programs were offered to 14- to 17- year-old girls in schools and 18- to 26-year-old women in community-based settings. We present data from the school-based program on population-level vaccine effectiveness against cervical abnormalities in Victoria, Australia.

METHODS

Data for women age-eligible for the HPV vaccination program were linked between the Victorian Cervical Cytology Registry and the National HPV Vaccination Program Register to create a cohort of screening women who were either vaccinated or unvaccinated. Entry into the cohort was 1 April 2007 or at first Pap test for women not already screening. Vaccine effectiveness (VE) and hazard ratios (HR) for cervical abnormalities by vaccination status between 1 April 2007 and 31 December 2011 were calculated using proportional hazards regression.

RESULTS

The study included 14,085 unvaccinated and 24,871 vaccinated women attending screening who were eligible for vaccination at school, 85.0% of whom had received three doses. Detection rates of histologically confirmed high-grade (HG) cervical abnormalities and high-grade cytology (HGC) were significantly lower for vaccinated women (any dose) (HG 4.8 per 1,000 person-years, HGC 11.9 per 1,000 person-years) compared with unvaccinated women (HG 6.4 per 1,000 person-years, HGC 15.3 per 1,000 person-years) HR 0.72 (95% CI 0.58 to 0.91) and HR 0.75 (95% CI 0.65 to 0.87), respectively. The HR for low-grade (LG) cytological abnormalities was 0.76 (95% CI 0.72 to 0.80). VE adjusted a priori for age at first screening, socioeconomic status and remoteness index, for women who were completely vaccinated, was greatest for CIN3+/AIS at 47.5% (95% CI 22.7 to 64.4) and 36.4% (95% CI 9.8 to 55.1) for women who received any dose of vaccine, and was negatively associated with age. For women who received only one or two doses of vaccine, HRs for HG histology were not significantly different from 1.0, although the number of outcomes was small.

CONCLUSION

A population-based HPV vaccination program in schools significantly reduced cervical abnormalities for vaccinated women within five years of implementation, with the greatest vaccine effectiveness observed for the youngest women.

Early effect of the HPV vaccination programme on cervical abnormalities in Victoria, Australia: an ecological study

BACKGROUND

Australia introduced a human papillomavirus (HPV) vaccination programme with the quadrivalent HPV vaccine for all women aged 12-26 years between 2007 and 2009. We analysed trends in cervical abnormalities in women in Victoria, Australia, before and after introduction of the vaccination programme.

METHODS

With data from the Victorian Cervical Cytology Registry between 2003 and 2009, we compared the incidence of histopathologically defined high-grade cervical abnormalities (HGAs, lesions coded as cervical intraepithelial neoplasia of grade 2 or worse or adenocarcinoma in situ; primary outcome) and low-grade cytological abnormalities (LGAs) in five age groups before (Jan 1, 2003, to March 31, 2007) and after (April 1, 2007, to Dec 31, 2009) the vaccination programme began. Binary comparisons between the two periods were done with Fisher's exact test. Poisson piecewise regression analysis was used to compare incident rate trends.

FINDINGS

After the introduction of the vaccination programme, we recorded a decrease in the incidence of HGAs by 0·38% (95% CI 0·61-0·16) in girls younger than 18 years. This decrease was progressive and significantly different to the linear trend in incidence before introduction of the vaccination (incident rate ratio 1·14, 1·00-1·30, p=0·05). No similar temporal decline was recorded for LGAs or in older age groups.

INTERPRETATION

This is the first report of a decrease in incidence of HGAs within 3 years after the implementation of a population-wide HPV vaccination programme. Linkage between vaccination and screening registers is needed to confirm that this ecological observation is attributable to vaccination and to monitor participation in screening among vaccinated women.

FUNDING

None.

Effect of study design and quality on unsatisfactory rates, cytology classifications, and accuracy in liquid-based versus conventional cervical cytology: a systematic review

BACKGROUND

Liquid-based cytology is reported to increase the sensitivity of cervical cytology and the proportion of slides that are satisfactory for assessment, in comparison with conventional cytology. Although some countries have changed to liquid-based cytology for cervical screening, controversy remains. We reviewed the published work to assess the performance of liquid-based cytology relative to conventional cytology in primary studies assessed to be of low, medium, or high methodological quality.

METHODS

56 primary studies were reviewed and assessed with strict methodological criteria. Liquid-based cytology and conventional cytology were compared in terms of the percentage of slides classified as unsatisfactory, the percentage of slides classified in each cytology category, and the accuracy of detection of high-grade disease. Data were examined for studies overall and in strata to examine the effect of study quality on results.

FINDINGS

The median difference in the percentage of unsatisfactory slides between liquid-based cytology and conventional cytology was 0.17%. Only one small study was a randomised controlled trial. The classification of high-grade squamous epithelial lesion varied according to study quality (p=0.04), with conventional cytology classifying more slides in this category than did liquid-based cytology in high-quality studies (n=3) only. In medium-quality (n=30) and high-quality studies, liquid-based cytology classified more slides as atypical squamous cells of unknown significance than did conventional cytology when compared with low-quality studies (n=17; p=0.05). Only four studies provided sufficient verified data to allow estimation of sensitivity and specificity and comparison of test accuracy.

INTERPRETATION

We saw no evidence that liquid-based cytology reduced the proportion of unsatisfactory slides, or detected more high-grade lesions in high-quality studies, than conventional cytology. This review does not lend support to claims of better performance by liquid-based cytology. Large randomised controlled trials are needed.