Natural history and screening model for high-risk human papillomavirus infection, neoplasia and cervical cancer in the Netherlands

Epidemiology of Cervical Cancer in the Caribbean

Cervical cancer (CvC) is considered a preventable disease; however, in the Caribbean, it is still one of the fourth most common causes of death in women. Efforts to overcome obstacles to the treatment and control of this preventable disease are being made by several countries within the Caribbean. However, no health issue can be readily managed without first acquiring an understanding of the dynamics relating to its severity of impact reaching the target population, its clinical pathology, and the availability of treatment and/or preventative measures to control or halt its progression. To assess the status of CvC in the Caribbean, a review of the literature was conducted using PubMed. The Caribbean was defined in the review as comprising nations and islands whose coastlines are touched by the Caribbean Sea. This led to an assessment of the available literature on CvC for 33 Caribbean territories. The review showed a lack of published information on CvC and highlights the need for greater research. This also serves as a template for subsequent investigations.

Estimating the conditional probability of developing human papilloma virus related oropharyngeal cancer by combining machine learning and inverse Bayesian modelling

The epidemic increase in the incidence of Human Papilloma Virus (HPV) related Oropharyngeal Squamous Cell Carcinomas (OPSCCs) in several countries worldwide represents a significant public health concern. Although gender neutral HPV vaccination programmes are expected to cause a reduction in the incidence rates of OPSCCs, these effects will not be evident in the foreseeable future. Secondary prevention strategies are currently not feasible due to an incomplete understanding of the natural history of oral HPV infections in OPSCCs. The key parameters that govern natural history models remain largely ill-defined for HPV related OPSCCs and cannot be easily inferred from experimental data. Mathematical models have been used to estimate some of these ill-defined parameters in cervical cancer, another HPV related cancer leading to successful implementation of cancer prevention strategies. We outline a "double-Bayesian" mathematical modelling approach, whereby, a Bayesian machine learning model first estimates the probability of an individual having an oral HPV infection, given OPSCC and other covariate information. The model is then inverted using Bayes' theorem to reverse the probability relationship. We use data from the Surveillance, Epidemiology, and End Results (SEER) cancer registry, SEER Head and Neck with HPV Database and the National Health and Nutrition Examination Surveys (NHANES), representing the adult population in the United States to derive our model. The model contains 8,106 OPSCC patients of which 73.0% had an oral HPV infection. When stratified by age, sex, marital status and race/ethnicity, the model estimated a higher conditional probability for developing OPSCCs given an oral HPV infection in non-Hispanic White males and females compared to other races/ethnicities. The proposed Bayesian model represents a proof-of-concept of a natural history model of HPV driven OPSCCs and outlines a strategy for estimating the conditional probability of an individual's risk of developing OPSCC following an oral HPV infection.

Reducing unnecessary referrals for colposcopy in hrHPV-positive women within the Dutch cervical cancer screening programme: A modelling study

BACKGROUND

With the implementation of primary high-risk human papillomavirus (hrHPV) screening in the Netherlands, an increase was observed in the number of unnecessary referrals (≤Cervical Intraepithelial Neoplasia (CIN) 1) to colposcopy. We aimed to investigate which alternative triage strategies safely reduce unnecessary referrals in HPV-based cervical cancer screening programmes.

METHODS

Microsimulation model MISCAN was used to simulate an unvaccinated cohort of ten million 30-year old Dutch women. We calculated unnecessary referrals, cervical cancer incidence, mortality, costs and QALYs for 24 triage strategies. Condition for direct referral (atypical squamous cells of undetermined significance (ASC-US), low-grade squamous intraepithelial lesions (LSIL), high-grade squamous intraepithelial lesions (HSIL), conditional on HPV-genotype 16/18/other high risk (OHR)), type of triage test (cytology alone or combined with hrHPV) and time to triage test (6 or 12 months) was varied.

RESULTS

The 24 triage strategies had varying effects on the number of unnecessary referrals ranging from -72% to +35%. Adjusting conditions for referral to 'HPV16/18+ and ASC-US+' and 'HPVOHR+ and HSIL+' and extending the interval between tests to 12 months resulted in a reduction in unnecessary referrals of 40% (incidence +0%, mortality -1%). Reduction in unnecessary referrals without genotyping was achieved by adjusting conditions for direct referral to LSIL (12 months to repeat test) (unnecessary referrals -37%, incidence +2%, mortality +0%).

CONCLUSIONS

To reduce the number of unnecessary referrals without increasing incidence and mortality by more than 2% in the Dutch cervical cancer screening programme, genotyping for HPV16 or HPV16/18 should be implemented with 12 months to repeat testing.

The advent of human papillomavirus detection for cervical screening

PURPOSE OF REVIEW

This review updates progress in the human papillomavirus (HPV)-based revolution in cervical screening and vaccination predicted to eventually eliminate cervical cancer.

RECENT FINDINGS

HPV PCR, patented by the author in 1987, has recently begun to replace cytology for primary cervical screening. I highlight the findings from large randomized clinical trials that have brought about this change, and progress with implementation. Australia was the first to introduce a national, publicly-funded HPV PCR-based program of primary screening, on 1 December 2017. The United Kingdom is set to follow, as are other countries. The widespread preference of self-sampling by under-screened women in particular will increase the effectiveness of population screening when using HPV tests. Coupled with improved vaccination now that more effective (nonavalent) HPV vaccines are being introduced, recent modeling predicts that cervical cancer will be markedly reduced, or even eliminated, in coming decades.

SUMMARY

The recent or pending change to more accurate cervical screening by HPV detection using PCR in various countries means less frequent screening for women. Women with an aversion to having their sample collected by a physician can collect their sample themselves, either at the doctor's rooms or at home, the sample then being mailed to the testing laboratory.

Transcriptome changes induced by RUNX3 in cervical cancer cells in vitro

Runt-related transcription factor 3 (RUNX3) is a member of Runt domain family that is known to play key roles in various different types of tumor. It was recently demonstrated that RUNX3 may also be associated with cervical cancer. The aim of the present study was to investigate the potential association between transcriptome changes and RUNX3 expression in cervical cancer. A RUNX3 overexpression model was constructed using cervical cancer cell lines by RUNX3 plasmid transfection. It was demonstrated that the upregulated expression of RUNX3 inhibited proliferation of cervical cancer cell lines, particularly SiHa cells, and was associated with the expression of the IL-6, PTGS2, FOSL1 and TNF genes. In addition, it was revealed that the TNF and FoxO pathways may also be affected by RUNX3. Therefore, the expression of the RUNX3 gene may be involved in the occurrence and progression of cervical cancer.

The health impact of human papillomavirus vaccination in the situation of primary human papillomavirus screening: A mathematical modeling study

BACKGROUND

Human papillomavirus (HPV) vaccination and the implementation of primary HPV screening in the Netherlands will lead to a lower cervical disease burden. For evaluation and further improvement of prevention, it is important to estimate the magnitude and timing of health benefits of current and alternative vaccination strategies such as vaccination of boys or adults.

METHODS AND FINDINGS

We evaluated the impact of the current girls-only vaccination program and alternative strategies on cervical disease burden among the first four vaccinated five-year birth cohorts, given the context of primary HPV screening. We integrated the existing microsimulation models STDSIM (HPV transmission model) and MISCAN-Cervix (cervical cancer screening model). Alternative vaccination strategies include: improved vaccination uptake, including routine boys vaccination, and offering adult vaccination at sexual health clinics. Our models show that the current vaccination program is estimated to reduce cervical cancers and cancer deaths by about 35% compared to primary HPV screening in the absence of vaccination. The number needed to vaccinate (NNV) to gain 1 life year is 45. The most efficient alternative vaccination strategies are: 1) improving coverage of girls to 80% (NNV = 42); and 2) routine vaccination for girls and boys at 80% coverage (incremental NNV = 155), with cervical cancer mortality reductions estimated at 50% and 60% respectively.

CONCLUSIONS

While the current program already substantially reduces cervical cancer incidence and mortality, prevention can be further improved by increasing vaccination uptake and extending vaccination to boys. As not all cervical cancer deaths will be prevented, screening participation should still be encouraged.

Cervical Cancer Screening in Partly HPV Vaccinated Cohorts - A Cost-Effectiveness Analysis

Background

Vaccination against the oncogenic human papillomavirus (HPV) types 16 and 18 will reduce the prevalence of these types, thereby also reducing cervical cancer risk in unvaccinated women. This (measurable) herd effect will be limited at first, but is expected to increase over time. At a certain herd immunity level, tailoring screening to vaccination status may no longer be worth the additional effort. Moreover, uniform screening may be the only viable option. We therefore investigated at what level of herd immunity it is cost-effective to also reduce screening intensity in unvaccinated women.

Methods

We used the MISCAN-Cervix model to determine the optimal screening strategy for a pre-vaccination population and for vaccinated women (~80% decreased risk), assuming a willingness-to-pay of €50,000 per quality-adjusted life year gained. We considered HPV testing, cytology testing and co-testing and varied the start age of screening, the screening interval and the number of lifetime screens. We then calculated the incremental cost-effectiveness ratio (ICER) of screening unvaccinated women with the strategy optimized to the pre-vaccination population as compared to with the strategy optimized to vaccinated women, assuming different herd immunity levels.

Results

Primary HPV screening with cytology triage was the optimal strategy, with 8 lifetime screens for the pre-vaccination population and 3 for vaccinated women. The ICER of screening unvaccinated women 8 times instead of 3 was €28,085 in the absence of herd immunity. At around 50% herd immunity, the ICER reached €50,000.

Conclusion

From a herd immunity level of 50% onwards, screening intensity based on the pre-vaccination risk level becomes cost-ineffective for unvaccinated women. Reducing the screening intensity of uniform screening may then be considered.

Cost-effectiveness analysis of human papillomavirus vaccination in South Africa accounting for human immunodeficiency virus prevalence

Background

This study aims at evaluating the cost-effectiveness of a 2-dose schedule human papillomavirus (HPV) vaccination programme of HPV and human immunodeficiency virus (HIV) naïve 12-year-old girls, in addition to cervical cancer (CC) screening alone, in South Africa. The study aims to account for both the impact of the vaccine among girls who are HIV-positive (HIV+) as well as HIV-negative (HIV-) population.

Methods

A previously published Markov cohort model was adapted to assess the impact and cost-effectiveness of a HPV vaccination programme in girls aged 12 years (N = 527 900) using the AS04-adjuvanted HPV-16/18 vaccine from a public payer perspective. Two subpopulations were considered: HIV- and HIV+ women. Each population followed the HPV natural history with different transition probabilities. Model input data were obtained from the literature, local databases and Delphi panel. Costs and outcomes were discounted at 5 %. Extensive sensitivity analyses were conducted to assess the robustness of the evaluation.

Results

Implementation of the AS04-adjuvanted HPV-16/18 vaccine in combination with current cytological screening in South African girls could prevent up to 8 869 CC cases and 5 436 CC deaths over the lifetime of a single cohort. Without discounting, this HPV vaccine is dominant over screening alone; with discounting, the incremental cost-effectiveness ratio is ZAR 81 978 (South African Rand) per quality-adjusted life years (QALY) gained. HPV vaccination can be considered cost-effective based on World Health Organization (WHO) recommended threshold (3 x gross domestic product/capita = ZAR 200 293). In a scenario with a hypothetical targeted vaccination in a HIV+ subpopulation alone, the modelled outcomes suggest that HPV vaccination is still cost-effective, although the incremental cost-effectiveness ratio increases to ZAR 102 479. Results were sensitive to discount rate, vaccine efficacy, HIV incidence and mortality rates, and HPV-related disease transition probabilities.

Conclusions

The AS04-adjuvanted HPV-16/18 vaccine can be considered cost-effective in a South African context although the cost-effectiveness is expected to be lower in the HIV+ subpopulation than in the overall female population. With improved access to HIV treatment, the HIV mortality and incidence rates are likely to be reduced, which could improve cost-effectiveness of the vaccination programme in South Africa.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-015-1295-z) contains supplementary material, which is available to authorized users.

Development of a quality framework for models of cervical screening and its application to evaluations of the cost-effectiveness of HPV vaccination in developed countries

BACKGROUND

HPV vaccination has now been introduced in most developed countries, but this has occurred in the context of established cervical cancer screening mechanisms which provide population-level protection against the most common HPV-related cancer. Therefore, estimating the cost-effectiveness of HPV vaccination to further reduce HPV-related disease depends in large part on the estimation of the effectiveness of the cervical screening 'background'. The aim of this study was to systematically review and assess methods for simulating cervical screening in decision analytic models used for evaluation of HPV vaccination.

METHODS

Existing quality frameworks for economic models were extended to develop a specific quality framework for models of cervical screening. This involved domains for model structure, parameterisation (data sources) and validation (consistency). A systematic review of economic evaluations of HPV vaccination was then conducted, and assessment of cervical screening model components was then performed via application of the new quality framework.

RESULTS

Generally, models took into account population-level cervical screening participation, but were inconsistent in their approach to modelling abnormal smear management, diagnostic evaluation and treatment of precancerous disease. There was also considerable variability in the accuracy of modelling clinical pathways and the scope of validation performed for screening-related outcomes, with focus directed towards cervical cancer targets. Only a few models comprehensively validated against observed pre-cancerous abnormalities.

CONCLUSION

Models of HPV vaccination in developed countries can be improved by further attention to the 'background' modelling of secondary protection via cervical screening. The quality framework developed for this review can be used to inform future HPV vaccination evaluations, including evaluations of the cost-effectiveness of male vaccination and next generation HPV vaccines, and to assess models used to evaluate new cervical screening technologies and recommendations.

Primary screening for human papillomavirus compared with cytology screening for cervical cancer in European settings: cost effectiveness analysis based on a Dutch microsimulation model

OBJECTIVES

To investigate, using a Dutch model, whether and under what variables framed for other European countries screening for human papillomavirus (HPV) is preferred over cytology screening for cervical cancer, and to calculate the preferred number of examinations over a woman's lifetime.

DESIGN

Cost effectiveness analysis based on a Dutch simulation model. Base case analyses investigated the cost effectiveness of more than 1500 different screening policies using the microsimulation model. Subsequently, the policies were compared for five different scenarios that represent different possible scenarios (risk of cervical cancer, previous screening, quality associated test characteristics, costs of testing, and prevalence of HPV).

SETTING

Various European countries.

POPULATION

Unvaccinated women born between 1939 and 1992.

MAIN OUTCOME MEASURES

Optimal screening strategy in terms of incremental cost effectiveness ratios (costs per quality adjusted life years gained) compared with different cost effectiveness thresholds, for two levels of sensitivity and costs of the HPV test.

RESULTS

Primary HPV screening was the preferred primary test over the age of 30 in many considered scenarios. Primary cytology screening was preferred only in scenarios with low costs of cytology and in scenarios with a high prevalence of HPV in combination with high costs of HPV testing.

CONCLUSIONS

Most European countries should consider switching from primary cytology to HPV screening for cervical cancer. HPV screening must, however, only be implemented in situations where screening is well controlled.

Long-term CIN3+ risk in women with abnormal cytology; role of hrHPV testing

Background:

Many studies have examined the short-term value of high-risk human papillomavirus (hrHPV) testing in predicting cumulative risk of cervical intraepithelial neoplasia grade 3 or cancer (CIN3+). This study focuses on long-term CIN3+ risk after initial wait and see policy.

Methods:

A total of 342 women with abnormal cytology of borderline/mild dyskaryosis (BMD) or worse (>BMD), included between 1990 and 1992, were followed-up by cytology and hrHPV testing until 1996 and monitored by cytology thereafter. Primary endpoint was cumulative CIN3+ risk by December 2009.

Results:

Women with BMD had a 5-year CIN3+ risk of 22.5% (95% confidence interval (CI) 17.0–29.1) and of 0.7% (0.1–4.5) in the subsequent 5 years. High-risk human papillomavirus-negative women with BMD had a 5-year risk of <0.01% (95% CI 0.0–5.1) and of <0.01% (0.0–5.7) in the following 5 years, while for hrHPV-positive women these risks were 37.5% (29.0–46.9) and 1.6% (0.2–9.5), respectively. Women with >BMD had a 5-year risk of 45.1% (36.4–54.1) and of 3.5% (0.9–12.2) in the subsequent 5 years. High-risk human papillomavirus-negative women with >BMD had a 5-year risk of 7.3% (2.0–23.6) and hrHPV-positive women of 56.6% (46.4–66.3).

Conclusion:

Women with BMD have an elevated CIN3+ risk for 5 years only; afterwards their risk is similar to the general population. High-risk human papillomavirus-negative women with BMD may return to regular screening directly. All other women with ⩾BMD should be referred for additional testing and/or colposcopy.

Incorporating calibrated model parameters into sensitivity analyses: deterministic and probabilistic approaches

OBJECTIVE

The aim of this study was to examine how calibration uncertainty affects the overall uncertainty of a mathematical model and to evaluate potential drivers of calibration uncertainty.

METHODS

A lifetime Markov model of the natural history of human papillomavirus (HPV) infection and cervical disease was developed to assess the cost effectiveness of a hypothetical HPV vaccine. Published data on cervical cancer incidence and mortality and prevalence of pre-cursor lesions were used as endpoints to calibrate the age- and HPV-type-specific transition probabilities between health states using the Nelder-Mead simplex method of calibration. A conventional probabilistic sensitivity analysis (PSA) was performed to assess uncertainty in vaccine efficacy, cost and utility estimates. To quantify the uncertainty around calibrated transition probabilities, a second PSA (calibration PSA) was performed using 25 distinct combinations of objective functions and starting simplexes.

RESULTS

The initial calibration produced an incremental cost-effectiveness ratio (ICER) of $US 4300 per QALY for vaccination compared with no vaccination, and the conventional PSA gave a 95% credible interval of dominant to $US 9800 around this estimate (2005 values). The 95% credible interval for the ICERs in the calibration PSA ranged from $US 1000 to $US 37,700.

CONCLUSIONS

Compared with a conventional PSA, the calibration PSA results reveal a greater level of uncertainty in cost-effectiveness results. Sensitivity analyses around model calibration should be performed to account for uncertainty arising from the calibration process.

Long-term impact of human papillomavirus vaccination on infection rates, cervical abnormalities, and cancer incidence

BACKGROUND

Vaccination against human papillomavirus (HPV) types 16/18 is being implemented in many countries. There may be indirect benefit of HPV vaccination to nonvaccinated women, who may experience a reduced risk of infection with vaccine-preventable types (herd immunity). We attempt to disentangle the direct and indirect effects of HPV vaccination, while accounting for 14 oncogenic HPV types in a dynamic modeling framework.

METHODS

On the basis of vaccine uptake among preadolescent girls in the Netherlands, we calculated how heterosexual transmission of HPV-16/18 is expected to change as a result of vaccination, and used these predictions in an individual-based simulation model of cervical carcinogenesis that considers 14 high-risk HPV types. Models were parameterized to match prevaccine data on type-specific HPV infection and cervical disease.

RESULTS

At 50% vaccine coverage, the estimated lifetime infection risk in nonvaccinated women dropped from 0.46 (95% credible interval = 0.35-0.54) to 0.37 (0.26-0.46) for HPV-16, and from 0.40 (0.32-0.46) to 0.31 (0.22-0.36) [corrected] for HPV-18. For the whole population, we calculated an eventual 47% reduction in cervical cancer incidence, with 1 in 4 cases prevented among nonvaccinated women. The number of indirectly averted cancer cases was highest with vaccine coverage between 50% and 70%, approximating 70 cases per 100,000 women born from 2010 onward.

CONCLUSIONS

HPV-16/18 vaccination of preadolescent girls will markedly lower infection rates among nonvaccinated women. Reduced transmission of vaccine-preventable HPV becomes a prominent aspect of cervical cancer control, especially in populations with moderate vaccine coverage.

Epidemiologic natural history and clinical management of Human Papillomavirus (HPV) Disease: a critical and systematic review of the literature in the development of an HPV dynamic transmission model

BACKGROUND

Natural history models of human papillomavirus (HPV) infection and disease have been used in a number of policy evaluations of technologies to prevent and screen for HPV disease (e.g., cervical cancer, anogenital warts), sometimes with wide variation in values for epidemiologic and clinical inputs. The objectives of this study are to: (1) Provide an updated critical and systematic review of the evidence base to support epidemiologic and clinical modeling of key HPV disease-related parameters in the context of an HPV multi-type disease transmission model which we have applied within a U.S. population context; (2) Identify areas where additional studies are particularly needed.

METHODS

Consistent with our and other prior HPV natural history models, the literature review was confined to cervical disease and genital warts. Between October 2005 and January 2006, data were gathered from the published English language medical literature through a search of the PubMed database and references were examined from prior HPV natural history models and review papers. Study design and data quality from individual studies were compared and analyses meeting pre-defined criteria were selected.

RESULTS

Published data meeting review eligibility criteria were most plentiful for natural history parameters relating to the progression and regression of cervical intraepithelial neoplasia (CIN) without HPV typing, and data concerning the natural history of HPV disease due to specific HPV types were often lacking. Epidemiologic evidence to support age-dependency in the risk of progression and regression of HPV disease was found to be weak, and an alternative hypothesis concerning the time-dependence of transition rates is explored. No data were found on the duration of immunity following HPV infection. In the area of clinical management, data were observed to be lacking on the proportion of clinically manifest anogenital warts that are treated and the proportion of cervical cancer cases that become symptomatic by stage.

CONCLUSION

Knowledge of the natural history of HPV disease has been considerably enhanced over the past two decades, through the publication of an increasing number of relevant studies. However, considerable opportunity remains for advancing our understanding of HPV natural history and the quality of associated models, particularly with respect to examining HPV age- and type-specific outcomes, and acquired immunity following infection.

HPV16/18 vaccination to prevent cervical cancer in The Netherlands: model-based cost-effectiveness

We evaluated the cost-effectiveness of HPV16/18 vaccination for girls aged 12 years in The Netherlands in addition to cervical cancer screening. For this purpose, we developed a simulation model that describes the relation between each of the high-risk human papillomavirus (hrHPV) types and cervical disease, allowing the occurrence of multiple type-specific infections. Model parameters were derived from Dutch cohort studies, including a large population-based screening trial, and from the national cervical cancer registry. The model satisfactorily reproduced Dutch data on HPV infection and the presence of cervical lesions. For our base-case scenario in which 85% of the girls aged 12 years were vaccinated against types 16/18 (95% efficacy, lifelong protection), the model predicted a decrease of 60% in the number of cervical cancer cases and cervical cancer deaths indicating that substantial health benefits can be achieved. Health savings were robust against changes in the vaccine efficacy (varied from 85% to 98%) but savings showed a substantial reduction when the efficacy started waning 10 years after vaccination. The discounted costs per quality-adjusted life year (QALY) were euro 19,500/QALY (range euro 11,000 to euro 25,000/QALY) and lied near the cost-effectiveness threshold of euro 20,000/QALY used in The Netherlands. The simulations further showed that vaccination cannot replace screening because vaccination without screening was less effective than screening in preventing cancer in women over 40 years of age. In conclusion, our model results support the implementation of HPV16/18 vaccination in young women in addition to cervical cancer screening.

Calibration methods used in cancer simulation models and suggested reporting guidelines

Increasingly, computer simulation models are used for economic and policy evaluation in cancer prevention and control. A model's predictions of key outcomes, such as screening effectiveness, depend on the values of unobservable natural history parameters. Calibration is the process of determining the values of unobservable parameters by constraining model output to replicate observed data. Because there are many approaches for model calibration and little consensus on best practices, we surveyed the literature to catalogue the use and reporting of these methods in cancer simulation models. We conducted a MEDLINE search (1980 through 2006) for articles on cancer-screening models and supplemented search results with articles from our personal reference databases. For each article, two authors independently abstracted pre-determined items using a standard form. Data items included cancer site, model type, methods used for determination of unobservable parameter values and description of any calibration protocol. All authors reached consensus on items of disagreement. Reviews and non-cancer models were excluded. Articles describing analytical models, which estimate parameters with statistical approaches (e.g. maximum likelihood) were catalogued separately. Models that included unobservable parameters were analysed and classified by whether calibration methods were reported and if so, the methods used. The review process yielded 154 articles that met our inclusion criteria and, of these, we concluded that 131 may have used calibration methods to determine model parameters. Although the term 'calibration' was not always used, descriptions of calibration or 'model fitting' were found in 50% (n = 66) of the articles, with an additional 16% (n = 21) providing a reference to methods. Calibration target data were identified in nearly all of these articles. Other methodological details, such as the goodness-of-fit metric, were discussed in 54% (n = 47 of 87) of the articles reporting calibration methods, while few details were provided on the algorithms used to search the parameter space. Our review shows that the use of cancer simulation modelling is increasing, although thorough descriptions of calibration procedures are rare in the published literature for these models. Calibration is a key component of model development and is central to the validity and credibility of subsequent analyses and inferences drawn from model predictions. To aid peer-review and facilitate discussion of modelling methods, we propose a standardized Calibration Reporting Checklist for model documentation.

Structural differences among cost-effectiveness models of human papillomavirus vaccines

In this article we compare previously published cost-effectiveness studies of human papillomavirus (HPV) vaccines along a defined subset of key model structural assumptions relating to HPV infection and disease, cervical cancer screening and HPV vaccination. For each structural aspect examined, we summarize assumptions from each study, provide a critical review and discuss the impact upon results. Considerable variation was observed across HPV vaccine cost-effectiveness models in a number of influential assumptions. Holding constant factors for which current data are lacking, the combined impact of assumptions made for the remaining parameters examined would appear to tend toward underestimation of the cost-effectiveness of HPV vaccination within existing studies. However, uncertainty concerning parameters, such as the duration of vaccine protection and acquired immunity following HPV infection, and the relationship between age and HPV virulence, complicates precise estimation of the cost-effectiveness of HPV vaccination and rigorous evaluation of the validity of existing modeling results.

Long-term clinical impact of introducing a human papillomavirus 16/18 AS04 adjuvant cervical cancer vaccine in Spain

BACKGROUND

Human papillomavirus (HPV) epidemiology and screening practices vary considerably between countries and specific analyses are required to estimate the impact of HPV vaccination. This study aimed to predict the clinical benefits of introducing a bivalent HPV16/18 vaccine in Spain, where the cervical cancer (CC) incidence is 10.3 per 100 000.

METHODS

A Markov model based upon the natural history of HPV and CC was developed to simulate transitions between health states, in the presence of specific screening programmes. Published data were used to reflect the Spanish situation in terms of epidemiological characteristics, screening and treatment practices. Calibration consisted of varying disease progression rates within established ranges until model predictions matched observed epidemiological data. The clinical impact of vaccinating a cohort of 12-year-old girls against HPV was assessed over their lifetime using the calibrated model.

RESULTS

Vaccination of all 12-year-old girls would result in a reduction of 75% (from 0.32% to 0.08%) in the prevalence of high-grade precancerous lesions due to oncogenic HPV, and a 79% reduction in both CC cases (from 1745 to 365) and CC deaths (from 417 to 86). Assuming a vaccine coverage of 80%, the number of CC cases and deaths would decrease by 63%. Vaccination could also substantially reduce the number of screening tests and treatments required for cervical dysplasia.

CONCLUSION

Our model was successfully adapted to the Spanish epidemiological environment, screening and treatment practices and predicted a substantial long-term benefit of HPV vaccination despite a low HPV prevalence in Spain.

Assessing the introduction of universal human papillomavirus vaccination for preadolescent girls in The Netherlands

A persistent infection with human papillomavirus (HPV) is a prerequisite for the development of cervical cancer. Clinical trials with HPV-vaccines have been very successful in preventing persistent HPV16/18 infections, the two most oncogenic HPV-genotypes. We assessed the introduction of universal HPV-vaccination for preadolescent girls in the Dutch National Immunization Programme. Long-term vaccine efficacy, the need and extent of a catch-up programme for young women, and the impact of vaccination on the cervical cancer screening programme are major unresolved issues. Preliminary conservative estimates (80% vaccine efficacy and no effects on the screening programme, transmission rate, non-cervical cancer incidence, and cross protection) predict an acceptable cost-effectiveness ratio for universal vaccination of preadolescent girls.

Cost-effectiveness of human papillomavirus testing after treatment for cervical intraepithelial neoplasia

OBJECTIVE

To compare current cytological follow up of women treated for high-grade cervical intraepithelial neoplasia (CIN) with follow up by high-risk human papillomavirus (HPV) testing together with cytology.

DESIGN

A cost-effectiveness modelling study.

SETTING

Gynaecology clinics in the Netherlands.

POPULATION

Women treated for high-grade CIN.

METHODS

A Markov model was developed to compare six follow-up strategies with HPV testing with current cytological follow up at 6, 12, and 24 months. Model parameter estimation was based on three Dutch follow-up studies and a Dutch population-based screening cohort.

MAIN OUTCOME MEASURES

The number of CIN2/3 cases missed after 5 years follow up, the number of diagnostic procedures, and costs involved.

RESULTS

Strategies with adjunct HPV testing were more effective than current follow up (reduction in missed CIN2/3 cases 32-77%, corresponding to a number needed to treat of 192-455) and less inconvenient (reduction in repeat smears 28-65%). A particularly attractive strategy was HPV testing alone at 6 months and both HPV and cytological testing at 24 months after treatment. This strategy yielded a high detection rate of post-treatment CIN, did not lead to an increase in colposcopy rate, and was 49 Euro per woman cheaper than the current strategy.

CONCLUSIONS

Our model supports the use of high-risk HPV testing for monitoring women treated for high-grade CIN.

An appraisal of the level of awareness and utilization of the Pap smear as a cervical cancer screening test among female health workers in a tertiary health institution

Papanicolaou (Pap) smear test is considered the best approach to reduce cervical cancer incidence worldwide. We surveyed 195 female health workers with structured questionnaires to identify factors that could influence the awareness and utilization of the Pap smear as a cervical cancer screening test. More than 65% of the respondents were aware of the disease, cervical cancer, and approximately 64% were aware of the Pap smear test. Seven three (39.7%) of the respondents had their sexual debut (coitarche) before the age of 20 years, while 109 (59.9%) have had multiple sexual partners. The modal number of sexual partners was 3, range 0-8. Pap smear awareness level significantly varied among the categories of the female health workers (P < 0.001). A minority of 14.1% have had a Pap test. There was a significant variation in utilization of Pap test across the various categories of the health workers (Pearson Chi-square 14.67, P < 0.05), and a significant correlation between Pap smear awareness and utilization (P < 0.001). The majority, 89%, believed that they were not at risk of developing cervical cancer. The self-reported utilization of Pap test among health workers was low. While there was a positive correlation between Pap test awareness and utilization, screening uptake was very poor due to a combination of inappropriate beliefs, misapprehension, and deficient knowledge. There is an urgent need for an aggressive awareness campaign and the provision of a screening program nationally.

Cervical screening in the 21st century: the case for human papillomavirus testing of self-collected specimens

Cervical screening by Pap smear involves a high rate of false negatives, necessitating frequent testing. Because women do not like the sampling procedure, many avoid being screened. Testing for the causative high-risk human papillomavirus (HPV) types, by PCR or other technologies, on self-collected (tampon) samples permits women to be monitored non-invasively. The high negative predictive value of HPV testing means a greater interval between tests, and thus reduces costs. HPV testing lends itself to primary screening. A kit for self-collection and return to a testing laboratory, followed by practitioner notification and follow-up if required, should result in wider participation. The higher accuracy of HPV testing should lead to improved cervical cancer prevention.

Detection and typing of 46 genital human papillomaviruses by the L1F/L1R primer system based multiplex PCR and hybridization

There are several genital HPV DNA detection systems described, however most of them present different disadvantages regarding the number of amplified and detected types, sensitivity, type specificity. A new PCR and hybridization based detection method was developed for sensitive and balanced amplification and specific typing of HPV DNA from clinical samples. The technique amplifies and detects 46 HPV types: 2a, 3, 6, 7, 10, 11, 13, 16, 18, 26, 27, 28, 29, 30, 31, 33, 34, 35, 39, 40, 42, 43, 44/55, 45, 51, 52, 53, 54, 56, 57, 58, 59, 61, 66, 67, 68, 70, 72, 73(MM9), 74, 82(MM4), 84(MM8), 89, 90, 91. Key elements of the L1F/L1R PCR and hybridization system are: the special selection of the amplified region, a novel and optimized amplification primer set, circumspectly designed general and type-specific oligonucleotide probes. Detection following a multiplex PCR is based on solid phase hybridization in microtiter plate format using general and type-specific probes at medium stringency, which makes the detection robust in case of small sequence variations. The assay is highly reproducible and suitable for automation. The method was compared to Hybrid Capture II test, and after clarifying conflicting results, the comparison showed an excellent agreement (96.2%).

Evaluation of cervical screening strategies with adjunct high-risk human papillomavirus testing for women with borderline or mild dyskaryosis

The management of women with a smear read as borderline/mild dyskaryosis (BMD) found by cervical cancer screening is still under discussion as only few of these cases are associated with high-grade lesions. To determine the optimal screening strategy for these women, a simulation model of cervical cancer development was used that is based on high-risk human papillomavirus (hrHPV) infection. The current strategy of repeat cytological testing at 6 and 18 months after BMD was compared to strategies with adjunct hrHPV testing. Calculations were done for both conventional and liquid-based cytology as the primary screening tool. In comparison to current screening, adjunct hrHPV testing was more effective in preventing cancer and more woman-friendly (reduction in colposcopy referrals with outcome < cervical intraepithelial neoplasia (CIN2) of up to 56% and in repeat smears of 30-100%). In combination with conventional cytology, cost-effective strategies were the ones in which a sample for high-risk human papillomavirus (hrHPV) testing is collected at a return visit within 1 month or in which hrHPV testing is restricted to repeat smears taken at 6 and 18 months. For these strategies, co-collection of samples for hrHPV testing at baseline is not necessary which has organizational and cost advantages. In combination with liquid-based cytology, it was cost-effective to perform a reflex hrHPV test at baseline from the liquid-based specimen. Liquid-based screening was more effective than conventional screening, but annual diagnosis costs were euro5 million higher (population size 16 million). In conclusion, our calculations indicate that implementation of hrHPV testing for the management of women with borderline or mild dyskaryosis (BMD) is feasible both in settings where conventional and liquid-based cytology is current practice.

Preferential risk of HPV16 for squamous cell carcinoma and of HPV18 for adenocarcinoma of the cervix compared to women with normal cytology in The Netherlands

We present the type-distribution of high-risk human papillomavirus (HPV) types in women with normal cytology (n=1467), adenocarcinoma in situ (ACIS) (n=61), adenocarcinoma (n=70), and squamous cell carcinoma (SCC) (n=83). Cervical adenocarcinoma and ACIS were significantly more frequently associated with HPV18 (OR_MH 15.0; 95% CI 8.6–26.1 and 21.8; 95% CI 11.9–39.8, respectively) than normal cytology. Human papillomavirus16 was only associated with adenocarcinoma and ACIS after exclusion of HPV18-positive cases (OR_MH 6.6; 95% CI 2.8–16.0 and 9.4; 95% CI 2.8–31.2, respectively). For SCC, HPV16 prevalence was elevated (OR_MH 7.0; 95% CI 3.9–12.4) compared to cases with normal cytology, and HPV18 prevalence was only increased after exclusion of HPV16-positive cases (OR_MH 4.3; 95% CI 1.6–11.6). These results suggest that HPV18 is mainly a risk factor for the development of adenocarcinoma whereas HPV16 is associated with both SCC and adenocarcinoma.