Mathematical model for the natural history of human papillomavirus infection and cervical carcinogenesis

Human papillomavirus vaccine and cervical cancer prevention

Cervical cancer is one of the most common types of cancer in women worldwide, with the highest rates observed in underdeveloped countries. In the last decades, its incidence has decreased after the implementation of screening programs, mainly in developed countries. Infection with high-risk oncogenic HPV is associated with precancerous lesions and cervical cancer. Advances in the understanding of the role of HPV in the etiology of high-grade cervical lesions (CIN 2/3) and cervical cancer have led to the development, evaluation and recommendation of two prophylactic HPV vaccines. This review article provides a summary of the studies related with their development and efficacy.

HPV infection in women: psychosexual impact of genital warts and intraepithelial lesions

INTRODUCTION

Genital Human Papillomavirus (HPV) infection is the most commonly occurring sexually transmitted viral infection in humans. HPV is a wide family of DNA viruses, which may cause benign skin and mucosal tumors (genital, anal, or oral warts), intraepithelial neoplasias, and/or malignant cancers in different organs. Women are more susceptible to the oncogenic effect of HPVs, mostly at the genital site on the uterine cervix.

AIMS

This review analyzes the impact of: (i) genital warts (GWs) and their treatment; (ii) HPV-related genital, oral, and anal precancerous lesions on women's sexual function.

METHODS

A Medline search was carried out. Search terms were HPV, GWs, intraepithelial neoplasia, cervical cancer, anal cancer, oral cancer, epidemiology, HPV risk factors, sexual dysfunctions, desire disorders, arousal disorders, dyspareunia, vulvar vestibulitis, vulvodynia, orgasmic difficulties, sexual repertoire, couple sexual problems, depression, anxiety, pap smear, screening program, therapy, and vaccines.

MAIN OUTCOME MEASURES

Sexual consequences of HPV infection in women, specifically GWs and intraepithelial HPV-related neoplasia.

RESULTS

Psychosexual vulnerability increases with number of recurrences of HPV infections. Depression, anxiety, and anger are the emotions most frequently reported. However, to date, there is no conclusive evidence of a specific correlation between HPV infection and a specific female sexual disorder. The relationship between HPV and vulvar vestibulitis/vulvodynia-related dyspareunia seems not to be direct. Counseling problems, the role of anti-HPV vaccine, and the concept of the high-risk partner are discussed. The reader is offered a practical approach with clinically relevant recommendations that may prove useful in his/her daily practice when dealing with HPV-infected women and couples.

CONCLUSION

The evidence of psychosexual consequences of HPV-related GWs and intraepithelial lesions is limited. Specific research on the sexual impact of GWs and intraepithelial HPV-related lesion in women is urgently needed.

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.

Cost-effectiveness evaluation of a quadrivalent human papillomavirus vaccine in Belgium

BACKGROUND

The introduction of a quadrivalent human papillomavirus (HPV; types 6, 11, 16, 18) vaccine is expected to significantly reduce the burden of cervical cancer, cervical intraepithelial neoplasia (CIN), genital warts and other HPV-related diseases.

OBJECTIVE

To determine the cost effectiveness of providing a quadrivalent (6,11,16,18) HPV vaccine programme in adolescent females aged 12 years in addition to the existing cervical cancer screening programme in Belgium.

METHODS

A Markov state-transition model was developed for the Belgian context in order to evaluate the long-term impact of vaccinating a cohort of girls aged 12 years alongside the existing screening programme. Women were followed until the age of 85 years. A vaccine that would prevent 100% of diseases associated with HPV-6, -11, -16 and -18, with lifetime duration of efficacy, 80% coverage, in conjunction with current screening, was compared with screening alone. For this analysis, 35% of cases of CIN-1, 55% of CIN-2/3, 75% of cervical cancer and 90% of genital warts were considered to be attributable to HPV-6, -11, -16 or -18. The model estimated lifetime risks and total lifetime healthcare costs, survival and QALYs for cervical cancer, CIN and genital warts. Outcomes validation was applied. Model outcomes also included incremental costs per life-year gained and incremental costs per QALY gained. The analysis was conducted from the perspective of the Belgian healthcare payer, and costs were in year 2006 values.

RESULTS

The model estimated a reduction in the lifetime risk of cervical cancer from 0.94% to 0.34%, therefore preventing 362 cases of cervical cancer and 131 related deaths in a cohort of 60,000 girls aged 12 years in Belgium. The base-case scenario suggests quadrivalent HPV vaccination in addition to current cervical screening in Belgium to be cost effective at euro 10,546 per QALY. This is within the accepted range of cost-effective interventions in Europe. This cost effectiveness is maintained for different parameter assumptions in the sensitivity analysis, with the exception of very high discount rates for costs and medical benefits, but, even in the worst case, ratios were still less than euro 50,000 per QALY. Even when a separate scenario modelled the requirement for a booster vaccination to sustain a lifetime duration of protection, the results remained cost effective at eruo 17,388 per QALY.

CONCLUSIONS

Vaccination with a quadrivalent HPV vaccine appears to be a cost-effective public health intervention in conjunction with the existing screening programme in Belgium. The additional costs of introducing vaccination to the established screening programme would be offset by the potential savings from not having to treat the diseases caused by HPV-6, -11, -16 or -18.

A review of prophylactic human papillomavirus vaccines: recommendations and monitoring in the US

It has been estimated that genital human papillomavirus (HPV) is the most common sexually transmitted infection in the US. Nononcogenic types, such as HPV type 6 (HPV-6) and HPV-11, can cause benign or low-grade cervical cell changes, genital warts, and recurrent respiratory papillomatosis. Oncogenic types can cause cervical and other anogenital cancers; oncogenic HPV types are detected in 99% of cervical cancers worldwide. A quadrivalent HPV vaccine to prevent HPV-6, HPV-11, HPV-16, and HPV-18 was licensed for use in the US in June 2006 and an application for Food and Drug Administration licensure was submitted for a bivalent HPV vaccine to prevent HPV-16 and HPV-18 in March 2007. Currently in the US, the quadrivalent HPV vaccine is recommended for routine immunization of girls aged 11 and 12 years, and catch-up immunization is recommended through age 26 years. Monitoring the impact of prophylactic HPV vaccines will be useful for understanding the population level impact of vaccination. In this report, the authors provide a brief review of the epidemiology of HPV infection and an overview of prophylactic HPV vaccines and postvaccine licensure monitoring.

Cost effectiveness of high-risk HPV DNA testing for cervical cancer screening in South Africa

OBJECTIVE

To determine the cost effectiveness of several cervical cancer screening strategies utilizing HPV testing in South Africa.

METHODS

We developed a lifetime Markov model of the costs, quality of life, and survival associated with screening and treating cervical cancer and its precursors. Screening strategies evaluated included: 1) conventional cytology, 2) cytology followed by HPV testing for triage of equivocal cytology, 3) HPV testing, 4) HPV testing followed by cytology for triage of HPV-positive women, and 5) co-screening with cytology and HPV testing. Primary outcome measures included quality-adjusted life-years saved (QALYs), incremental cost-effectiveness ratios, and lifetime risk of cervical cancer. Costs are in 2006 South African Rand (R).

RESULTS

In a cohort of 100,000 women, starting at age 30 and screening once every 10 years reduced the lifetime risk of cervical cancer by 13-52% depending on the screening strategy used, at an incremental cost of R13,000-R42,000 per QALY. When strategies were compared incrementally, cytology with HPV triage was less expensive and more effective than screening using cytology alone. HPV testing with the use of cytology triage was a more effective strategy and costs an additional R42,121 per QALY. HPV testing with colposcopy for HPV-positive women was the next most effective option at an incremental cost of R1541 per QALY. Simultaneous HPV testing and cytology co-screening was the most effective strategy and had an incremental cost of R25,414 per QALY.

CONCLUSIONS

In our model, HPV testing to screen for cervical cancer and its precursors is a cost-effective strategy in South Africa.

Health and economic impact associated with a quadrivalent HPV vaccine in Italy

OBJECTIVE

The aim of this study was to determine the health impact and cost-effectiveness of introducing a human papillomavirus (HPV) vaccination programme with a quadrivalent vaccine alongside the existing cervical cancer screening programme in comparison to the current context in Italy.

METHODS

A US Markov model was adapted to the Italian context, assuming under base case 80% vaccine coverage rate, lifetime duration of protection in a cohort of girls aged 12 years and discount rates of 1.5% and 3% for health benefits and costs, respectively, and estimating direct medical costs.

RESULTS

The HPV vaccination in association with the current screening programme would allow to avoid 1432 cases of cervical cancer (-63.3%) and 513 deaths (-63.4%) compared to screening only, with an incremental cost-effectiveness ratio (ICER) of 9569 euros per additional quality-adjusted life-year (QALY) gained. The sensitivity analysis highlighted that this model was robust to all parameters presenting uncertainties as the ICERs ranged from 2,781 euros to 48,122 euros per QALY gained.

CONCLUSION

This study showed that HPV vaccination in adolescent girls would be a beneficial and cost-effective public health programme in Italy.

A multi-type HPV transmission model

A prophylactic quadrivalent (types 6/11/16/18) vaccine against oncogenic and warts-causing genital Human papillomavirus (HPV) types was approved by the US Food and Drug Administration in 2006. This paper presents a nonlinear, deterministic, age-structured, mathematical model of the transmission dynamics of HPV and disease occurrence in a US population stratified by gender and sexual activity group. The model can assess both the epidemiologic consequences and cost effectiveness of alternative vaccination strategies in a setting of organized cervical cancer screening in the United States. Inputs for the model were obtained from public data sources, published literature, and analyses of clinical trial data. The results suggest that a prophylactic quadrivalent HPV vaccine can: (i) substantially reduce the incidence of disease, (ii) increase survival among females, (iii) improve quality of life for both males and females, (iv) be cost-effective when administered to females age 12-24 years, and (v) be cost-effective when implemented as a strategy that combines vaccination of both females and males before age 12 vaccination with a 12 to 24 years of age catch-up vaccination program.

Updated guidelines for papanicolaou tests, colposcopy, and human papillomavirus testing in adolescents

Worldwide, cervical cancer is a major health concern for women of all ages; however the epidemiology and biology of human papillomavirus (HPV) infection differs in female adolescents and adults. In the United States, 50% of adolescent and young women acquire HPV within 3 years after initiating sexual intercourse, resulting in relatively high prevalence rates. Most infections, however, are transient and clear within several months. Consequently HPV infections detected in adolescents are likely to reflect benign disease, whereas infections detected in older women are likely to reflect persistent infections and a higher risk of advanced cervical intraepithelial lesions that can lead to invasive cervical cancer. This article reviews the most recently published guidelines for the prevention of cervical cancer through screening and management of abnormal cervical cytologic and histologic findings, which have been updated to reflect the differences in HPV infections and cervical abnormalities in female adolescents and adults.

Sexually transmitted infections and pelvic inflammatory disease in women

Sexually transmitted infections (STIs) are an important public health challenge in the United States. Primary care clinicians can contribute to decreasing these largely preventable causes of morbidity and mortality by integrating routine screening, testing, counseling, treatment, and partner management of STIs into their practice. Newer tests for chlamydia and gonorrhea that can be performed on urine specimens allow screening without a pelvic examination. The most recent edition of the Centers for Disease Control and Prevention sexually transmitted disease treatment guidelines provides an evidence-based, reliable, and convenient set of recommendations for treating and caring for patients who have STIs.

Reducing ovarian cancer mortality through screening: Is it possible, and can we afford it?

OBJECTIVE

Ovarian cancer is a leading cause of cancer-related deaths among women. Given the low prevalence of this disease, the effectiveness of screening strategies has not been established. We wished to estimate the clinical impact and cost-effectiveness of potential screening strategies for ovarian cancer using population-specific data.

METHODS

A Markov state transition model to simulate the natural history of ovarian cancer in a cohort of women age 20 to 100. Age-specific incidence and mortality rates were obtained from SEER. Base-case characteristics of a potential screening test were sensitivity 85%, specificity 95%, and cost $50. Outcome measures were mortality reduction, lifetime number of false positive screening tests, positive predictive value, years of life saved (YLS), lifetime costs in US dollars, and incremental cost-effectiveness ratios (ICER, in cost/YLS).

RESULTS

Model-predicted lifetime risk of ovarian cancer (1.38%), lifetime risk of death from ovarian cancer (0.95%), and stage distribution (stage I-19%; stage II-7%; stage III, IV, or unstaged - 74%) closely approximated SEER data. Annual screening resulted in 43% reduction in ovarian cancer mortality, with ICER of $73,469/YLS (base case) and $36,025/YLS (high-risk population) compared to no screening. In the base case, the average lifetime number of false positive tests is 1.06. Cost-effectiveness of screening is most sensitive to test frequency, specificity and cost.

CONCLUSIONS

Annual screening for ovarian cancer has the potential to be cost effective, particularly in high-risk populations. Clinically acceptable positive predictive values are achieved if specificity exceeds 99%. Mortality reduction above 50% may not be achievable without screening intervals less than 12 months.

Cost-effectiveness analysis of adding a quadrivalent HPV vaccine to the cervical cancer screening programme in Switzerland

OBJECTIVE

Based on positive safety and efficacy data, a quadrivalent Human PapillomaVirus (HPV) vaccine has been approved in Switzerland to prevent HPV types 6, 11, 16 and 18 infections. The objective of this study was to explore the cost-effectiveness of an HPV vaccination in Switzerland.

DESIGN AND METHODS

A Markov model of the natural history of HPV infection was adapted to the Swiss context and followed a hypothetical cohort of 41,200 girls aged 11 years over their lifetime. Main epidemiological and economic parameters were extracted from the literature. Two strategies were compared: conventional cytological screening only and HPV vaccination followed by conventional cytological screening. A coverage rate of 80% was used and the vaccine was assumed to provide a lifelong protection. Analyses were performed from the direct health care cost perspective including only direct medical costs.

RESULTS

Compared to screening only, adding a quadrivalent HPV vaccine could prevent over lifetime 62% of cervical cancers and related deaths, 19% of Cervical Intraepithelial Neoplasia (CIN 1), 43% of CIN 2, 45% of CIN 3 and 66% of genital warts per cohort. Incremental cost-effectiveness ratios (ICER) were estimated to be CHF 45,008 per Life Year Gained (LYG) and CHF 26,005 per Quality Adjusted Life Year (QALY) gained. Sensitivity analyses demonstrated that the ICER was robust to all parameters, but was most sensitive to the need for a booster and discount rates.

CONCLUSIONS

Compared to commonly accepted standard thresholds in Europe and other vaccination strategies implemented in Switzerland, adding a quadrivalent HPV vaccine alongside the current cervical cancer screening programme is likely to be cost-effective in Switzerland.

Adding a quadrivalent human papillomavirus vaccine to the UK cervical cancer screening programme: A cost-effectiveness analysis

BACKGROUND

We assessed the cost-effectiveness of adding a quadrivalent (6/11/16/18) human papillomavirus (HPV) vaccine to the current screening programme in the UK compared to screening alone.

METHODS

A Markov model of the natural history of HPV infection incorporating screening and vaccination was developed. A vaccine that prevents 98% of HPV 6, 11, 16 and 18-associated disease, with a lifetime duration and 85% coverage, in conjunction with current screening was considered.

RESULTS

Vaccination with screening, compared to screening alone, was associated with an incremental cost-effectiveness ratio of pound21,059 per quality adjusted life year (QALY) and pound34,687 per life year saved (LYS). More than 400 cases of cervical cancer, 6700 cases of cervical intraepithelial neoplasia and 4750 cases of genital warts could be avoided per 100,000 vaccinated girls. Results were sensitive to assumptions about the need for a booster, the duration of vaccine efficacy and discount rate.

CONCLUSION

These analyses suggest that adding a quadrivalent HPV vaccine to current screening in the UK could be a cost-effective method for further reducing the burden of cervical cancer.

Cost-effectiveness analysis of the introduction of a quadrivalent human papillomavirus vaccine in France

Objectives:A vaccine to prevent diseases due to human papillomavirus (HPV) types 6, 11, 16, and 18 is now available in France. The objective of this study was to assess the health and economic impact in France of implementing a quadrivalent HPV vaccine alongside existing screening practices versus screening alone.

Methods:A Markov model of the natural history of HPV infection incorporating screening and vaccination, was adapted to the French context. A vaccine that would prevent 100 percent of HPV 6, 11, 16, and 18-associated diseases, with lifetime duration and 80 percent coverage, given to girls at age 14 in conjunction with current screening was compared with screening alone. Results were analyzed from both a direct healthcare cost perspective (DCP) and a third-party payer perspective (TPP). Indirect costs such as productivity loss were not taken into account in this analysis.

Results:The incremental cost per life-year gained from vaccination was €12,429 (TPP) and €20,455 (DCP). The incremental cost per quality-adjusted life-year (QALY) for the introduction of HPV vaccination alongside the French cervical cancer screening program was €8,408 (TPP) and €13,809 (DCP). Sensitivity analyses demonstrated that cost-effectiveness was stable, but was most sensitive to the discount rate used for costs and benefits.

Conclusions:Considering the commonly accepted threshold of €50,000 per QALY, these analyses support the fact that adding a quadrivalent HPV vaccine to the current screening program in France is a cost-effective strategy for reducing the burden of cervical cancer, precancerous lesions, and genital warts caused by HPV types 6, 11, 16, and 18.

A cost-effectiveness analysis of adding a human papillomavirus vaccine to the Australian National Cervical Cancer Screening Program

BACKGROUND

The cost-effectiveness of adding a human papillomavirus (HPV) vaccine to the Australian National Cervical Screening Program compared to screening alone was examined.

METHODS

A Markov model of the natural history of HPV infection that incorporates screening and vaccination was developed. A vaccine that prevents 100% of HPV 16/18-associated disease, with a lifetime duration of efficacy and 80% coverage offered through a school program to girls aged 12 years, in conjunction with current screening was compared with screening alone using cost (in Australian dollars) per life-year (LY) saved and quality-adjusted life-year (QALY) saved. Sensitivity analyses included determining the cost-effectiveness of offering a catch-up vaccination program to 14-26-year-olds and accounting for the benefits of herd immunity.

RESULTS

Vaccination with screening compared with screening alone was associated with an incremental cost-effectiveness ratio (ICER) of $51 103 per LY and $18 735 per QALY, assuming a cost per vaccine dose of $115. Results were sensitive to assumptions about the duration of vaccine efficacy, including the need for a booster ($68 158 per LY and $24 988 per QALY) to produce lifetime immunity. Accounting for herd immunity resulted in a more attractive ICER ($36 343 per LY and $13 316 per QALY) for girls only. The cost per LY of vaccinating boys and girls was $92 052 and the cost per QALY was $33 644. The cost per LY of implementing a catch-up vaccination program ranged from $45 652 ($16 727 per QALY) for extending vaccination to 14-year-olds to $78 702 ($34 536 per QALY) for 26-year-olds.

CONCLUSIONS

These results suggest that adding an HPV vaccine to Australia's current screening regimen is a potentially cost-effective way to reduce cervical cancer and the clinical interventions that are currently associated with its prevention via screening alone.

New, and some not-so-new, vaccines for adolescents and diseases they prevent

Adolescents in the United States now have the opportunity to receive new vaccines that prevent invasive meningococcal infections, pertussis (whooping cough), and cervical cancer. Except for their potential to cause serious illness, these infections could not be more different. Their incidence ranges from extremely low to quite high. Early clinical manifestations of infection range from none to life-threatening illness. Two of the vaccines are similar to those already in use, whereas 1 is completely new. In conjunction with the 4 vaccines previously recommended for adolescents (the tetanus and diphtheria booster, hepatitis B, measles-mumps-rubella, and varicella), the 3 new vaccines (meningococcal, human papillomavirus, and the tetanus-diphtheria-pertussis booster [which replaced the tetanus-diphtheria booster]) bring the number recommended for adolescents to 6. In this article, we describe key characteristics of the 3 new vaccines and infections they were designed to prevent. We also briefly discuss other vaccines recommended for all adolescents who have not already received them and new vaccines that are still under development.

Cost-effectiveness of quadrivalent human papillomavirus (HPV) vaccination in Mexico: a transmission dynamic model-based evaluation

We examined the potential health outcomes and cost-effectiveness of quadrivalent human papillomavirus (HPV) 6/11/16/18 vaccination strategies in the Mexican population using a multi-HPV type dynamic transmission model. Assuming similar cervical screening practices, with or without vaccination, we examined the incremental cost-effectiveness of vaccination strategies for 12 year-old females, with or without male vaccination, and temporary age 12-24 catch-up vaccination for females or both sexes. The most effective strategy therein was vaccination of 12-year-olds, plus a temporary 12-24-year-old catch-up program covering both sexes; whereby HPV 6/11/16/18-related cervical cancer, high-grade cervical precancer, and genital wart incidence was reduced by 84-98% during year 50 following vaccine introduction. Incremental cost-effectiveness ratios in the primary analyses ranged from approximately 3000 dollars (U.S.) per quality-adjusted life year (QALY) gained for female vaccination strategies to approximately 16000 dollars /QALY for adding male vaccination with catch-up.

Modeling human papillomavirus and cervical cancer in the United States for analyses of screening and vaccination

BACKGROUND

To provide quantitative insight into current U.S. policy choices for cervical cancer prevention, we developed a model of human papillomavirus (HPV) and cervical cancer, explicitly incorporating uncertainty about the natural history of disease.

METHODS

We developed a stochastic microsimulation of cervical cancer that distinguishes different HPV types by their incidence, clearance, persistence, and progression. Input parameter sets were sampled randomly from uniform distributions, and simulations undertaken with each set. Through systematic reviews and formal data synthesis, we established multiple epidemiologic targets for model calibration, including age-specific prevalence of HPV by type, age-specific prevalence of cervical intraepithelial neoplasia (CIN), HPV type distribution within CIN and cancer, and age-specific cancer incidence. For each set of sampled input parameters, likelihood-based goodness-of-fit (GOF) scores were computed based on comparisons between model-predicted outcomes and calibration targets. Using 50 randomly resampled, good-fitting parameter sets, we assessed the external consistency and face validity of the model, comparing predicted screening outcomes to independent data. To illustrate the advantage of this approach in reflecting parameter uncertainty, we used the 50 sets to project the distribution of health outcomes in U.S. women under different cervical cancer prevention strategies.

RESULTS

Approximately 200 good-fitting parameter sets were identified from 1,000,000 simulated sets. Modeled screening outcomes were externally consistent with results from multiple independent data sources. Based on 50 good-fitting parameter sets, the expected reductions in lifetime risk of cancer with annual or biennial screening were 76% (range across 50 sets: 69-82%) and 69% (60-77%), respectively. The reduction from vaccination alone was 75%, although it ranged from 60% to 88%, reflecting considerable parameter uncertainty about the natural history of type-specific HPV infection. The uncertainty surrounding the model-predicted reduction in cervical cancer incidence narrowed substantially when vaccination was combined with every-5-year screening, with a mean reduction of 89% and range of 83% to 95%.

CONCLUSION

We demonstrate an approach to parameterization, calibration and performance evaluation for a U.S. cervical cancer microsimulation model intended to provide qualitative and quantitative inputs into decisions that must be taken before long-term data on vaccination outcomes become available. This approach allows for a rigorous and comprehensive description of policy-relevant uncertainty about health outcomes under alternative cancer prevention strategies. The model provides a tool that can accommodate new information, and can be modified as needed, to iteratively assess the expected benefits, costs, and cost-effectiveness of different policies in the U.S.

Interleukin-10 gene (IL10) polymorphisms and human papillomavirus clearance among immunosuppressed adolescents

Persistent infection with high-risk human papillomavirus (HPV) is a major risk factor for cervical cancer, and HPV clearance seems to be under host genetic influence. This study evaluated associations between three single nucleotide polymorphisms in the IL10 promoter and clearance of low- or high-risk HPV infection in a cohort of 226 largely HIV-1-infected African-American adolescent females. Among immunosuppressed individuals (HIV-1 seropositive and CD4(+) </= 500), the GCC haplotype in the IL10 promoter was associated with reduced clearance of high-risk HPV16-like [relative hazard (RH), 0.46; 95% confidence interval (95% CI), 0.25-0.85; P = 0.01], HPV18-like (RH, 0.33; 95% CI, 0.16-0.67; P = 0.002), and any high-risk type (RH, 0.37; 95% CI, 0.20-0.68; P = 0.002) but not with low-risk HPV type (RH, 0.60; 95% CI, 0.29-1.25; P = 0.17). No associations were observed among immunocompetent individuals. The IL10 GCC haplotype has been associated with production of relatively high levels of interleukin (IL)-10, which could (a) inhibit cytokines such as IL-2, TNF-alpha, IL-4, IL-6, and IL-12 that are involved in the T(H)1-T(H)2 immunoregulation; (b) down-regulate expression of MHC class I and class II molecules; or (c) induce the transcription of early promoter of HPV, all potentially contributing to duration of HPV infection among immunosuppressed individuals. These results support the hypothesis that IL10 polymorphisms influence the clearance of infection with high-risk HPV types and warrant further studies of host genetic control of HPV pathogenesis and cervical cancer in the context of immunosuppression.

Potential effects of decreased cervical cancer screening participation after HPV vaccination: an example from the U.S

A concern with widespread implementation of HPV vaccination programs is that women may mistakenly decide that they do not need to be screened any longer, and thus be less likely to participate in cervical cancer screening, because they view themselves to be at low-risk of developing cervical cancer. We hypothesized that non-participation in screening among vaccinated young women in the 5 years following vaccination may result in missed CIN 2-3 cases that could progress to cancer. For instance, if 50% fewer women 26-30 years old, who were vaccinated, participate in screening in the United States over a 5 year time horizon, there would be approximately 4 women (per 1000) with missed CIN 2-3. On the other hand, non-participation will reduce the number of false-positive screening test results, as non-participation would avoid approximately 27 false-positive test results, with a decrease in follow-up procedures and costs. These results highlight the importance of educating women to ensure continued screening, as well as the need to consider new approaches to screening in the era of vaccination.

Phase I/II clinical safety studies of terameprocol vaginal ointment

OBJECTIVES

Terameprocol (M4N, EM-1421) is a novel transcription inhibitor that selectively interferes with HPV viral genes E6/E7 with Sp1-dependent promoters, and induces apoptosis by inactivation of the CDC2/cyclin B complex (maturation promoting factor) and production and phosphorylation of survivin. This trial was designed to define the maximum tolerated dose (MTD), dose-limiting toxicity and determine the pharmacokinetic profiles of intravaginal terameprocol in women with HPV-linked cervical squamous intraepithelial neoplasia.

METHODS

An open label, dose escalation Phase I/II clinical trial enrolled women with biopsy confirmed CIN 1, 2 or 3. Terameprocol (45 or 90 mg) was physician-administered directly to the cervix uteri in 3 once weekly applications. The pharmacokinetics after administration were examined on Day 1 of dosing. Patients underwent colposcopic examinations, HPV testing, biomarker assessments, cytology and cervical punch biopsy.

RESULTS

Recruitment ended March 30, 2006 and 7 patients were enrolled. Median age was 24 years. There were no serious adverse events (SAEs) and possible treatment-related Adverse Events (AEs) reported were mild and self-limiting. There was no detectable absorption of terameprocol from the vaginal ointment application.

CONCLUSIONS

Terameprocol in 1% and 2% vaginal ointment use in Phase I/II trials with women with HPV-linked cervical intraepithelial neoplasia has an excellent safety profile, no SAEs reported and mild, self-limiting treatment-related AEs. There was no detectable absorption of terameprocol. These data support the continued evaluation of terameprocol in in vitro and animal efficacy models followed by definitive human Phase II clinical trials in CIN.

Inverse decision theory with applications to screening and diagnosis of cervical intraepithelial neoplasia

OBJECTIVE

Medical decision makers would like to use decision theory to determine optimal treatment strategies for patients, but this requires priors, likelihoods, and losses. It can be very difficult to specify a loss or utility function in a medical setting, especially when considering both patient health outcomes and economic costs. These issues led to the development of Inverse Decision Theory (IDT), which involves determining the set of losses under which a given decision rule is optimal.

METHODS

We apply IDT to the current standard of care for the diagnosis and treatment of precancerous lesions to the cervix, using a Bayesian approach to estimate the probabilities associated with diagnostic tests and make inferences about the region of optimality. There are two ways in which Inverse Decision Theory can be useful: (i) if the decision rule of interest is optimal, then we obtain information about the losses for the optimal treatment strategy, and (ii) if the decision rule of interest is not optimal, then we characterize the losses under which it would be optimal, and assess whether or not it contains reasonable values of the losses.

RESULTS

This paper introduces important clinical results: in particular, we find that the current standard of care for cervical precancer is probably not optimal, and a new decision rule which requires a confirmatory biopsy for all patients with a positive Pap smear test result is better.

CONCLUSION

We have developed a very general and flexible approach for evaluating treatment strategies that could prove useful in a variety of medical applications.

Vaccines against human papillomavirus: perspectives for controlling cervical cancer

Prophylactic vaccines against human papillomavirus (HPV) are on the market and will certainly reduce the incidence of genital warts and the risk of developing cervical cancer. In addition, they will contribute to reducing anal as well as head and neck cancers. However, effort should be made in the short term in order for these vaccines to have a real impact in the developing world, where almost 80% of cervical cancer cases occur. Since the available vaccines include only two of the HPV types found in cancers (approximately 70%), improvements in current mass screening programs - with the use of molecular techniques - must be made, particularly in developing countries. Therapeutic vaccines have been designed to control advanced lesions and residual illness and, although success has usually been obtained in animal models, clinical studies have not yet provided the anticipated results. Finally, the next generations of prophylactic HPV vaccines will probably include subunit vaccines, transgenic bacteria and plants, among others, and could represent useful and cheaper alternatives for reducing cervical cancer, particularly in the developing world.

Virally mediated cervical cancer in the iatrogenically immunocompromised: applications for psychoneuroimmunology

Oncogenic or high-risk (HR) human papillomavirus (HPV) infection is implicated in the pathogenesis of a number of cancers, including cervical cancer. HPV infected individuals who are immunocompromised secondary to acquired (e.g., human immunodeficiency virus [HIV]) or iatrogenic (e.g., systemic lupus erythematosus [SLE] patients and organ and hematopoeitic stem cell transplant recipients undergoing immunosuppressive therapy) immune deficiency are particularly at risk for HPV-initiated cervical neoplasia and cancer. Psychoneuroimmunologic (PNI) research has demonstrated that psychosocial factors such as stress, pessimism, and sleep quality may play a role in the promotion of HPV-mediated cervical neoplasia in HIV-positive women. However, no research to our knowledge has examined PNI mechanisms of HPV-mediated cervical neoplasia and cancer in women who are undergoing iatrogenic immunosuppressive therapy for the treatment of autoimmune disease or the prevention of graft-rejection. This article reviews the PNI mechanisms that may underlie the promotion of HPV-mediated cervical neoplasia and applies this model to HPV-infected women who are iatrogenically immunosuppressed, an understudied population at-risk for cervical cancer. Female transplant recipients, one such group, may provide a unique paradigm in which to explore further PNI mechanisms of HPV-mediated cervical neoplasia.

The Natural History of Human Papillomavirus Infection and Cervical Intraepithelial Neoplasia Among Young Women in the Guanacaste Cohort Shortly After Initiation of Sexual Life

OBJECTIVE

Cross-sectional analyses of our 10,000-woman, population-based Guanacaste cohort suggest a lag of > or =10 years between the peak of human papillomavirus (HPV) infection and the later peak of cervical intraepithelial neoplasia grade 3 (CIN 3). We wanted to explore early HPV natural history and CIN 3 prospectively.

STUDY DESIGN

As part of the Guanacaste cohort, we followed 206 initially virginal women aged 18 to 26 semiannually for a median of 3.6 years after initiation of sexual life.

RESULTS

A total of 53.4% of women tested positive during the study for > or =1 HPV type. Very few infections persisted for >1 to 2 years. Three women had histologically confirmed CIN 3, of which 2 showed persistent HPV 16. The other had serologic evidence of HPV 31.

CONCLUSIONS

HPV infection occurs frequently and clears rapidly in most young women initiating sexual intercourse. Persistent HPV 16 can cause early CIN 3. The peak age for CIN 3 will decline with the increased screening intensity and sensitivity typical of longitudinal studies.

Correlates of intent to be vaccinated against human papillomavirus: an exploratory study of college-aged women

This study identified correlates of human papillomavirus (HPV) vaccine acceptance among college-aged women. Data were collected by self-administered questionnaire. In multivariate analyses, women having vaginal sex (past 12 months) were nearly four times more likely to indicate acceptance (P = 0.0001). Those reporting ever having a sexually transmissible infection (STI; P = 0.03) and those indicating ever having an abnormal Pap test (P = 0.03) were more likely to indicate acceptance. Thus, three forms of 'exposure' (having sex, having an STI or abnormal Pap) may be linked to vaccine acceptance among young women attending universities. The findings suggest that opportunities may exist for clinic-based HPV vaccine promotion among this population of women.

Cost-effectiveness analyses of human papillomavirus vaccination

With a human papillomavirus (HPV) vaccine soon to become available for widespread use, several studies have modelled the cost-effectiveness of vaccination. These pioneer studies are likely to be influential on the design of further analyses, and we have therefore summarised and critically reviewed the strengths and limitations of their methods and assumptions. Despite a lack of transparency in some key elements, the most influential assumptions were identified as relating to vaccine effectiveness, cervical screening, and model design. Although the studies suggest that the introduction of an HPV vaccine could be cost effective compared with current practice in the USA, there is still substantial uncertainty around key variables, and model validation seems insufficient. The desirability of vaccinating boys in addition to girls has been explored in only one study. Further refinements to model design and epidemiological variables of (type-specific) HPV disease progression, and expansions on the options for vaccine use, are required for policy making.

Review of the economic and quality-of-life burden of cervical human papillomavirus disease

OBJECTIVE

The purpose of this study was to conduct a systematic literature review on the economic burden and health-related quality-of-life impact of cervical human papillomavirus disease.

STUDY DESIGN

A systematic review of cost-of-illness studies and health-related quality-of-life studies was conducted. PubMed, Embase, and PsycINFO databases were searched with the use of predefined terms.

RESULTS

Nine economic and 24 quality-of-life studies were identified. The annual health care costs of human papillomavirus-related conditions in the United States range from 2.25-4.6 billion dollars (2005 US dollars). The burden of human papillomavirus is second only to human immunodeficiency virus among sexually transmitted diseases. Health-related quality-of-life areas that are impacted substantially by human papillomavirus include emotional, social, and sexual functioning.

CONCLUSION

The economic and quality-of-life burden of cervical human papillomavirus disease is significant and highlights the need for treatment and prevention options for this condition.

Rates and probabilities in economic modelling: transformation, translation and appropriate application

Economic modelling is increasingly being used to evaluate the cost effectiveness of health technologies. One of the requirements for good practice in modelling is appropriate application of rates and probabilities. In spite of previous descriptions of appropriate use of rates and probabilities, confusions persist beyond a simple understanding of their definitions. The objective of this article is to provide a concise guide to understanding the issues surrounding the use of rates and probabilities reported in the literature in economic models, and an understanding of when and how to transform them appropriately. The article begins by defining rates and probabilities and shows the essential difference between the two measures. Appropriate conversions between rates and probabilities are discussed, and simple examples are provided to illustrate the techniques and pitfalls. How the transformed rates and probabilities may be used in economic models is then described and some recommendations are suggested.

Primary screening for cervical cancer through self sampling

OBJECTIVE

To evaluate the use of community health agents (CHAs) to instruct women living in poor rural areas in obtaining self-collected cervical samples and compare the high-risk HPV (hrHPV) hybrid capture (HC) results obtained to those for gynecologist-collected samples.

METHODS

After a one-day training, CHAs visited sexually active women, instructing each in the use of collection brush and the Universal Collection Medium tube. One week thereafter, a gynecologist collected cervical samples from, and performed colposcopies on, the same women. A single reference lab performed all HCs.

RESULTS

878 women (Age: 15-69 years) participated. Among self-collected samples, hrHPV prevalence was 33.9% (95% CI: 30.8%-37%), compared with 28.6% (95% CI: 27%-30%) among gynecologist-collected samples. However, 9.3% of the patients were HPV HC II-positive in the self-collected sample and HPV HC II-negative in the gynecologist-collected samples (95% CI: 7.38%-11.22%), whereas 4% tested positive in gynecologist-collected samples and negative in self-collected samples (95% CI: 2.7%-5.3%) (P<0.01; kappa=0.7). Of 9 cases of histologically-confirmed, high-grade squamous intraepithelial lesion, self-collected and provider-collected samples missed one each.

CONCLUSION

Self-collected vaginal sampling could be made an additional CHA function under existing program conditions, improving access to cervical cancer screening in poor rural settings.

Chapter 28: Studies to assess the long-term efficacy and effectiveness of HPV vaccination in developed and developing countries

We review studies of the implementation of human papillomavirus (HPV) vaccination programmes in developed and developing countries. The review spans the period from establishment of long-term vaccine efficacy follow-up studies, operational research on issues of vaccine preparedness, and relevant predictive modelling studies during the pre-licensure phase to plans of phase IV effectiveness trials, forms of epidemiological surveillance, and further operational research in the post-licensure phase. Much of the research is already ongoing. Depending on the results of the planned immuno bridging studies among HIV-negative and HIV-positive women, further phase III and/or phase IV trials may be warranted.

Trends in the incidence of invasive and in situ vulvar carcinoma

OBJECTIVE

To characterize the incidence of vulvar carcinoma in situ and vulvar cancer over time.

METHODS

We used the Surveillance Epidemiology and End Results database to assess trends in the incidence of vulvar cancer over a 28-year period (1973 through 2000) and determined whether there had been a change in incidence over time. Information collected included patient characteristics, primary tumor site, tumor grade, and follow-up for vital status. We calculated the incidence rates by decade of age, used chi(2) tests to compare demographic characteristics, and tested for trends in incidence over time.

RESULTS

A total of 13,176 in situ and invasive vulvar carcinomas were identified; 57% of the women were diagnosed with in situ, 44% with invasive disease. Vulvar carcinoma in situ increased 411% from 1973 to 2000. Invasive vulvar cancer increased 20% during the same period. The incidence rates for in situ and invasive vulvar carcinomas are distributed differently across the age groups. In situ carcinoma incidence increases until the age of 40-49 years and then decreases, whereas invasive vulvar cancer risk increases as a woman ages, increasing more quickly after 50 years of age.

CONCLUSION

The incidence of in situ vulvar carcinoma is increasing. The incidence of invasive vulvar cancer is also increasing but at a much lower rate.

Mathematical model of HPV provides insight into impacts of risk factors and vaccine

Kim discusses a study by Barnabas and colleagues in PLoS Medicine in which the researchers used a mathematical model to assess the effect of sexual transmission of HPV 16 in a Finnish population.

Epidemiology of HPV 16 and cervical cancer in Finland and the potential impact of vaccination: mathematical modelling analyses

BACKGROUND

Candidate human papillomavirus (HPV) vaccines have demonstrated almost 90%-100% efficacy in preventing persistent, type-specific HPV infection over 18 mo in clinical trials. If these vaccines go on to demonstrate prevention of precancerous lesions in phase III clinical trials, they will be licensed for public use in the near future. How these vaccines will be used in countries with national cervical cancer screening programmes is an important question.

METHODS AND FINDINGS

We developed a transmission model of HPV 16 infection and progression to cervical cancer and calibrated it to Finnish HPV 16 seroprevalence over time. The model was used to estimate the transmission probability of the virus, to look at the effect of changes in patterns of sexual behaviour and smoking on age-specific trends in cancer incidence, and to explore the impact of HPV 16 vaccination. We estimated a high per-partnership transmission probability of HPV 16, of 0.6. The modelling analyses showed that changes in sexual behaviour and smoking accounted, in part, for the increase seen in cervical cancer incidence in 35- to 39-y-old women from 1990 to 1999. At both low (10% in opportunistic immunisation) and high (90% in a national immunisation programme) coverage of the adolescent population, vaccinating women and men had little benefit over vaccinating women alone. We estimate that vaccinating 90% of young women before sexual debut has the potential to decrease HPV type-specific (e.g., type 16) cervical cancer incidence by 91%. If older women are more likely to have persistent infections and progress to cancer, then vaccination with a duration of protection of less than 15 y could result in an older susceptible cohort and no decrease in cancer incidence. While vaccination has the potential to significantly reduce type-specific cancer incidence, its combination with screening further improves cancer prevention.

CONCLUSIONS

HPV vaccination has the potential to significantly decrease HPV type-specific cervical cancer incidence. High vaccine coverage of women alone, sustained over many decades, with a long duration of vaccine-conferred protection, would have the greatest impact on type-specific cancer incidence. This level of coverage could be achieved through national coordinated programmes, with surveillance to detect cancers caused by nonvaccine oncogenic HPV types.

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.

Labial edema following treatment of condyloma acuminata with CO(2) laser in an adolescent: a case report and literature review

PURPOSE

To describe a case of bilateral labial edema in an adolescent patient and review the literature on this rare occurrence.

MATERIAL

A 16-year-old girl was treated for widespread genital condyloma acuminata with CO(2) laser under general anesthesia and local lidocaine injections. Severe bilateral labial edema occurred after 48 hours.

RESULTS

Lidocaine and Latex dermal patch tests for delayed hypersensitivity were negative. The edema resolved following treatment with local ice packs and magnesium sulfate compresses for 2 weeks.

CONCLUSION

This is the first description of severe bilateral labial edema after CO(2) laser treatment for condyloma acuminata. We suggest that transient local lymphatic obstruction was the reason for this complication. The literature on this rare occurrence is reviewed.

Modeling the sexual transmissibility of human papillomavirus infection using stochastic computer simulation and empirical data from a cohort study of young women in Montreal, Canada

The authors estimated plausible ranges of the probability of human papillomavirus (HPV) transmission per coital act among newly forming couples by using stochastic computer simulation. Comparative empirical data were obtained in 1996-2001 from a cohort study of female university students in Montreal, Canada. Female prevalence and frequency of sexual intercourse and condom use were set equal to those in the cohort. Simulations included 240 combinations of male prevalence, the relative risk for protected versus unprotected sex, and per-act transmission probabilities. Those that produced expected HPV incidence within the 95% confidence interval observed in the cohort were selected. The observed 6-month cumulative incidence following acquisition of a new partner was 17.0% (95% confidence interval: 11.4, 23.0). Expected incidences consistent with those from cohort findings occurred in 54/240 simulations. The range of per-act transmission probabilities was 5-100% (median, 40%). Male HPV prevalence was the same as or greater than that for women in all consistent simulations. Varying condom effectiveness did not produce better-fitting data. This simulation suggests that HPV transmissibility is several-fold higher than that for other viral sexually transmitted infections such as human immunodeficiency virus or herpes simplex virus 2. With high transmissibility, any potential protective effect of condoms would disappear over multiple intercourse acts, underlining the need for an effective HPV vaccine.

The German Cervical Cancer Screening Model: development and validation of a decision-analytic model for cervical cancer screening in Germany

BACKGROUND

We sought to develop and validate a decision-analytic model for the natural history of cervical cancer for the German health care context and to apply it to cervical cancer screening.

METHODS

We developed a Markov model for the natural history of cervical cancer and cervical cancer screening in the German health care context. The model reflects current German practice standards for screening, diagnostic follow-up and treatment regarding cervical cancer and its precursors. Data for disease progression and cervical cancer survival were obtained from the literature and German cancer registries. Accuracy of Papanicolaou (Pap) testing was based on meta-analyses. We performed internal and external model validation using observed epidemiological data for unscreened women from different German cancer registries. The model predicts life expectancy, incidence of detected cervical cancer cases, lifetime cervical cancer risks and mortality.

RESULTS

The model predicted a lifetime cervical cancer risk of 3.0% and a lifetime cervical cancer mortality of 1.0%, with a peak cancer incidence of 84/100,000 at age 51 years. These results were similar to observed data from German cancer registries, German literature data and results from other international models. Based on our model, annual Pap screening could prevent 98.7% of diagnosed cancer cases and 99.6% of deaths due to cervical cancer in women completely adherent to screening and compliant to treatment. Extending the screening interval from 1 year to 2, 3 or 5 years resulted in reduced screening effectiveness.

CONCLUSIONS

This model provides a tool for evaluating the long-term effectiveness of different cervical cancer screening tests and strategies.

Cost-effectiveness of Extending Cervical Cancer Screening Intervals Among Women With Prior Normal Pap Tests

OBJECTIVE

Annual cervical cancer screening in women with many prior normal Pap tests is common despite limited evidence on the cost-effectiveness of this strategy. We estimated the cost-effectiveness of screening women with 3 or more prior normal tests compared with screening those with no prior tests.

METHODS

We used a validated cost-effectiveness model in conjunction with data on the prevalence of biopsy-proven cervical neoplasia in women enrolled in the Centers for Disease Control and Prevention National Breast and Cervical Cancer Early Detection Program. Women were grouped according to age at the final Program Pap test (aged < 30, 30-44, 45-59, and 60-65 years) and by screening history (0, 1, 2, and 3+ consecutive prior normal Program tests) to estimate cost per life-year and quality-adjusted life-year associated with annual, biennial, and triennial screening.

RESULTS

For women aged 30-44 years with no prior tests, incremental cost-effectiveness ratios ranged from 20,533 US dollars for screening triennially (compared with no further screening) to 331,837 US dollars for screening annually (compared with biennially) per life-year saved. Among same-aged women with 3 or more prior normal Program tests, incremental cost-effectiveness ratios for the same measures ranged from 60,029 US dollars to 709,067 US dollars per life-year saved. Inclusion of the most conservative utility estimates resulted in incremental cost-effectiveness ratios in excess of 100,000 US dollars per quality-adjusted life-year saved associated with annual screening of same-aged women with 3 or more prior normal tests compared with biennial screening.

CONCLUSION

As the number of prior normal Pap tests increases, the costs per life-year saved increase substantially. Resources should be prioritized for screening those never or rarely screened women.

LEVEL OF EVIDENCE

II-2.