Predicting cohort-specific cervical cancer incidence from population-based HPV prevalence surveys: a worldwide study (original) (raw)
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Using HPV prevalence to predict cervical cancer incidence
International Journal of Cancer, 2013
Knowledge of a country's cervical cancer (CC) burden is critical to informing decisions about resource allocation to combat the disease; however, many countries lack cancer registries to provide such data. We developed a prognostic model to estimate CC incidence rates in countries without cancer registries, leveraging information on human papilloma virus (HPV) prevalence, screening, and other country-level factors. We used multivariate linear regression models to identify predictors of CC incidence in 40 countries. We extracted age-specific HPV prevalence (10-year age groups) by country from a meta-analysis in women with normal cytology (N 5 40) and matched to most recent CC incidence rates from Cancer Incidence in Five Continents when available (N 5 36), or Globocan 2008 (N 5 4). We evaluated country-level behavioral, economic, and public health indicators. CC incidence was significantly associated with age-specific HPV prevalence in women aged 35-64 (adjusted R-squared 0.41) (''base model''). Adding geographic region to the base model increased the adjusted R-squared to 0.77, but the further addition of screening was not statistically significant. Similarly, country-level macro-indicators did not improve predictive validity. Age-specific HPV prevalence at older ages was found to be a better predictor of CC incidence than prevalence in women under 35. However, HPV prevalence could not explain the entire CC burden as many factors modify women's risk of progression to cancer. Geographic region seemed to serve as a proxy for these country-level indicators. Our analysis supports the assertion that conducting a population-based HPV survey targeting women over age 35 can be valuable in approximating the CC risk in a given country.
Population Health Metrics, 2007
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 typespecific HPV infection. The uncertainty surrounding the model-predicted reduction in cervical
American Journal of Epidemiology, 2003
The authors studied the time-dependent association between human papillomavirus (HPV) infection and squamous intraepithelial lesions (SIL) among women enrolled in a cohort study in Brazil (1993Brazil ( -2002, using repeated Papanicolaou cytologic examination and HPV testing by polymerase chain reaction. Through simulation with conceivable alternative cohort designs, they investigated different regression modeling approaches using time-varying covariates, time-varying hazard ratio functions, and repeated events to assess the effect of delay in lesion detection. Associations between HPV and early SIL were of high magnitude. The age-adjusted hazard ratios for the association between HPV at enrollment and low-grade SIL decreased gradually with time until 72 months for both oncogenic types of HPV (hazard ratio = 3.96, 95% confidence interval (CI): 2.5, 6.4) and nononcogenic types (hazard ratio = 2.37, 95% CI: 1.3, 4.3). The hazard ratio for incident high-grade SIL remained constant, ranging from 7.15 (95% CI: 2.0, 25.1) at 12 months to 6.26 (95% CI: 2.7, 14.5) at 72 months for oncogenic types of HPV. With oncogenic HPV as the time-dependent predictor variable, the hazard ratios for incident SIL and high-grade SIL events were 14.2 (95% CI: 8.7, 23.1) and 32.7 (95% CI: 8.4, 127.3), respectively. Investigators may underestimate the prognostic value of HPV detection using designs that rely on HPV ascertainment at a single time point. The waning in hazard ratios should be considered in the implementation of HPV testing-based screening programs. cervix neoplasms; longitudinal studies; papillomavirus, human; precancerous conditions; statistics; survival analysis Abbreviations: CI, confidence interval; HPV, human papillomavirus; SIL, squamous intraepithelial lesion.
Modeling Cervical Cancer Prevention in Developed Countries
Vaccine, 2008
Cytology-based screening has reduced cervical cancer mortality in countries able to implement, sustain and financially support organized programs that achieve broad coverage. These ongoing secondary prevention efforts considerably complicate the question of whether vaccination against Human Papillomavirus (HPV) types-16 and 18 should be introduced. Policy questions focus primarily on the target ages of vaccination, appropriate ages for a temporary "catch-up" program, possible revisions in screening policies to optimize synergies with vaccination, including the increased used of HPV DNA testing, and the inclusion of boys in the vaccination program. Decisionanalytic models are increasingly being developed to simulate disease burden and interventions in different settings in order to evaluate the benefits and cost-effectiveness of primary and secondary interventions for informed decision-making. This article is a focused review on existing mathematical models that have been used to evaluate HPV vaccination in the context of developed countries with existing screening programs. Despite variations in model assumptions and uncertainty in existing data, pre-adolescent vaccination of girls is consistently found to be attractive in the context of current screening practices, provided there is complete and lifelong vaccine protection and widespread vaccination coverage. Questions related to catch-up vaccination programs, potential benefits of other non-cervical cancer outcomes and inclusion of boys are subject to far more uncertainty, and results from these analyses have reached conflicting conclusions. Most analyses find that some catch-up vaccination is warranted but becomes increasingly unattractive as the catch-up age is extended, and vaccination of boys is unlikely to be cost-effective if reasonable levels of coverage are achieved in girls or coverage among girls can be improved. The objective of the review is to highlight points of consensus and qualitative themes, to discuss the areas of divergent findings, and to provide insight into critical decisions related to cervical cancer prevention.
The Lancet, 2020
Background The WHO Director-General has issued a call for action to eliminate cervical cancer as a public health problem. To help inform global efforts, we modelled potential human papillomavirus (HPV) vaccination and cervical screening scenarios in low-income and lower-middle-income countries (LMICs) to examine the feasibility and timing of elimination at different thresholds, and to estimate the number of cervical cancer cases averted on the path to elimination. Methods The WHO Cervical Cancer Elimination Modelling Consortium (CCEMC), which consists of three independent transmission-dynamic models identified by WHO according to predefined criteria, projected reductions in cervical cancer incidence over time in 78 LMICs for three standardised base-case scenarios: girls-only vaccination; girls-only vaccination and once-lifetime screening; and girls-only vaccination and twice-lifetime screening. Girls were vaccinated at age 9 years (with a catch-up to age 14 years), assuming 90% coverage and 100% lifetime protection against HPV types 16, 18, 31, 33, 45, 52, and 58. Cervical screening involved HPV testing once or twice per lifetime at ages 35 years and 45 years, with uptake increasing from 45% (2023) to 90% (2045 onwards). The elimination thresholds examined were an average age-standardised cervical cancer incidence of four or fewer cases per 100 000 women-years and ten or fewer cases per 100 000 women-years, and an 85% or greater reduction in incidence. Sensitivity analyses were done, varying vaccination and screening strategies and assumptions. We summarised results using the median (range) of model predictions. Findings Girls-only HPV vaccination was predicted to reduce the median age-standardised cervical cancer incidence in LMICs from 19•8 (range 19•4-19•8) to 2•1 (2•0-2•6) cases per 100 000 women-years over the next century (89•4% [86•2-90•1] reduction), and to avert 61•0 million (60•5-63•0) cases during this period. Adding twice-lifetime screening reduced the incidence to 0•7 (0•6-1•6) cases per 100 000 women-years (96•7% [91•3-96•7] reduction) and averted an extra 12•1 million (9•5-13•7) cases. Girls-only vaccination was predicted to result in elimination in 60% (58-65) of LMICs based on the threshold of four or fewer cases per 100 000 women-years, in 99% (89-100) of LMICs based on the threshold of ten or fewer cases per 100 000 women-years, and in 87% (37-99) of LMICs based on the 85% or greater reduction threshold. When adding twice-lifetime screening, 100% (71-100) of LMICs reached elimination for all three thresholds. In regions in which all countries can achieve cervical cancer elimination with girls-only vaccination, elimination could occur between 2059 and 2102, depending on the threshold and region. Introducing twice-lifetime screening accelerated elimination by 11-31 years. Long-term vaccine protection was required for elimination. Interpretation Predictions were consistent across our three models and suggest that high HPV vaccination coverage of girls can lead to cervical cancer elimination in most LMICs by the end of the century. Screening with high uptake will expedite reductions and will be necessary to eliminate cervical cancer in countries with the highest burden.
Research Square (Research Square), 2023
Human papillomavirus (HPV) is the cause of almost all cases of cervical cancer, a disease that kills some 340,000 women per year. The timeline from initial infection with HPV to the onset of invasive cervical cancer spans decades, and observational studies of this process are limited to settings in which treatment of precancerous lesions was withheld or inadequate. Such studies have been critical for understanding the natural history of HPV, but some uncertainty remains as to how generalizable this process is across geographical settings, especially given variation in the prevalence of factors known to affect the host-side immune response to HPV, such as HIV and tobacco use. In this study, we create models for the 30 most populous countries in Sub-Saharan Africa, each with country-speci c demographic, and behavioral inputs. We found that it was not possible to t the data if we assumed that the natural history parameters were the same for all countries, even after accounting for demographic and behavioral differences, but that we could achieve a good t with the addition of a single immunocompetence parameter for each country. Our results indicate that variation in host immune responses may play a role in explaining the differences in the burden of cervical cancer between countries, which in turn implies a greater need for more geographically diverse data collection to understand the natural history of HPV.
American Journal of Epidemiology, 2020
The elimination of cervical cancer rests on high efficacy of human papillomavirus (HPV) vaccines. The HPV type distribution among cases of invasive cervical cancer (ICC) is used to make predictions about the impact of eliminating different types of HPV, but accumulating evidence of differences in age-specific cancer incidence by HPV type exists. We used one of the largest population-based series of HPV genotyping of ICCs (n = 2,850; Sweden, 2002–2011) to estimate age-specific ICC incidence by HPV type and obtain estimates of the cancer-protective impact of the removal of different HPV types. In the base case, the age-specific ICC incidence had 2 peaks, and the standardized lifetime risk (SLTR, the lifetime number of cases per birth cohort of 100,000 females) for HPV-positive ICC was 651 per 100,000 female births. In the absence of vaccine types HPV 16 and HPV 18, the SLTR for ICC was reduced to 157 per 100,000 female births (24% of HPV-positive SLTR). Elimination of all 9 types that...
International Journal of Cancer, 2011
Mounting evidence supports incorporation of HPV testing into cervical screening; however, the optimal test format and target population have yet to be confirmed. Assessment of the potential benefits of type-specific testing requires estimation of the risk associated with infection with individual HPV types. However, the risk posed by individual HPV types may be population specific and influenced by cervical screening practice. The existing data on HPV type-specific risk is derived largely from unscreened populations. Our study addressed the lack of data on HPV type-specific risk in cytologically screened populations using a casecontrol study of 262 invasive cervical cancers diagnosed in Wales between 2000 and 2006, and 8,428 controls who attended for cytological screening in 2004. The analysis showed that the odds ratios (ORs) for infection with HPV 16 and 18 are considerable; 2770 (95% CI 1050-7320) and 950 (95% CI 330-2740), respectively, and that the OR for other oncogenic types are in general considerably less (ranging, where quantified, from 20.2 to 386 in the same population). The effect of age on OR associated with particular HPV types was also assessed; this indicated that infection with a high-risk HPV in women older than 40 years was associated with an approximately 30-fold increased risk of invasive cervical cancer relative to women younger than 40 years. These results indicate that there is significant prognostic information associated with knowledge of HPV type.