Using the Cancer Risk Management Model to evaluate the health and economic impacts of cytology compared with human papillomavirus DNA testing for primary cervical cancer screening in Canada

Priorities among effective clinical preventive services in British Columbia, Canada

BACKGROUND

Despite the long-standing experience of rating the evidence for clinical preventive services, the delivery of effective clinical preventive services in Canada and elsewhere is less than optimal. We outline an approach used in British Columbia to assist in determining which effective clinical preventive services are worth doing.

METHODS

We calculated the clinically preventable burden and cost-effectiveness for 28 clinical preventive services that received a 'strong or conditional (weak) recommendation for' by the Canadian Task Force on Preventive Health Care or an 'A' or 'B' rating by the United States Preventive Services Task Force. Clinically preventable burden is the total quality adjusted life years that could be gained if the clinical preventive services were delivered at recommended intervals to a British Columbia birth cohort of 40,000 individuals over the years of life that the service is recommended. Cost-effectiveness is the net cost per quality adjusted life year gained.

RESULTS

Clinical preventive services with the highest population impact and best value for money include services that address tobacco use in adolescents and adults, exclusive breastfeeding, and screening for hypertension and other cardiovascular disease risk factors followed by appropriate pharmaceutical treatment. In addition, alcohol misuse screening and brief counseling, one-time screening for hepatitis C virus infection in British Columbia adults born between 1945 and 1965, and screening for type 2 diabetes approach these high-value clinical preventive services.

CONCLUSIONS

These results enable policy makers to say with some confidence what preventive manoeuvres are worth doing but further work is required to determine the best way to deliver these services to all those eligible and to establish what supportive services are required. After all, if a clinical preventive service is worth doing, it is worth doing well.

The OncoSim-Breast Cancer Microsimulation Model

Background: OncoSim-Breast is a Canadian breast cancer simulation model to evaluate breast cancer interventions. This paper aims to describe the OncoSim-Breast model and how well it reproduces observed breast cancer trends. Methods: The OncoSim-Breast model simulates the onset, growth, and spread of invasive and ductal carcinoma in situ tumours. It combines Canadian cancer incidence, mortality, screening program, and cost data to project population-level outcomes. Users can change the model input to answer specific questions. Here, we compared its projections with observed data. First, we compared the model’s projected breast cancer trends with the observed data in the Canadian Cancer Registry and from Vital Statistics. Next, we replicated a screening trial to compare the model’s projections with the trial’s observed screening effects. Results: OncoSim-Breast’s projected incidence, mortality, and stage distribution of breast cancer were close to the observed data in the Canadian Cancer Registry and from Vital Statistics. OncoSim-Breast also reproduced the breast cancer screening effects observed in the UK Age trial. Conclusions: OncoSim-Breast’s ability to reproduce the observed population-level breast cancer trends and the screening effects in a randomized trial increases the confidence of using its results to inform policy decisions related to early detection of breast cancer.

Estimates of future cancer mortality attributable to modifiable risk factors in Canada

OBJECTIVES

Modifiable lifestyle, environmental, and infectious risk factors associated with cancer impact both cancer incidence and mortality at the population level. Most studies estimating this burden focus on cancer incidence. However, because these risk factors are associated with cancers of disparate mortality rates, the burden associated with cancer incidence could differ from cancer mortality. Therefore, estimating the cancer mortality attributable to these risk factors provides additional insight into cancer prevention. Here, we estimated future cancer deaths and the number of avoidable deaths in Canada due to modifiable risk factors.

METHODS

The projected cancer mortality data came from OncoSim, a web-based microsimulation tool. These data were applied to the methodological framework that we previously used to estimate the population attributable risks and the potential impact fractions of modifiable risk factors on Canadian cancer incidence.

RESULTS

We estimated that most cancer deaths will be attributed to tobacco smoking with an average of 27,900 deaths annually from 2024 to 2047. If Canada's current trends in excess body weight continue, cancer deaths attributable to excess body weight would double from 2786 deaths in 2024 to 5604 deaths in 2047, becoming the second leading modifiable cause of cancer death. Applying targets to reduce these risk factors, up to 34,600 cancer deaths could be prevented from 2024 to 2047.

CONCLUSION

Our simulated results complement our previous findings on the cancer incidence burden since decreasing the overall burden of cancer will be accelerated through a combination of decreasing cancer incidence and improving survival outcomes through improved treatments.

Modeling the Balance of Benefits and Harms of Cervical Cancer Screening with Cytology and Human Papillomavirus Testing

BACKGROUND

Benefits of screening should outweigh its potential harms. We compared various metrics to assess the balance of benefits and harms of cervical cancer screening.

METHODS

We used a cervical cancer natural history Markov model calibrated to the Canadian context to simulate 100,000 unvaccinated women over a lifetime of screening with either cytology every 3 years or human papillomavirus (HPV) testing every 5 years. We estimated the balance of benefits and harms attributable to screening using various metrics, including colposcopies/life-year gained, and net lifetime quality-adjusted life-years (QALY) gained, a measure integrating women's health preferences. We present the average (minimum-maximum) model predictions.

RESULTS

Cytology-based screening led to 1,319,854 screening tests, 30,395 colposcopies, 13,504 life-years gained over a lifetime, 98 screening tests/life-year gained, 2.3 (1.6-3.3) colposcopies/life-year gained, and a net lifetime gain of 10,735 QALY (5,040-17,797). HPV-based screening with cytology triage in the same population would lead to 698,250 screening tests, 73,296 colposcopies, 15,066 life-years gained over a lifetime, 46 screening tests/life-year gained, 4.9 colposcopies/life-year gained (2.9-11.1), and a net lifetime gain of 11,690 QALY (4,409-18,742). HPV-based screening was predicted to prevent more cancers, but also incur more screening harms than cytology-based screening.

CONCLUSIONS

Metrics using colposcopies as the main harm outcome favored cytology-based screening, whereas metrics based on screening tests and health preferences tended to favor HPV-based screening strategies.

IMPACT

Whether HPV-based screening will improve the balance between benefits and harms of cervical cancer screening depends on how the balance between benefits and harms is assessed.

The OncoSim model: development and use for better decision-making in Canadian cancer control

The Canadian Partnership Against Cancer was created in 2007 by the federal government to accelerate cancer control across Canada. Its OncoSim microsimulation model platform, which consists of a suite of specific cancer models, was conceived as a tool to augment conventional resources for population-level policy- and decision-making. The Canadian Partnership Against Cancer manages the OncoSim program, with funding from Health Canada and model development by Statistics Canada. Microsimulation modelling allows for the detailed capture of population heterogeneity and health and demographic history over time. Extensive data from multiple Canadian sources were used as inputs or to validate the model. OncoSim has been validated through expert consultation; assessments of face validity, internal validity, and external validity; and model fit against observed data. The platform comprises three in-depth cancer models (lung, colorectal, cervical), with another in-depth model (breast) and a generalized model (25 cancers) being in development. Unique among models of its class, OncoSim is available online for public sector use free of charge. Users can customize input values and output display, and extensive user support is provided. OncoSim has been used to support decision-making at the national and jurisdictional levels. Although simulation studies are generally not included in hierarchies of evidence, they are integral to informing cancer control policy when clinical studies are not feasible. OncoSim can evaluate complex intervention scenarios for multiple cancers. Canadian decision-makers thus have a powerful tool to assess the costs, benefits, cost-effectiveness, and budgetary effects of cancer control interventions when faced with difficult choices for improvements in population health and resource allocation.

Introduction of molecular HPV testing as the primary technology in cervical cancer screening: Acting on evidence to change the current paradigm

Since being introduced in the 1940s, cervical cytology - despite its limitations - has had unequivocal success in reducing cervical cancer burden in many countries. However, we now know that infection with human papillomavirus (HPV) is a necessary cause of cervical cancer and there is overwhelming evidence from large-scale clinical trials, feasibility studies and real-world experience that supports the introduction of molecular testing for HPV as the primary technology in cervical cancer screening (i.e., "HPV primary screening"). While questions remain about the most appropriate age groups for screening, screening interval and triage approach, these should not be considered barriers to implementation. Many countries are in various stages of adopting HPV primary screening, whereas others have not taken any major steps towards introduction of this approach. As a group of clinical experts and researchers in cervical cancer prevention from across Canada, we have jointly authored this comprehensive examination of the evidence to implement HPV primary screening. Our intention is to create a common understanding among policy makers, agencies, clinicians, researchers and other stakeholders about the evidence concerning HPV primary screening to catalyze the adoption of this improved approach to cervical cancer prevention. With the first cohort of vaccinated girls now turning 21, the age when routine screening typically begins, there is increased urgency to introduce HPV primary screening, whose performance may be less adversely affected compared with cervical cytology as a consequence of reduced lesion prevalence post-vaccination.

Validation of Novaprep(®) HQ+ liquid-based cytology medium for high-risk human papillomavirus detection by hc2

Background

Preanalytical conditions determine the reliability and validity of bioassays. Therefore, the analytic performances of biological tests need to be determined when preanalytical steps differ from those recommended by the manufacturer. The objective of the study was to assess the analytic performance of the hc2 test for the detection of high-risk HPV DNA from cells stored in the new Novaprep® HQ+ medium.

Methods

Repeatability, reproducibility, method comparison and stability (-20 °C, +4 °C, +20 °C and +40 °C up to six months) were evaluated from HPV16 and HPV18 positive cell lines diluted in the Novaprep® HQ+ medium and the reference Specimen Transport Medium (STM). A series of cervical samples with atypical squamous cells of undetermined significance (ASC-US) cytology and stored in the Novaprep® HQ+ medium was also tested.

Results

Coefficients of variation for repeatability and reproducibility were less than 8 %. Method comparison showed perfect agreement in hc2 results when the HPV-positive cells were diluted in HQ+ and reference media. Stability experiments demonstrated that the storage conditions did not alter the hc2 test results. Furthermore, clinical samples were adequately preserved for hc2 testing.

Conclusions

Overall, our data show that the new Novaprep HQ+ medium is suitable for high-risk HPV testing by hc2.