Benefit of cervical screening at different ages: evidence from the UK audit of screening histories.
ABSTRACT: While most experts agree that cervical screening is effective, there remains controversy over the most appropriate screening interval. Annual screening is common in North America. In England, some argue for 3-yearly screening while others believe 5-yearly screening is adequate, and the frequency varies from one part of the country to another. Screening histories of 1305 women aged 20-69 years, diagnosed with frankly invasive cervical cancer and 2532 age-matched controls were obtained from UK screening programme databases. Data were analysed in terms of time since last negative, and time since last screening smear. Five-yearly screening offers considerable protection (83%) against cancer at ages 55-69 years and even annual screening offers only modest additional protection (87%). Three-yearly screening offers additional protection (84%) over 5-yearly screening (73%) for cancers at ages 40-54 years, but is almost as good as annual screening (88%). In women aged 20-39 years, even annual screening is not as effective (76%) as 3-yearly screening in older women, and 3 years after screening cancer rates return to those in unscreened women. This calls into question the policy of having a uniform screening interval from age 20 to 64 years and stresses the value of screening in middle-aged women. British Journal of Cancer (2003) 89, 88-93. doi:10.1038/sj.bjc.6600974 www.bjcancer.com
Project description:The aim of this study is to evaluate different options for introducing liquid-based cytology (LBC) and human papillomavirus (HPV) testing into the UK cervical cancer screening programme. These include options that incorporate HPV testing either as a triage for mild and borderline smear abnormalities or as a primary screening test. Outcomes include the predicted impact on resource use, total cost, life years and cost-effectiveness. Extensive sensitivity analysis has been carried out to explore the importance of the uncertainty associated with disease natural history and the impact of screening. Under baseline assumptions, the cost-effectiveness of different options for introducing LBC appears favourable, and these results are consistent under a range of assumptions for its impact on the diagnostic effectiveness of cytology. However, if we assume a higher marginal cost of LBC in comparison to conventional methods, primary smear testing options are predicted to be more cost-effective without LBC. Combined LBC primary smear and HPV testing with a 5-year interval is similar in both cost and effectiveness to the other 3-yearly options of primary smear testing or primary HPV testing alone. However, both primary HPV testing and combined options would give rise to a far greater risk of inappropriate colposcopy throughout a woman's lifetime. British Journal of Cancer (2004) 91, 84-91. doi:10.1038/sj.bjc.6601884 www.bjcancer.com Published online 25 May 2004
Project description:This study aims to inform herpes simplex virus type 2 (HSV-2) vaccine development, licensure, and implementation by delineating the population-level impact of vaccination. Mathematical models were constructed to describe the transmission dynamics in presence of prophylactic or therapeutic vaccines assuming 50% efficacy, with application to the United States. Catch-up prophylactic vaccination will reduce, by 2050, annual number of new infections by 58%, incidence rate by 60%, seroprevalence by 21%, and avert yearly as much as 350,000 infections. Number of vaccinations needed to avert one infection was only 50 by 2050, 34 by prioritizing those aged 15-19 years, 4 by prioritizing the highest sexual risk group, 43 by prioritizing women, and 47 by prioritizing men. Therapeutic vaccination of infected adults with symptomatic disease will reduce, by 2050, annual number of new infections by 12%, incidence rate by 13%, seroprevalence by 4%, and avert yearly as much as 76,000 infections. Number of vaccinations needed to avert one infection was eight by 2050, two by prioritizing those aged 15-19 years, three by prioritizing the highest sexual risk group, seven by prioritizing men, and ten by prioritizing women. HSV-2 vaccination offers an impactful and cost-effective intervention to prevent genital herpes medical and psychosexual disease burden.
Project description:BACKGROUND:Sweden revised their cervical cancer screening program in 2017 to include cytology-based screening for women aged 23-29 years and primary human papillomavirus (HPV) testing for women aged 30-64 years; however, alternative strategies may be preferred. To inform cervical cancer prevention policies for unvaccinated women, we evaluated the cost-effectiveness of alternative screening strategies, including the current Swedish guidelines. METHODS:We adapted a mathematical simulation model of HPV and cervical cancer to the Swedish context using primary epidemiologic data. We compared the cost-effectiveness of alternative screening strategies that varied by the age to start screening, the age to switch from cytology to HPV testing, HPV strategies not preceded by cytology, screening frequency, and management of HPV-positive/cytology-negative women. RESULTS:We found that the current Swedish guidelines were more costly and less effective than alternative primary HPV-based strategies. All cost-efficient strategies involved primary HPV testing not preceded by cytology for younger women. Given a cost-effectiveness threshold of €85,619 per quality-adjusted life year gained, the optimal strategy involved 5-yearly primary HPV-based screening for women aged 23-50 years and 10-yearly HPV-based screening for women older than age 50 years. CONCLUSIONS:Primary screening based on HPV alone may be considered for unvaccinated women for those countries with similar HPV burdens.
Project description:<h4>Background</h4>Chlamydia screening programmes have been implemented in several countries, but the effects of screening on incidence, prevalence, and reproductive sequelae remain unclear. In England, despite increases in testing with the rollout of the National Chlamydia Screening Programme (NCSP; 2003-08), prevalence estimated in 10-yearly population-based surveys was similar before (1999-2001) and after (2010-12) the programme. However, the precision of these previous estimates was limited by the low numbers of infections. We aimed to establish annual, rather than 10-yearly, estimates of chlamydia prevalence and infection duration.<h4>Methods</h4>In this model-based analysis, we used previously published minimum and maximum estimates and Public Health England data for chlamydia test coverage and diagnoses in men and women aged 15-24 years in England, before, during, and after the scale-up of national chlamydia screening. We used a mechanistic model, which accounted for symptomatic chlamydia testing and asymptomatic screening, to estimate changes in prevalence and average duration of infections for each year. We describe estimates derived from the maximum and minimum numbers of tests and diagnoses as maximum and minimum estimates, regardless of their relative magnitude.<h4>Findings</h4>The data included numbers of tests and diagnoses in men and women aged 15-19 years and 20-24 years in England each year from 2000 to 2015. We estimated reductions in prevalence and average infection duration in both sexes once screening was fully implemented. From 2008 to 2010, estimated posterior median prevalence reductions in people aged 15-24 years were 0·68 percentage points (95% credible interval 0·26-1·40; minimum) and 0·66 percentage points (0·25-1·37; maximum) for men and 0·77 percentage points (0·45-1·27) for women (minimum and maximum estimates were the same for women). Over the same time period, mean duration of infection reduced by 75 days (95% credible interval 17-255; minimum) and 74 days (95% credible interval 17-247; maximum) in men and 30 days (22-40) in women. Since 2010, some of the progress made by the NCSP has been reversed, alongside a reduction in testing.<h4>Interpretation</h4>Our analysis provides the first evidence for a reduction in chlamydia prevalence in England concurrent with large-scale population testing. It also shows a consistent decline in the average duration of infections, which is a measure of screening effectiveness that is unaffected by behavioural changes.<h4>Funding</h4>National Institute for Health Research, Medical Research Council.
Project description:Cervical cancer is widely preventable through screening, but little is known about the duration of protection offered by a negative screen in North America. A case-control study was conducted with records from population-based registries in New Mexico. Cases were women diagnosed with cervical cancer in 2006-2016, obtained from the Tumor Registry. Five controls per case from the New Mexico HPV Pap Registry were matched to cases by sex, age and place of residence. Dates and results of all cervical screening and diagnostic tests since 2006 were identified from the pap registry. We estimated the odds ratio of nonlocalized (Stage II+) and localized (Stage I) cervical cancer associated with attending screening in the 3 years prior to case-diagnosis compared to women not screened in 5 years. Of 876 cases, 527 were aged 25-64 years with ≥3 years of potential screening data. Only 38% of cases and 61% of controls attended screening in a 3-year period. Women screened in the 3 years prior to diagnosis had 83% lower risk of nonlocalized cancer (odds ratio [OR] = 0.17, 95% CI: 0.12-0.24) and 48% lower odds of localized cancer (OR = 0.52, 95% CI: 0.38-0.72), compared to women not screened in the 5 years prior to diagnosis. Women remained at low risk of nonlocalized cancer for 3.5-5 years after a negative screen compared to women with no negative screens in the 5 years prior to diagnosis. Routine cervical screening is effective at preventing localized and nonlocalized cervical cancers; 3 yearly screening prevents 83% of nonlocalized cancers, with no additional benefit of more frequent screening. Increasing screening coverage remains essential to further reduce cervical cancer incidence.
Project description:Background:Biennial screening is generally recommended for average-risk women aged 50 to 74 years, but tailored screening may provide greater benefits. Objective:To estimate outcomes for various screening intervals after age 50 years based on breast density and risk for breast cancer. Design:Collaborative simulation modeling using national incidence, breast density, and screening performance data. Setting:United States. Patients:Women aged 50 years or older with various combinations of breast density and relative risk (RR) of 1.0, 1.3, 2.0, or 4.0. Intervention:Annual, biennial, or triennial digital mammography screening from ages 50 to 74 years (vs. no screening) and ages 65 to 74 years (vs. biennial digital mammography from ages 50 to 64 years). Measurements:Lifetime breast cancer deaths, life expectancy and quality-adjusted life-years (QALYs), false-positive mammograms, benign biopsy results, overdiagnosis, cost-effectiveness, and ratio of false-positive results to breast cancer deaths averted. Results:Screening benefits and overdiagnosis increase with breast density and RR. False-positive mammograms and benign results on biopsy decrease with increasing risk. Among women with fatty breasts or scattered fibroglandular density and an RR of 1.0 or 1.3, breast cancer deaths averted were similar for triennial versus biennial screening for both age groups (50 to 74 years, median of 3.4 to 5.1 vs. 4.1 to 6.5 deaths averted; 65 to 74 years, median of 1.5 to 2.1 vs. 1.8 to 2.6 deaths averted). Breast cancer deaths averted increased with annual versus biennial screening for women aged 50 to 74 years at all levels of breast density and an RR of 4.0, and those aged 65 to 74 years with heterogeneously or extremely dense breasts and an RR of 4.0. However, harms were almost 2-fold higher. Triennial screening for the average-risk subgroup and annual screening for the highest-risk subgroup cost less than $100 000 per QALY gained. Limitation:Models did not consider women younger than 50 years, those with an RR less than 1, or other imaging methods. Conclusion:Average-risk women with low breast density undergoing triennial screening and higher-risk women with high breast density receiving annual screening will maintain a similar or better balance of benefits and harms than average-risk women receiving biennial screening. Primary Funding Source:National Cancer Institute.
Project description:We compared the long-term impact of 1- and 2-year screening mammography intervals using prognostic, screening, and outcome information for women aged 50-74 years obtained from the Screening Mammography Program of British Columbia in two time periods, prior to 1997 (policy of annual mammography) and after 1997 (biennial mammography). Survival was estimated for both periods using a prognostic model and the expected rate of interval and screen-detected cancers. The likelihood of a screen-detected cancer with annual screening was 2.32 per thousand screens and with biennial screening was 3.32 per thousand screens. The prognostic profile of screen-detected cancers was better than that of interval cancers. Among both screen-detected and interval cancers, the prognostic profiles with annual and biennial screening were similar. The estimated breast cancer-specific survival rates for women undergoing annual and biennial screening mammography were 95.2 and 94.6% at 5 years, and 90.4 and 89.2% at 10 years, respectively. Annual compared to biennial mammography was associated with a 1.2% increase in the estimated 10-year breast cancer-specific survival for women aged 50-74 years, diagnosed with invasive breast cancer after screening programme attendance.
Project description:BACKGROUND:New Zealand (NZ) is considering transitioning from 3-yearly cervical cytology screening in women 20-69 years (current practice) to primary HPV screening. We evaluated HPV-based screening in both HPV-unvaccinated women and cohorts offered HPV vaccination in New Zealand (vaccination coverage ~50%). METHODS:A complex model of HPV transmission, vaccination, cervical screening, and invasive cervical cancer was extensively validated against national population-based datasets. Sixteen potential strategies for HPV screening were considered. RESULTS:Most primary HPV strategies were more effective than current practice, for both unvaccinated women and cohorts offered vaccination. The optimal strategy for both groups was 5-yearly HPV screening in women aged 25-69 years with partial genotyping for HPV 16/18 and referral to colposcopy, and cytological triage of other oncogenic types. This is predicted to reduce cervical cancer incidence and mortality by a further 12-16% and to save 4-13% annually in program costs (excluding overheads). The findings are sensitive to assumptions about future adherence to initiating screening at 25 years. CONCLUSION:Primary HPV screening with partial genotyping would be more effective and less costly than the current cytology-based screening program, in both unvaccinated women and cohorts offered vaccination. These findings have been considered in a review of cervical screening in NZ.
Project description:<h4>Objective</h4>To evaluate and compare annual and biennial mammography screening rates across age, race, and geographic location (rural-urban) and to determine mammography screening persistence over 10 years among women enrolled in the West Virginia (WV) Medicaid Fee-for-Service (FFS) program.<h4>Methods</h4>The WV Medicaid FFS administrative claims data for women recipients aged 40-64 from 1999 to 2008 were used for study purposes. Annual and biennial screening rates and persistence with screening were determined for women who were continuously enrolled in the WV Medicaid FFS program for respective calendar years.<h4>Results</h4>A steady decline in the annual and biennial screening rates over a 10-year period (1999-2008) was observed among women recipients aged 40-64 years in the WV Medicaid FFS program, and screening persistence was also lower. Both annual and biennial screening rates and persistence varied by different demographic characteristics.<h4>Conclusions</h4>Although mammography screening services are covered under Medicaid programs, underuse persists as a major concern. The results of this study emphasize the need to identify and address barriers to mammography screening in low-income rural populations.
Project description:BACKGROUND: Gastric cancer (GC) surveillance based on oesophagogastroduodenoscopy (OGD) appears to be a promising strategy for GC prevention. By evaluating the cost-effectiveness of endoscopic surveillance in Singaporean Chinese, this study aimed to inform the implementation of such a program in a population with a low to intermediate GC risk. METHODS: USING A REFERENCE STRATEGY OF NO OGD INTERVENTION, WE EVALUATED FOUR STRATEGIES: 2-yearly OGD surveillance, annual OGD surveillance, 2-yearly OGD screening and 2-yearly screening plus annual surveillance in Singaporean Chinese aged 50-69 years. From a perspective of the healthcare system, Markov models were built to simulate the life experience of the target population. The models projected discounted lifetime costs ($), quality adjusted life year (QALY), and incremental cost-effectiveness ratio (ICER) indicating the cost-effectiveness of each strategy against a Singapore willingness-to-pay of $46,200/QALY. Deterministic and probabilistic sensitivity analyses were used to identify the influential variables and their associated thresholds, and to quantify the influence of parameter uncertainties respectively. RESULTS: With an ICER of $44,098/QALY, the annual OGD surveillance was the optimal strategy while the 2-yearly surveillance was the most cost-effective strategy (ICER = $25,949/QALY). The screening-based strategies were either extendedly dominated or cost-ineffective. The cost-effectiveness heterogeneity of the four strategies was observed across age-gender subgroups. Eight influential parameters were identified each with their specific thresholds to define the choice of optimal strategy. Accounting for the model uncertainties, the probability that the annual surveillance is the optimal strategy in Singapore was 44.5%. CONCLUSION: Endoscopic surveillance is potentially cost-effective in the prevention of GC for populations at low to intermediate risk. Regarding program implementation, a detailed analysis of influential factors and their associated thresholds is necessary. Multiple strategies should be considered in order to recommend the right strategy for the right population.