Causal Estimation of Long-term Intervention Cost-effectiveness Using Genetic Instrumental Variables: An Application to Cancer.

BACKGROUND: This article demonstrates a means of assessing long-term intervention cost-effectiveness in the absence of data from randomized controlled trials and without recourse to Markov simulation or similar types of cohort simulation. METHODS: Using a Mendelian randomization study design, we developed causal estimates of the genetically predicted effect of bladder, breast, colorectal, lung, multiple myeloma, ovarian, prostate, and thyroid cancers on health care costs and quality-adjusted life-years (QALYs) using outcome data drawn from the UK Biobank cohort. We then used these estimates in a simulation model to estimate the cost-effectiveness of a hypothetical population-wide preventative intervention based on a repurposed class of antidiabetic drugs known as sodium-glucose cotransporter-2 (SGLT2) inhibitors very recently shown to reduce the odds of incident prostate cancer. RESULTS: Genetic liability to prostate cancer and breast cancer had material causal impacts on either or both health care costs and QALYs. Mendelian randomization results for the less common cancers were associated with considerable uncertainty. SGLT2 inhibition was unlikely to be a cost-effective preventative intervention for prostate cancer, although this conclusion depended on the price at which these drugs would be offered for a novel anticancer indication. IMPLICATIONS: Our new causal estimates of cancer exposures on health economic outcomes may be used as inputs into decision-analytic models of cancer interventions such as screening programs or simulations of longer-term outcomes associated with therapies investigated in randomized controlled trials with short follow-ups. Our method allowed us to rapidly and efficiently estimate the cost-effectiveness of a hypothetical population-scale anticancer intervention to inform and complement other means of assessing long-term intervention value. HIGHLIGHTS: The article demonstrates a novel method of assessing long-term intervention cost-effectiveness without relying on randomized controlled trials or cohort simulations.Mendelian randomization was used to estimate the causal effects of certain cancers on health care costs and quality-adjusted life-years (QALYs) using data from the UK Biobank cohort.Given causal data on the association of different cancer exposures on costs and QALYs, it was possible to simulate the cost-effectiveness of an anticancer intervention.Genetic liability to prostate cancer and breast cancer significantly affected health care costs and QALYs, but the hypothetical intervention using SGLT2 inhibitors for prostate cancer may not be cost-effective, depending on the drug's price for the new anticancer indication. The methods we propose and implement can be used to efficiently estimate intervention cost-effectiveness and to inform decision making in all manner of preventative and therapeutic contexts.

Impact of PSA testing on secondary care costs in England and Wales: estimates from the Cluster randomised triAl of PSA testing for Prostate cancer (CAP).

BACKGROUND: Screening men for prostate cancer using prostate-specific antigen (PSA) testing remains controversial. We aimed to estimate the likely budgetary impact on secondary care in England and Wales to inform screening decision makers. METHODS: The Cluster randomised triAl of PSA testing for Prostate cancer study (CAP) compared a single invitation to men aged 50-69 for a PSA test with usual care (no screening). Routinely collected hospital care data were obtained for all men in CAP, and NHS reference costs were mapped to each event via Healthcare Resource Group (HRG) codes. Secondary-care costs per man per year were calculated, and cost differences (and population-level estimates) between arms were derived annually for the first five years following randomisation. RESULTS: In the first year post-randomisation, secondary-care costs averaged across all men (irrespective of a prostate cancer diagnosis) in the intervention arm (n = 189279) were £44.80 (95% confidence interval: £18.30-£71.30) higher than for men in the control arm (n = 219357). Extrapolated to a population level, the introduction of a single PSA screening invitation could lead to additional secondary care costs of £314 million. CONCLUSIONS: Introducing a single PSA screening test for men aged 50-69 across England and Wales could lead to very high initial secondary-care costs.

Cost-Effectiveness Analysis of Prostate Cancer Screening in the UK: A Decision Model Analysis Based on the CAP Trial.

BACKGROUND AND OBJECTIVE: Most guidelines in the UK, Europe and North America do not recommend organised population-wide screening for prostate cancer. Prostate-specific antigen-based screening can reduce prostate cancer-specific mortality, but there are concerns about overdiagnosis, overtreatment and economic value. The aim was therefore to assess the cost effectiveness of eight potential screening strategies in the UK. METHODS: We used a cost-utility analysis with an individual-based simulation model. The model was calibrated to data from the 10-year follow-up of the Cluster Randomised Trial of PSA Testing for Prostate Cancer (CAP). Treatment effects were modelled using data from the Prostate Testing for Cancer and Treatment (ProtecT) trial. The participants were a hypothetical population of 10 million men in the UK followed from age 30 years to death. The strategies were: no screening; five age-based screening strategies; adaptive screening, where men with an initial prostate-specific antigen level of < 1.5 ng/mL are screened every 6 years and those above this level are screened every 4 years; and two polygenic risk-stratified screening strategies. We assumed the use of pre-biopsy multi-parametric magnetic resonance imaging for men with prostate-specific antigen ≥ 3 ng/mL and combined transrectal ultrasound-guided and targeted biopsies. The main outcome measures were projected lifetime costs and quality-adjusted life-years from a National Health Service perspective. RESULTS: All screening strategies increased costs compared with no screening, with the majority also increasing quality-adjusted life-years. At willingness-to-pay thresholds of £20,000 or £30,000 per quality-adjusted life-year gained, a once-off screening at age 50 years was optimal, although this was sensitive to the utility estimates used. Although the polygenic risk-stratified screening strategies were not on the cost-effectiveness frontier, there was evidence to suggest that they were less cost ineffective than the alternative age-based strategies. CONCLUSIONS: Of the prostate-specific antigen-based strategies compared, only a once-off screening at age 50 years was potentially cost effective at current UK willingness-to-pay thresholds. An additional follow-up of CAP to 15 years may reduce uncertainty about the cost effectiveness of the screening strategies.

Can polygenic risk scores contribute to cost-effective cancer screening? A systematic review.

PURPOSE: Polygenic risk influences susceptibility to cancer. We assessed whether polygenic risk scores could be used in conjunction with other predictors of future disease status in cost-effective risk-stratified screening for cancer. METHODS: We undertook a systematic review of papers that evaluated the cost-effectiveness of screening interventions informed by polygenic risk scores compared with more conventional screening modalities. We included papers reporting cost-effectiveness outcomes with no restriction on type of cancer or form of polygenic risk modeled. We evaluated studies using the Quality of Health Economic Studies checklist. RESULTS: A total of 10 studies were included in the review, which investigated 3 cancers: prostate (n = 5), colorectal (n = 3), and breast (n = 2). Of the 10 papers, 9 scored highly (score >75 on a 0-100 scale) when assessed using the quality checklist. Of the 10 studies, 8 concluded that polygenic risk-informed cancer screening was likely to be more cost-effective than alternatives. CONCLUSION: Despite the positive conclusions of the included studies, it is unclear if polygenic risk stratification will contribute to cost-effective cancer screening given the absence of robust evidence on the costs of polygenic risk stratification, the effects of differential ancestry, potential downstream economic sequalae, and how large volumes of polygenic risk data would be collected and used.

Investigating the effect of sexual behaviour on oropharyngeal cancer risk: a methodological assessment of Mendelian randomization.

BACKGROUND: Human papilloma virus infection is known to influence oropharyngeal cancer (OPC) risk, likely via sexual transmission. However, sexual behaviour has been correlated with other risk factors including smoking and alcohol, meaning independent effects are difficult to establish. We aimed to evaluate the causal effect of sexual behaviour on the risk of OPC using Mendelian randomization (MR). METHODS: Genetic variants robustly associated with age at first sex (AFS) and the number of sexual partners (NSP) were used to perform both univariable and multivariable MR analyses with summary data on 2641 OPC cases and 6585 controls, obtained from the largest available genome-wide association studies (GWAS). Given the potential for genetic pleiotropy, we performed a number of sensitivity analyses: (i) MR methods to account for horizontal pleiotropy, (ii) MR of sexual behaviours on positive (cervical cancer and seropositivity for Chlamydia trachomatis) and negative control outcomes (lung and oral cancer), (iii) Causal Analysis Using Summary Effect estimates (CAUSE), to account for correlated and uncorrelated horizontal pleiotropic effects, (iv) multivariable MR analysis to account for the effects of smoking, alcohol, risk tolerance and educational attainment. RESULTS: In univariable MR, we found evidence supportive of an effect of both later AFS (IVW OR = 0.4, 95%CI (0.3, 0.7), per standard deviation (SD), p = < 0.001) and increasing NSP (IVW OR = 2.2, 95%CI (1.3, 3.8) per SD, p = < 0.001) on OPC risk. These effects were largely robust to sensitivity analyses accounting for horizontal pleiotropy. However, negative control analysis suggested potential violation of the core MR assumptions and subsequent CAUSE analysis implicated pleiotropy of the genetic instruments used to proxy sexual behaviours. Finally, there was some attenuation of the univariable MR results in the multivariable models (AFS IVW OR = 0.7, 95%CI (0.4, 1.2), p = 0.21; NSP IVW OR = 0.9, 95%CI (0.5 1.7), p = 0.76). CONCLUSIONS: Despite using genetic variants strongly related sexual behaviour traits in large-scale GWAS, we found evidence for correlated pleiotropy. This emphasizes a need for multivariable approaches and the triangulation of evidence when performing MR of complex behavioural traits.

Systematic Review of Cost-Effectiveness Models in Prostate Cancer: Exploring New Developments in Testing and Diagnosis.

OBJECTIVES: Recent innovations in prostate cancer diagnosis include new biomarkers and more accurate biopsy methods. This study assesses the evidence base on cost-effectiveness of these developments (eg, Prostate Health Index and magnetic resonance imaging [MRI]-guided biopsy) and identifies areas of improvement for future cost-effectiveness models. METHODS: A systematic review using the National Health Service Economic Evaluation Database, MEDLINE, Embase, Health Technology Assessment databases, National Institute for Health and Care Excellence guidelines, and United Kingdom National Screening Committee guidance was performed, between 2009 and 2021. Relevant data were extracted on study type, model inputs, modeling methods and cost-effectiveness conclusions, and results narratively synthesized. RESULTS: A total of 22 model-based economic evaluations were included. A total of 11 compared the cost-effectiveness of new biomarkers to prostate-specific antigen testing alone and all found biomarkers to be cost saving. A total of 8 compared MRI-guided biopsy methods to transrectal ultrasound-guided methods and found MRI-guided methods to be most cost-effective. Newer detection methods showed a reduction in unnecessary biopsies and overtreatment. The most cost-effective follow-up strategy in men with a negative initial biopsy was uncertain. Many studies did not model for stage or grade of cancer, cancer progression, or the entire testing and treatment pathway. Few fully accounted for uncertainty. CONCLUSIONS: This review brings together the cost-effectiveness literature for novel diagnostic methods in prostate cancer, showing that most studies have found new methods to be more cost-effective than standard of care. Several limitations of the models were identified, however, limiting the reliability of the results. Areas for further development include accurately modeling the impact of early diagnostic tests on long-term outcomes of prostate cancer and fully accounting for uncertainty.

Quantitative Bias Analysis of the Association between Occupational Radiation Exposure and Ischemic Heart Disease Mortality in UK Nuclear Workers.

The scientific question of whether protracted low-dose or low-dose-rate exposure to external radiation is causally related to the risk of circulatory disease continues to be an important issue for radiation protection. Previous analyses of a matched case-control dataset nested in a large cohort of UK nuclear fuel cycle workers indicated that there was little evidence that observed associations between external radiation dose and ischemic heart disease (IHD) mortality risk [OR = 1.35 (95% CI: 0.99-1.84) for 15-year-lagged exposure] could alternatively be explained by confounding from pre-employment tobacco smoking, BMI or blood pressure, or from socioeconomic status or occupational exposure to excessive noise or shiftwork. To improve causal inference about the observed external radiation dose and IHD mortality association, we estimated the potential magnitude and direction of non-random errors, incorporated sensitivity analyses and simulated bias effects under plausible scenarios. We conducted quantitative bias analyses of plausible scenarios based on 1,000 Monte Carlo samples to explore the impact of exposure measurement error, missing information on tobacco smoking, and unmeasured confounding, and assessed whether observed associations were reliant on the inclusion of specific matched pairs using bootstrapping with 10% of matched pairs randomly excluded in 1,000 samples. We further explored the plausibility that having been monitored for internal exposure, which was an important confounding factor in the case-control analysis for which models were adjusted, was indeed a confounding factor or whether it might have been the result of some form of selection bias. Consistent with the broader epidemiological evidence-base, these analyses provide further evidence that the dose-response association between cumulative external radiation exposure and IHD mortality is non-linear in that it has a linear shape plateauing at an excess risk of 43% (95% CI: 7-92%) on reaching 390 mSv. Analyses of plausible scenarios of patterns of missing data for tobacco smoking at start of employment indicated that this resulted in relatively little bias towards the null in the original analysis. An unmeasured confounder would have had to have been highly correlated (rp > 0.60) with cumulative external radiation dose to importantly bias observed associations. The confounding effect of "having been monitored for internal dose" was unlikely to have been a true confounder in a biological sense, but instead may have been some unknown factor related to differences over time and between sites in selection criteria for internal monitoring, possibly resulting in collider bias. Plausible patterns of exposure measurement error negatively biased associations regardless of the modeled scenario, but did not importantly change the shape of the observed dose-response associations. These analyses provide additional support for the hypothesis that the observed association between external radiation exposure and IHD mortality may be causal.

Using a Modified Delphi Approach to Gain Consensus on Relevant Comparators in a Cost-Effectiveness Model: Application to Prostate Cancer Screening.

OBJECTIVE: Challenges can exist when framing the decision question in a cost-effectiveness analysis, particularly when there is disagreement among experts on relevant comparators. Using prostate cancer screening and recent developments in risk stratification, early-detection biomarkers, and diagnostic technologies as a case study, we report a modified Delphi approach to handle decision-question uncertainty. METHODS: The study involved two rounds of anonymous online questionnaires to identify the prostate cancer screening strategies that international researchers, clinicians and decision makers felt important to consider in a cost-effectiveness model. Both purposive and snowball sampling were used to recruit experts. The questionnaire was based on a review of the literature and was piloted for language, comprehension and ease of use prior to dissemination. In Round 1, respondents indicated their preferred screening strategy (including no screening) through a series of multiple-choice questions. The responses informed a set of 13 consensus statements, which respondents ranked their agreement with on a 9-point Likert scale (Round 2). Consensus was considered reached if > 70% of participants indicated agreement and < 15% indicated disagreement. RESULTS: Twenty participants completed Round 1 and 17 completed Round 2. Consensus was shown towards comparing no formal screening, age-based, and risk-based strategies. The risk-based approaches included screening only higher-risk men, using shorter screening intervals for higher-risk men, screening higher-risk men at an earlier age, and tailoring screening intervals based on prostate-specific antigen (PSA) level at a previous test. There was agreement that inclusion of MRI in the pathway should be considered, but disagreement on the inclusion of new biomarkers. CONCLUSION: In disease areas where technologies are rapidly evolving, a modified Delphi approach provides a useful tool to identify relevant comparators in an economic evaluation.

Active monitoring, radical prostatectomy and radical radiotherapy in PSA-detected clinically localised prostate cancer: the ProtecT three-arm RCT.

BACKGROUND: Prostate cancer is the most common cancer among men in the UK. Prostate-specific antigen testing followed by biopsy leads to overdetection, overtreatment as well as undertreatment of the disease. Evidence of treatment effectiveness has lacked because of the paucity of randomised controlled trials comparing conventional treatments. OBJECTIVES: To evaluate the effectiveness of conventional treatments for localised prostate cancer (active monitoring, radical prostatectomy and radical radiotherapy) in men aged 50-69 years. DESIGN: A prospective, multicentre prostate-specific antigen testing programme followed by a randomised trial of treatment, with a comprehensive cohort follow-up. SETTING: Prostate-specific antigen testing in primary care and treatment in nine urology departments in the UK. PARTICIPANTS: Between 2001 and 2009, 228,966 men aged 50-69 years received an invitation to attend an appointment for information about the Prostate testing for cancer and Treatment (ProtecT) study and a prostate-specific antigen test; 82,429 men were tested, 2664 were diagnosed with localised prostate cancer, 1643 agreed to randomisation to active monitoring (n = 545), radical prostatectomy (n = 553) or radical radiotherapy (n = 545) and 997 chose a treatment. INTERVENTIONS: The interventions were active monitoring, radical prostatectomy and radical radiotherapy. TRIAL PRIMARY OUTCOME MEASURE: Definite or probable disease-specific mortality at the 10-year median follow-up in randomised participants. SECONDARY OUTCOME MEASURES: Overall mortality, metastases, disease progression, treatment complications, resource utilisation and patient-reported outcomes. RESULTS: There were no statistically significant differences between the groups for 17 prostate cancer-specific (p = 0.48) and 169 all-cause (p = 0.87) deaths. Eight men died of prostate cancer in the active monitoring group (1.5 per 1000 person-years, 95% confidence interval 0.7 to 3.0); five died of prostate cancer in the radical prostatectomy group (0.9 per 1000 person-years, 95% confidence interval 0.4 to 2.2 per 1000 person years) and four died of prostate cancer in the radical radiotherapy group (0.7 per 1000 person-years, 95% confidence interval 0.3 to 2.0 per 1000 person years). More men developed metastases in the active monitoring group than in the radical prostatectomy and radical radiotherapy groups: active monitoring, n = 33 (6.3 per 1000 person-years, 95% confidence interval 4.5 to 8.8); radical prostatectomy, n = 13 (2.4 per 1000 person-years, 95% confidence interval 1.4 to 4.2 per 1000 person years); and radical radiotherapy, n = 16 (3.0 per 1000 person-years, 95% confidence interval 1.9 to 4.9 per 1000 person-years; p = 0.004). There were higher rates of disease progression in the active monitoring group than in the radical prostatectomy and radical radiotherapy groups: active monitoring (n = 112; 22.9 per 1000 person-years, 95% confidence interval 19.0 to 27.5 per 1000 person years); radical prostatectomy (n = 46; 8.9 per 1000 person-years, 95% confidence interval 6.7 to 11.9 per 1000 person-years); and radical radiotherapy (n = 46; 9.0 per 1000 person-years, 95% confidence interval 6.7 to 12.0 per 1000 person years; p < 0.001). Radical prostatectomy had the greatest impact on sexual function/urinary continence and remained worse than radical radiotherapy and active monitoring. Radical radiotherapy's impact on sexual function was greatest at 6 months, but recovered somewhat in the majority of participants. Sexual and urinary function gradually declined in the active monitoring group. Bowel function was worse with radical radiotherapy at 6 months, but it recovered with the exception of bloody stools. Urinary voiding and nocturia worsened in the radical radiotherapy group at 6 months but recovered. Condition-specific quality-of-life effects mirrored functional changes. No differences in anxiety/depression or generic or cancer-related quality of life were found. At the National Institute for Health and Care Excellence threshold of £20,000 per quality-adjusted life-year, the probabilities that each arm was the most cost-effective option were 58% (radical radiotherapy), 32% (active monitoring) and 10% (radical prostatectomy). LIMITATIONS: A single prostate-specific antigen test and transrectal ultrasound biopsies were used. There were very few non-white men in the trial. The majority of men had low- and intermediate-risk disease. Longer follow-up is needed. CONCLUSIONS: At a median follow-up point of 10 years, prostate cancer-specific mortality was low, irrespective of the assigned treatment. Radical prostatectomy and radical radiotherapy reduced disease progression and metastases, but with side effects. Further work is needed to follow up participants at a median of 15 years. TRIAL REGISTRATION: Current Controlled Trials ISRCTN20141297. FUNDING: This project was funded by the National Institute for Health Research Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 24, No. 37. See the National Institute for Health Research Journals Library website for further project information.

Prostate cancer is the most common cancer in men and is often found through a blood test called a prostate-specific antigen test and through biopsies of the prostate. Over the years, these tests led to the detection of many small cancers that do not cause harm. Some prostate cancers are harmful, but it is difficult to recognise them early. When cancer is still inside the prostate, the conventional treatments are surgery or radiotherapy, which carry side effects including leaking urine and difficulty getting an erection, so another option is repeat investigations at regular intervals (active monitoring), with treatments given if the cancer progresses. These options needed to be compared in a study called a 'randomised trial' in which men agree to be allocated to one of the three treatments. In the Prostate testing for cancer and Treatment (ProtecT) study, 200,000 men aged 50­69 years were invited to have a prostate-specific antigen test. Of the 82,849 men who agreed to be tested, 1643 of whom had prostate cancer that was still contained in the prostate agreed to be allocated to one of the three treatments. After an average of 10 years of follow-up, 99% of men were alive in each of the treatment groups. However, when compared with active monitoring, surgery and radiotherapy reduced the risk of disease spreading outside the prostate by half. Patients reported that urinary leakage and sexual function were worst with surgery, and sexual and bowel functions were affected by radiotherapy. Men on active monitoring had a gradual decline in their urinary and sexual function, particularly as around half of them later had surgery or radiotherapy. Radiotherapy was the treatment that seemed to be the best value for money. The findings from the Prostate testing for cancer and Treatment (ProtecT) study can help men make decisions about being tested and which treatment to have if they are found to have cancer within the prostate. We now need to find out the longer-term effects of these treatments on how long men live and their quality of life.

The ProtecT randomised trial cost-effectiveness analysis comparing active monitoring, surgery, or radiotherapy for prostate cancer.

BACKGROUND: There is limited evidence relating to the cost-effectiveness of treatments for localised prostate cancer. METHODS: The cost-effectiveness of active monitoring, surgery, and radiotherapy was evaluated within the Prostate Testing for Cancer and Treatment (ProtecT) randomised controlled trial from a UK NHS perspective at 10 years' median follow-up. Prostate cancer resource-use collected from hospital records and trial participants was valued using UK reference-costs. QALYs (quality-adjusted-life-years) were calculated from patient-reported EQ-5D-3L measurements. Adjusted mean costs, QALYs, and incremental cost-effectiveness ratios were calculated; cost-effectiveness acceptability curves and sensitivity analyses addressed uncertainty; subgroup analyses considered age and disease-risk. RESULTS: Adjusted mean QALYs were similar between groups: 6.89 (active monitoring), 7.09 (radiotherapy), and 6.91 (surgery). Active monitoring had lower adjusted mean costs (£5913) than radiotherapy (£7361) and surgery (£7519). Radiotherapy was the most likely (58% probability) cost-effective option at the UK NICE willingness-to-pay threshold (£20,000 per QALY). Subgroup analyses confirmed radiotherapy was cost-effective for older men and intermediate/high-risk disease groups; active monitoring was more likely to be the cost-effective option for younger men and low-risk groups. CONCLUSIONS: Longer follow-up and modelling are required to determine the most cost-effective treatment for localised prostate cancer over a man's lifetime. TRIAL REGISTRATION: Current Controlled Trials number, ISRCTN20141297: http://isrctn.org (14/10/2002); ClinicalTrials.gov number, NCT02044172: http://www.clinicaltrials.gov (23/01/2014).

Varenicline versus nicotine replacement therapy for long-term smoking cessation: an observational study using the Clinical Practice Research Datalink.

BACKGROUND: Smoking is the leading avoidable cause of illness and premature mortality. The first-line treatments for smoking cessation are nicotine replacement therapy and varenicline. Meta-analyses of experimental studies have shown that participants allocated to the varenicline group were 1.57 times (95% confidence interval 1.29 to 1.91 times) as likely to be abstinent 6 months after treatment as those allocated to the nicotine replacement therapy group. However, there is limited evidence about the effectiveness of varenicline when prescribed in primary care. We investigated the effectiveness and rate of adverse events of these medicines in the general population. OBJECTIVE: To estimate the effect of prescribing varenicline on smoking cessation rates and health outcomes. DATA SOURCES: Clinical Practice Research Datalink. METHODS: We conducted an observational cohort study using electronic medical records from the Clinical Practice Research Datalink. We extracted data on all patients who were prescribed varenicline or nicotine replacement therapy after 1 September 2006 who were aged ≥ 18 years. We investigated the effects of varenicline on smoking cessation, all-cause mortality and cause-specific mortality and hospitalisation for: (1) chronic lung disease, (2) lung cancer, (3) coronary heart disease, (4) pneumonia, (5) cerebrovascular disease, (6) diabetes, and (7) external causes; primary care diagnosis of myocardial infarction, chronic obstructive pulmonary disease, depression, or prescription for anxiety; weight in kg; general practitioner and hospital attendance. Our primary outcome was smoking cessation 2 years after the first prescription. We investigated the baseline differences between patients prescribed varenicline and patients prescribed nicotine replacement therapy. We report results using multivariable-adjusted, propensity score and instrumental variable regression. Finally, we developed methods to assess the relative bias of the different statistical methods we used. RESULTS: People prescribed varenicline were healthier at baseline than those prescribed nicotine replacement therapy in almost all characteristics, which highlighted the potential for residual confounding. Our instrumental variable analysis results found little evidence that patients prescribed varenicline had lower mortality 2 years after their first prescription (risk difference 0.67, 95% confidence interval -0.11 to 1.46) than those prescribed nicotine replacement therapy. They had similar rates of all-cause hospitalisation, incident primary care diagnoses of myocardial infarction and chronic obstructive pulmonary disease. People prescribed varenicline subsequently attended primary care less frequently. Patients prescribed varenicline were more likely (odds ratio 1.46, 95% confidence interval 1.42 to 1.50) to be abstinent 6 months after treatment than those prescribed nicotine replacement therapy when estimated using multivariable-adjusted for baseline covariates. Patients from more deprived areas were less likely to be prescribed varenicline. However, varenicline had similar effectiveness for these groups. CONCLUSION: Patients prescribed varenicline in primary care were more likely to quit smoking than those prescribed nicotine replacement therapy, but there was little evidence that they had lower rates of mortality or morbidity in the 4 years following the first prescription. There was little evidence of heterogeneity in effectiveness across the population. FUTURE WORK: Future research should investigate the decline in prescribing of smoking cessation products; develop an optimal treatment algorithm for smoking cessation; use methods for using instruments with survival outcomes; and develop methods for comparing multivariable-adjusted and instrumental variable estimates. LIMITATIONS: Not all of our code lists were validated, body mass index and Index of Multiple Deprivation had missing values, our results may suffer from residual confounding, and we had no information on treatment adherence. TRIAL REGISTRATION: This trial is registered as NCT02681848. FUNDING: This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 24, No. 9. See the NIHR Journals Library website for further project information.

Smoking is the number one avoidable cause of ill health and death. Experiments suggest that more smokers will quit after being given the drug varenicline than with any other smoking cessation treatment. However, most of the experiments used to license varenicline had a relatively short follow-up (< 1 year) and did not necessarily recruit participants who were representative of smokers seen in a general practice in the UK, who tend to be older, are sicker and more likely to have neuropsychiatric illnesses. In this study, we investigated the outcomes of 287,079 patients prescribed varenicline or nicotine replacement therapy (e.g. nicotine patches and gum). We followed each patient for up to 4 years after they received their prescriptions and matched their data to information on deaths from the Office for National Statistics and hospital admissions. We investigated how often these patients subsequently attended their general practitioner, and how often they received a diagnosis of myocardial infarction, chronic obstructive pulmonary disease, depression or anxiety in primary care. We found that patients who were prescribed varenicline were much more likely to quit smoking up to 4 years after they received treatment and subsequently attended their general practitioner less frequently. These findings were robust across the three different analysis methods we used. We also found that patients prescribed varenicline were much less likely to be ill or to die than those prescribed nicotine replacement therapy. However, these results may be because the patients who were prescribed varenicline were much healthier before they received the prescription. Therefore, these differences in health are unlikely to be caused by taking varenicline or quitting smoking. In conclusion, varenicline helped patients quit smoking, but there was little causal evidence that prescribing patients varenicline causally reduced rates of mortality or morbidity compared with prescribing nicotine replacement therapy.

Assessment of eating attitudes and dieting behaviors in healthy children: Confirmatory factor analysis of the Children's Eating Attitudes Test.

OBJECTIVE: The Children's Eating Attitudes Test (ChEAT) is a self-report questionnaire that is conventionally summarized with a single score to identify "problematic" eating attitudes, masking informative variability in different eating attitude domains. This study evaluated the empirical support for single- versus multifactor models of the ChEAT. For validation, we compared how well the single- versus multifactor-based scores predicted body mass index (BMI). METHOD: Using data from 13,674 participants of the 11.5 year-follow-up of the Promotion of Breastfeeding Intervention Trial (PROBIT) in the Republic of Belarus, we conducted confirmatory factor analysis to evaluate the performance of 3- and 5-factor models, which were based on past studies, to a single-factor model representing the conventional summary of the ChEAT. We used cross-validated linear regression models and the reduction in mean squared error (MSE) to compare the prediction of BMI at 11.5 and 16 years by the conventional and confirmed factor-based ChEAT scores. RESULTS: The 5-factor model, based on 14 of the original 26 ChEAT items, had good fit to the data whereas the 3- and single-factor models did not. The MSE for concurrent (11.5 years) BMI regressed on the 5-factor ChEAT summary was 35% lower than that of the single-score models, which reduced the MSE from the null model by only 1%-5%. The MSE for BMI at 16 years was 20% lower. DISCUSSION: We found that a parsimonious 5-factor model of the ChEAT explained the data collected from healthy Belarusian children better than the conventional summary score and thus provides a more discriminating measure of eating attitudes.

QMCPACK: an open source ab initio quantum Monte Carlo package for the electronic structure of atoms, molecules and solids.

QMCPACK is an open source quantum Monte Carlo package for ab initio electronic structure calculations. It supports calculations of metallic and insulating solids, molecules, atoms, and some model Hamiltonians. Implemented real space quantum Monte Carlo algorithms include variational, diffusion, and reptation Monte Carlo. QMCPACK uses Slater-Jastrow type trial wavefunctions in conjunction with a sophisticated optimizer capable of optimizing tens of thousands of parameters. The orbital space auxiliary-field quantum Monte Carlo method is also implemented, enabling cross validation between different highly accurate methods. The code is specifically optimized for calculations with large numbers of electrons on the latest high performance computing architectures, including multicore central processing unit and graphical processing unit systems. We detail the program's capabilities, outline its structure, and give examples of its use in current research calculations. The package is available at http://qmcpack.org.

Socioeconomic differences in childhood BMI trajectories in Belarus.

OBJECTIVE: To examine associations of parental socioeconomic position with early-life offspring body mass index (BMI) trajectories in a middle-income country. SUBJECTS: Overall, 12,385 Belarusian children born 1996-97 and enrolled in a randomised breastfeeding promotion trial at birth, with 3-14 measurements of BMI from birth to 7 years. METHODS: Cohort analysis in which exposures were parental education (common secondary or less; advanced secondary or partial university; completed university) and occupation (manual; non-manual) at birth, and the outcome was BMI z-score trajectories estimated using multilevel linear spline models, controlling for trial arm, location, parental BMI, maternal smoking status and number of older siblings. RESULTS: Infants born to university-educated mothers were heavier at birth than those born to secondary school-educated mothers [by 0.13 BMI z-score units (95% confidence interval, CI: 0.07, 0.19) for girls and 0.11 (95% CI: 0.05, 0.17) for boys; equivalent for an infant of average birth length to 43 and 38 g, respectively]. Between the ages of 3-7 years children of the most educated mothers had larger BMI increases than children of the least educated mothers. At age 7 years, after controlling for trial arm and location,  children of university-educated mothers had higher BMIs than those born to secondary school-educated mothers by 0.11 z-score (95% CI: 0.03, 0.19) among girls and 0.18 (95% CI: 0.1, 0.27) among boys, equivalent to differences in BMI for a child of average height of 0.19 and 0.26 kg/m2, respectively. After further controlling for parental BMI, these differences attenuated to 0.08 z-score (95% CI: 0, 0.16) and 0.16 z-score (95% CI: 0.07, 0.24), respectively, but changed very little after additional adjustment for number of older siblings and mother's smoking status. Associations were similar when based on paternal educational attainment and highest household occupation. CONCLUSIONS: In Belarus, consistent with some middle-income countries, higher socioeconomic position was associated with greater BMI trajectories from age 3 onwards.

Cost-effectiveness of prostate cancer screening: a systematic review of decision-analytical models.

BACKGROUND: There is ongoing debate about the harms and benefits of a national prostate cancer screening programme. Several model-based cost-effectiveness analyses have been developed to determine whether the benefits of prostate cancer screening outweigh the costs and harms caused by over-detection and over-treatment, and the different approaches may impact results. METHODS: To identify models of prostate cancer used to assess the cost-effectiveness of prostate cancer screening strategies, a systematic review of articles published since 2006 was conducted using the NHS Economic Evaluation Database, Medline, EMBASE and HTA databases. The NICE website, UK National Screening website, reference lists from relevant studies were also searched and experts contacted. Key model features, inputs, and cost-effectiveness recommendations were extracted. RESULTS: Ten studies were included. Four of the studies identified some screening strategies to be potentially cost-effective at a PSA threshold of 3.0 ng/ml, including single screen at 55 years, annual or two yearly screens starting at 55 years old, and delayed radical treatment. Prostate cancer screening was modelled using both individual and cohort level models. Model pathways to reflect cancer progression varied widely, Gleason grade was not always considered and clinical verification was rarely outlined. Where quality of life was considered, the methods used did not follow recommended practice and key issues of overdiagnosis and overtreatment were not addressed by all studies. CONCLUSION: The cost-effectiveness of prostate cancer screening is unclear. There was no consensus on the optimal model type or approach to model prostate cancer progression. Due to limited data availability, individual patient-level modelling is unlikely to increase the accuracy of cost-effectiveness results compared with cohort-level modelling, but is more suitable when assessing adaptive screening strategies. Modelling prostate cancer is challenging and the justification for the data used and the approach to modelling natural disease progression was lacking. Country-specific data are required and recommended methods used to incorporate quality of life. Influence of data inputs on cost-effectiveness results need to be comprehensively assessed and the model structure and assumptions verified by clinical experts.

Estimating the sensitivity of a prostate cancer screening programme for different PSA cut-off levels: A UK case study.

INTRODUCTION: Policy decisions about prostate cancer screening require data on the natural history of histological cancers and the resulting impact of screening. However, the gold standard procedure required to identify true positive histological cancer is a full autopsy of the gland which is not possible in screening studies, leading to verification bias. We aim to estimate the sensitivity of a prostate cancer screening round (PSA result to diagnosis) relative to histological cancer. METHODS: We developed a framework combining data on UK screened and non-screened prostate cancer populations originating from a single round of population-based PSA testing among UK men aged 50-69 years, prostate cancer incidence data, and needle biopsy data from the published literature. RESULTS: Sensitivity of a screening round was highest at age 65-69 years at 33% (95% CI: 30%-37%) and 24% (95% CI: 21%-28%) for PSA cut-off levels of 3 ng/ml and 4 ng/ml, respectively. Sensitivity was lowest at age 50-54 at 15% (95% CI: 12%-17%) and 9% (95% CI: 8%-11%) for PSA cut-off levels of 3 ng/ml and 4 ng/ml, respectively. In contrast, the clinical detection rate in the absence of mass screening, relative to histological cancer, varied between 0.2%-0.7% at age 50-54 and 1.2%-2.7% at age 65-69 from 1995 to 2012. CONCLUSIONS: The framework enabled the sensitivity of a prostate cancer screening round relative to histological cancer diagnosis to be estimated and provides a basis to determine the impact and cost-effectiveness of prostate cancer screening. The approach could be adapted to inform the sensitivity of other biomarkers, cancers and screening programmes.

Can commonly prescribed drugs be repurposed for the prevention or treatment of Alzheimer's and other neurodegenerative diseases? Protocol for an observational cohort study in the UK Clinical Practice Research Datalink.

INTRODUCTION: Current treatments for Alzheimer's and other neurodegenerative diseases have only limited effectiveness meaning that there is an urgent need for new medications that could influence disease incidence and progression. We will investigate the potential of a selection of commonly prescribed drugs, as a more efficient and cost-effective method of identifying new drugs for the prevention or treatment of Alzheimer's disease, non-Alzheimer's disease dementias, Parkinson's disease and amyotrophic lateral sclerosis. Our research will focus on drugs used for the treatment of hypertension, hypercholesterolaemia and type 2 diabetes, all of which have previously been identified as potentially cerebroprotective and have variable levels of preclinical evidence that suggest they may have beneficial effects for various aspects of dementia pathology. METHODS AND ANALYSIS: We will conduct a hypothesis testing observational cohort study using data from the Clinical Practice Research Datalink (CPRD). Our analysis will consider four statistical methods, which have different approaches for modelling confounding. These are multivariable adjusted Cox regression; propensity matched regression; instrumental variable analysis and marginal structural models. We will also use an intention-to-treat analysis, whereby we will define all exposures based on the first prescription observed in the database so that the target parameter is comparable to that estimated by a randomised controlled trial. ETHICS AND DISSEMINATION: This protocol has been approved by the CPRD's Independent Scientific Advisory Committee (ISAC). We will publish the results of the study as open-access peer-reviewed publications and disseminate findings through national and international conferences as are appropriate.

Validating the use of Hospital Episode Statistics data and comparison of costing methodologies for economic evaluation: an end-of-life case study from the Cluster randomised triAl of PSA testing for Prostate cancer (CAP).

OBJECTIVES: To evaluate the accuracy of routine data for costing inpatient resource use in a large clinical trial and to investigate costing methodologies. DESIGN: Final-year inpatient cost profiles were derived using (1) data extracted from medical records mapped to the National Health Service (NHS) reference costs via service codes and (2) Hospital Episode Statistics (HES) data using NHS reference costs. Trust finance departments were consulted to obtain costs for comparison purposes. SETTING: 7 UK secondary care centres. POPULATION: A subsample of 292 men identified as having died at least a year after being diagnosed with prostate cancer in Cluster randomised triAl of PSA testing for Prostate cancer (CAP), a long-running trial to evaluate the effectiveness and cost-effectiveness of prostate-specific antigen (PSA) testing. RESULTS: Both inpatient cost profiles showed a rise in costs in the months leading up to death, and were broadly similar. The difference in mean inpatient costs was £899, with HES data yielding ∼8% lower costs than medical record data (differences compatible with chance, p=0.3). Events were missing from both data sets. 11 men (3.8%) had events identified in HES that were all missing from medical record review, while 7 men (2.4%) had events identified in medical record review that were all missing from HES. The response from finance departments to requests for cost data was poor: only 3 of 7 departments returned adequate data sets within 6 months. CONCLUSIONS: Using HES routine data coupled with NHS reference costs resulted in mean annual inpatient costs that were very similar to those derived via medical record review; therefore, routinely available data can be used as the primary method of costing resource use in large clinical trials. Neither HES nor medical record review represent gold standards of data collection. Requesting cost data from finance departments is impractical for large clinical trials. TRIAL REGISTRATION NUMBER: ISRCTN92187251; Pre-results.

Validation of the Hospital Episode Statistics Outpatient Dataset in England.

OBJECTIVES: The Hospital Episode Statistics (HES) dataset is a source of administrative 'big data' with potential for costing purposes in economic evaluations alongside clinical trials. This study assesses the validity of coverage in the HES outpatient dataset. METHODS: Men who died of, or with, prostate cancer were selected from a prostate-cancer screening trial (CAP, Cluster randomised triAl of PSA testing for Prostate cancer). Details of visits that took place after 1/4/2003 to hospital outpatient departments for conditions related to prostate cancer were extracted from medical records (MR); these appointments were sought in the HES outpatient dataset based on date. The matching procedure was repeated for periods before and after 1/4/2008, when the HES outpatient dataset was accredited as a national statistic. RESULTS: 4922 outpatient appointments were extracted from MR for 370 men. 4088 appointments recorded in MR were identified in the HES outpatient dataset (83.1%; 95% confidence interval [CI] 82.0-84.1). For appointments occurring prior to 1/4/2008, 2195/2755 (79.7%; 95% CI 78.2-81.2) matches were observed, while 1893/2167 (87.4%; 95% CI 86.0-88.9) appointments occurring after 1/4/2008 were identified (p for difference <0.001). 215/370 men (58.1%) had at least one appointment in the MR review that was unmatched in HES, 155 men (41.9%) had all their appointments identified, and 20 men (5.4%) had no appointments identified in HES. CONCLUSIONS: The HES outpatient dataset appears reasonably valid for research, particularly following accreditation. The dataset may be a suitable alternative to collecting MR data from hospital notes within a trial, although caution should be exercised with data collected prior to accreditation.