A Model-Based Comparison of Breast Cancer Screening Strategies: Mammograms and Clinical Breast Examinations

Incorporating Baseline Breast Density When Screening Women at Average Risk for Breast Cancer : A Cost-Effectiveness Analysis

BACKGROUND

Breast density classification is largely determined by mammography, making the timing of the first screening mammogram clinically important.

OBJECTIVE

To evaluate the cost-effectiveness of breast cancer screening strategies that are stratified by breast density.

DESIGN

Microsimulation model to generate the natural history of breast cancer for women with and those without dense breasts and assessment of the cost-effectiveness of strategies tailored to breast density and nontailored strategies.

DATA SOURCES

Model parameters from the literature; statistical modeling; and analysis of Surveillance, Epidemiology, and End Results-Medicare data.

TARGET POPULATION

Women aged 40 years or older.

TIME HORIZON

Lifetime.

PERSPECTIVE

Societal.

INTERVENTION

No screening; biennial or triennial mammography from age 50 to 75 years; annual mammography from age 50 to 75 years for women with dense breasts at age 50 years and biennial or triennial mammography from age 50 to 75 years for those without dense breasts at age 50 years; and annual mammography at age 40 to 75 years for women with dense breasts at age 40 years and biennial or triennial mammography at age 50 to 75 years for those without dense breasts at age 40 years.

OUTCOME MEASURES

Lifetime costs and quality-adjusted life-years (QALYs), discounted at 3% annually.

RESULTS OF BASE-CASE ANALYSIS

Baseline screening at age 40 years followed by annual screening at age 40 to 75 years for women with dense breasts and biennial screening at age 50 to 75 years for women without dense breasts was effective and cost-effective, yielding an incremental cost-effectiveness ratio of $36 200 per QALY versus the biennial strategy at age 50 to 75 years.

RESULTS OF SENSITIVITY ANALYSIS

At a societal willingness-to-pay threshold of $100 000 per QALY, the probability that the density-stratified strategy at age 40 years was optimal was 56% compared with 6 other strategies.

LIMITATION

Findings may not be generalizable outside the United States.

CONCLUSION

The study findings advocate for breast density-stratified screening with baseline mammography at age 40 years.

PRIMARY FUNDING SOURCE

National Cancer Institute.

Cost-Effectiveness of Cancer Screening: Health and Costs in Life Years Gained

INTRODUCTION

Studies reporting on the cost-effectiveness of cancer screening usually account for quality of life losses and healthcare costs owing to cancer but do not account for future costs and quality of life losses related to competing risks. This study aims to demonstrate the impact of medical costs and quality of life losses of other diseases in the life years gained on the cost-effectiveness of U.S. cancer screening.

METHODS

Cost-effectiveness studies of breast, cervical, and colorectal cancer screening in the U.S. were identified using a systematic literature review. Incremental cost-effectiveness ratios of the eligible articles were updated by adding lifetime expenditures and health losses per quality-adjusted life year gained because of competing risks. This was accomplished using data on medical spending and quality of life by age and disease from the Medical Expenditure Panel Survey (2011-2015) combined with cause-deleted life tables. The study was conducted in 2018.

RESULTS

The impact of quality of life losses and healthcare expenditures of competing risks in life years gained incurred owing to screening were the highest for breast cancer and the lowest for cervical cancer. The updates suggest that incremental cost-effectiveness ratios are underestimated by $10,300-$13,700 per quality-adjusted life year gained if quality of life losses and healthcare expenditures of competing risks are omitted in economic evaluations. Furthermore, cancer screening programs that were considered cost saving, were found not to be so following the inclusion of medical expenditures of competing risks.

CONCLUSIONS

Practical difficulties in quantifying quality of life losses and healthcare expenditures owing to competing risks in life years gained can be overcome. Their inclusion can have a substantial impact on the cost-effectiveness of cancer screening programs.

Assessing the Cost-Effectiveness of Updated Breast Cancer Screening Guidelines for Average-Risk Women

BACKGROUND

Several specialty societies have recently updated their breast cancer screening guidelines in late 2015/early 2016.

OBJECTIVES

To evaluate the cost-effectiveness of US-based mammography screening guidelines.

METHODS

We developed a microsimulation model to generate the natural history of invasive breast cancer and capture how screening and treatment modified the natural course of the disease. We used the model to assess the cost-effectiveness of screening strategies, including annual screening starting at the age of 40 years, biennial screening starting at the age of 50 years, and a hybrid strategy that begins screening at the age of 45 years and transitions to biennial screening at the age of 55 years, combined with three cessation ages: 75 years, 80 years, and no upper age limit. Findings were summarized as incremental cost-effectiveness ratio (cost per quality-adjusted life-year [QALY]) and cost-effectiveness acceptability frontier.

RESULTS

The screening strategy that starts annual mammography at the age of 45 years and switches to biennial screening between the ages of 55 and 75 years was the most cost-effective, yielding an incremental cost-effectiveness ratio of $40,135/QALY. Probabilistic analysis showed that the hybrid strategy had the highest probability of being optimal when the societal willingness to pay was between $44,000/QALY and $103,500/QALY. Within the range of commonly accepted societal willingness to pay, no optimal strategy involved screening with a cessation age of 80 years or older.

CONCLUSIONS

The screening strategy built on a hybrid design is the most cost-effective for average-risk women. By considering the balance between benefits and harms in forming its recommendations, this hybrid screening strategy has the potential to optimize the health care system's investment in the early detection and treatment of breast cancer.

Improvement in risk prediction, early detection and prevention of breast cancer in the NHS Breast Screening Programme and family history clinics: a dual cohort study

Background

In the UK, women are invited for 3-yearly mammography screening, through the NHS Breast Screening Programme (NHSBSP), from the ages of 47–50 years to the ages of 69–73 years. Women with family histories of breast cancer can, from the age of 40 years, obtain enhanced surveillance and, in exceptionally high-risk cases, magnetic resonance imaging. However, no NHSBSP risk assessment is undertaken. Risk prediction models are able to categorise women by risk using known risk factors, although accurate individual risk prediction remains elusive. The identification of mammographic breast density (MD) and common genetic risk variants [single nucleotide polymorphisms (SNPs)] has presaged the improved precision of risk models.

Objectives

To (1) identify the best performing model to assess breast cancer risk in family history clinic (FHC) and population settings; (2) use information from MD/SNPs to improve risk prediction; (3) assess the acceptability and feasibility of offering risk assessment in the NHSBSP; and (4) identify the incremental costs and benefits of risk stratified screening in a preliminary cost-effectiveness analysis.

Design

Two cohort studies assessing breast cancer incidence.

Setting

High-risk FHC and the NHSBSP Greater Manchester, UK.

Participants

A total of 10,000 women aged 20–79 years [Family History Risk Study (FH-Risk); UK Clinical Research Network identification number (UKCRN-ID) 8611] and 53,000 women from the NHSBSP [aged 46–73 years; Predicting the Risk of Cancer At Screening (PROCAS) study; UKCRN-ID 8080].

Interventions

Questionnaires collected standard risk information, and mammograms were assessed for breast density by a number of techniques. All FH-Risk and 10,000 PROCAS participants participated in deoxyribonucleic acid (DNA) studies. The risk prediction models Manual method, Tyrer–Cuzick (TC), BOADICEA (Breast and Ovarian Analysis of Disease Incidence and Carrier Estimation Algorithm) and Gail were used to assess risk, with modelling based on MD and SNPs. A preliminary model-based cost-effectiveness analysis of risk stratified screening was conducted.

Main outcome measures

Breast cancer incidence.

Data sources

The NHSBSP; cancer registration.

Results

A total of 446 women developed incident breast cancers in FH-Risk in 97,958 years of follow-up. All risk models accurately stratified women into risk categories. TC had better risk precision than Gail, and BOADICEA accurately predicted risk in the 6268 single probands. The Manual model was also accurate in the whole cohort. In PROCAS, TC had better risk precision than Gail [area under the curve (AUC) 0.58 vs. 0.54], identifying 547 prospective breast cancers. The addition of SNPs in the FH-Risk case–control study improved risk precision but was not useful inBRCA1(breast cancer 1 gene) families. Risk modelling of SNPs in PROCAS showed an incremental improvement from using SNP18 used in PROCAS to SNP67. MD measured by visual assessment score provided better risk stratification than automatic measures, despite wide intra- and inter-reader variability. Using a MD-adjusted TC model in PROCAS improved risk stratification (AUC = 0.6) and identified significantly higher rates (4.7 per 10,000 vs. 1.3 per 10,000;p < 0.001) of high-stage cancers in women with above-average breast cancer risks. It is not possible to provide estimates of the incremental costs and benefits of risk stratified screening because of lack of data inputs for key parameters in the model-based cost-effectiveness analysis.

Conclusions

Risk precision can be improved by using DNA and MD, and can potentially be used to stratify NHSBSP screening. It may also identify those at greater risk of high-stage cancers for enhanced screening. The cost-effectiveness of risk stratified screening is currently associated with extensive uncertainty. Additional research is needed to identify data needed for key inputs into model-based cost-effectiveness analyses to identify the impact on health-care resource use and patient benefits.

Future work

A pilot of real-time NHSBSP risk prediction to identify women for chemoprevention and enhanced screening is required.

Funding

The National Institute for Health Research Programme Grants for Applied Research programme. The DNA saliva collection for SNP analysis for PROCAS was funded by the Genesis Breast Cancer Prevention Appeal.

Simulation models in population breast cancer screening: A systematic review

The aim of this review was to critically evaluate published simulation models for breast cancer screening of the general population and provide a direction for future modeling. A systematic literature search was performed to identify simulation models with more than one application. A framework for qualitative assessment which incorporated model type; input parameters; modeling approach, transparency of input data sources/assumptions, sensitivity analyses and risk of bias; validation, and outcomes was developed. Predicted mortality reduction (MR) and cost-effectiveness (CE) were compared to estimates from meta-analyses of randomized control trials (RCTs) and acceptability thresholds. Seven original simulation models were distinguished, all sharing common input parameters. The modeling approach was based on tumor progression (except one model) with internal and cross validation of the resulting models, but without any external validation. Differences in lead times for invasive or non-invasive tumors, and the option for cancers not to progress were not explicitly modeled. The models tended to overestimate the MR (11-24%) due to screening as compared to optimal RCTs 10% (95% CI - 2-21%) MR. Only recently, potential harms due to regular breast cancer screening were reported. Most scenarios resulted in acceptable cost-effectiveness estimates given current thresholds. The selected models have been repeatedly applied in various settings to inform decision making and the critical analysis revealed high risk of bias in their outcomes. Given the importance of the models, there is a need for externally validated models which use systematical evidence for input data to allow for more critical evaluation of breast cancer screening.

Cost-effectiveness of alternative strategies for integrating MRI into breast cancer screening for women at high risk

BACKGROUND

Magnetic resonance imaging (MRI) is recommended for women at high risk for breast cancer. We evaluated the cost-effectiveness of alternative screening strategies involving MRI.

METHODS

Using a microsimulation model, we generated life histories under different risk profiles, and assessed the impact of screening on quality-adjusted life-years, and lifetime costs, both discounted at 3%. We compared 12 screening strategies combining annual or biennial MRI with mammography and clinical breast examination (CBE) in intervals of 0.5, 1, or 2 years vs without, and reported incremental cost-effectiveness ratios (ICERs).

RESULTS

Based on an ICER threshold of $100,000/QALY, the most cost-effective strategy for women at 25% lifetime risk was to stagger MRI and mammography plus CBE every year from age 30 to 74, yielding ICER $58,400 (compared to biennial MRI alone). At 50% lifetime risk and with 70% reduction in MRI cost, the recommended strategy was to stagger MRI and mammography plus CBE every 6 months (ICER=$84,400). At 75% lifetime risk, the recommended strategy is biennial MRI combined with mammography plus CBE every 6 months (ICER=$62,800).

CONCLUSIONS

The high costs of MRI and its lower specificity are limiting factors for annual screening schedule of MRI, except for women at sufficiently high risk.

Melanoma death prevention: moving away from the sun

This evidence-backed editorial addresses the limitations of solely primary prevention campaigns and outlines the proven efficacy of early detection/secondary prevention strategies with respect to melanoma. It synthesizes experience from several outreach efforts that have resulted in sustained improvements in knowledge and self-skin examination behaviors. Data demonstrate that educational campaigns emphasizing increased knowledge about melanoma and self-screening practices correlate with thinner tumors. The editorial also confronts the lack of data around skin cancer screening per the US Preventative Services Task Force. It explains how we might address the issue to obtain solid evidence to back a recommendation for screening of high-risk populations in the future. Cost-efficacy of skin cancer screening is also addressed. Lastly, lessons learned from other cancers, particularly breast cancer, with respect to successful educational campaign creation and development of an effective cause marketing campaign for advocacy are discussed. Hypothetical ideas for a screening algorithm and for educational/media campaigns are presented with the hope of triggering thoughtful discussion and forward momentum.

Risk-specific optimal cancer screening schedules: an application to breast cancer early detection

The optimal schedules for breast cancer screening in terms of examination frequency and ages at examination are of practical interest. A decision-theoretic approach is explored to search for optimal cancer screening programs which should achieve maximum survival benefit while balancing the associated cost to the health care system. We propose a class of utility functions that account for costs associated with screening examinations and value of survival benefit under a non-stable disease model. We consider two different optimization criteria: optimize the number of screening examinations with equal screening intervals between exams but without a pre-fixed total cost; and optimize the ages at which screening should be given for a fixed total cost. We show that an optimal solution exists under each of the two frameworks. The proposed methods may consider women at different levels of risk for breast cancer so that the optimal screening strategies will be tailored according to a woman's risk of developing the disease. Results of a numerical study are presented and the proposed models are illustrated with various data inputs. We also use the data inputs from the Health Insurance Plan of New York (HIP) and Canadian National Breast Screening Study (CNBSS) to illustrate the proposed models and to compare the utility values between the optimal schedules and the actual schedules in the HIP and CNBSS trials. Here, the utility is defined as the difference in cure rates between cases found at screening examinations and cases found between screening examinations while accounting for the cost of examinations, under a given screening schedule.

Cost-effectiveness of clinical breast assessment-based screening in rural Egypt

INTRODUCTION

Breast cancer is the most common cancer in Egyptian women. However, the mean tumor size at diagnosis is 4.5 cm, and the median age is approximately 46 years. Both of these factors decrease the utility and cost-effectiveness of a mammography-based screening program typically designed for developed countries. We report the first clinical breast assessment-based screening project in an entirely rural Egyptian community.

METHODS

Targeted population: Women aged 25-65 years in three municipal regions of Dakahlia province, Egypt. The estimated targeted population was 57,500 and participation was voluntary. First stage was performed at primary health care points. Surgeons performed systematic clinical breast examination. All data were collected at Mansoura University. Abnormal findings in the primary examination led to an invitation to the Oncology Center--Mansoura University--where the second stage of the study took place. It comprised repeat examination, ultrasonography, and/or mammography. Therapeutic interventions were performed at the governmentally funded Mansoura Oncology Center.

RESULTS

Voluntary participation reached 10.2% of the target group and abnormal clinical examination represented 3.2% (191/5,900). The screen-detected cancers were (18/5,900) of examined population, and thus the cancer detection rate of clinical breast assessment-based screening was 30.5 per 100,000 of participating women during 2 years. The tumor size was 1.5 cm (median) and 1.3 cm (mean). The cost of screening per cancer case detected was approximately 415 US$, and the overall cost of treating a screen-detected cancer was 1,015-1,215 US$.

CONCLUSIONS

Clinical breast assessment-based screening with selective mammography is an effective modality, which improves the results of breast cancer management in Egypt.

Bayesian Calibration of Microsimulation Models

Microsimulation models that describe disease processes synthesize information from multiple sources and can be used to estimate the effects of screening and treatment on cancer incidence and mortality at a population level. These models are characterized by simulation of individual event histories for an idealized population of interest. Microsimulation models are complex and invariably include parameters that are not well informed by existing data. Therefore, a key component of model development is the choice of parameter values. Microsimulation model parameter values are selected to reproduce expected or known results though the process of model calibration. Calibration may be done by perturbing model parameters one at a time or by using a search algorithm. As an alternative, we propose a Bayesian method to calibrate microsimulation models that uses Markov chain Monte Carlo. We show that this approach converges to the target distribution and use a simulation study to demonstrate its finite-sample performance. Although computationally intensive, this approach has several advantages over previously proposed methods, including the use of statistical criteria to select parameter values, simultaneous calibration of multiple parameters to multiple data sources, incorporation of information via prior distributions, description of parameter identifiability, and the ability to obtain interval estimates of model parameters. We develop a microsimulation model for colorectal cancer and use our proposed method to calibrate model parameters. The microsimulation model provides a good fit to the calibration data. We find evidence that some parameters are identified primarily through prior distributions. Our results underscore the need to incorporate multiple sources of variability (i.e., due to calibration data, unknown parameters, and estimated parameters and predicted values) when calibrating and applying microsimulation models.

Cost-effectiveness analysis of mammography and clinical breast examination strategies: a comparison with current guidelines

PURPOSE

Breast cancer screening by mammography and clinical breast exam are commonly used for early tumor detection. Previous cost-effectiveness studies considered mammography alone or did not account for all relevant costs. In this study, we assessed the cost-effectiveness of screening schedules recommended by three major cancer organizations and compared them with alternative strategies. We considered costs of screening examinations, subsequent work-up, biopsy, and treatment interventions after diagnosis.

METHODS

We used a microsimulation model to generate women's life histories, and assessed screening and treatment effects on survival. Using statistical models, we accounted for age-specific incidence, preclinical disease duration, and age-specific sensitivity and specificity for each screening modality. The outcomes of interest were quality-adjusted life years (QALY) saved and total costs with a 3% annual discount rate. Incremental cost-effectiveness ratios were used to compare strategies. Sensitivity analyses were done by varying some of the assumptions.

RESULTS

Compared with guidelines from the National Cancer Institute and the U.S. Preventive Services Task Force, alternative strategies were more efficient. Mammography and clinical breast exam in alternating years from ages 40 to 79 years was a cost-effective alternative compared with the guidelines, costing $35,500 per QALY saved compared with no screening. The American Cancer Society guideline was the most effective and the most expensive, costing over $680,000 for an added QALY compared with the above alternative.

CONCLUSION

Screening strategies with lower costs and benefits comparable with those currently recommended should be considered for implementation in practice and for future guidelines.

Reducing the effects of lead-time bias, length bias and over-detection in evaluating screening mammography: a censored bivariate data approach

Measuring the benefit of screening mammography is difficult due to lead-time bias, length bias and over-detection. We evaluated the benefit of screening mammography in reducing breast cancer mortality using observational data from the SEER-Medicare linked database. The conceptual model divided the disease duration into two phases: preclinical (T(0)) and symptomatic (T(1)) breast cancer. Censored information for the bivariate response vector ( T(0), T(1)) was observed and used to generate a likelihood function. However, the contribution to the likelihood function for some observations could not be calculated analytically, thus, censoring boundaries for these observations were modified. Inferences about the impact of screening mammography on breast cancer mortality were made based on maximum likelihood estimates derived from this likelihood function. Hazard ratios (95% confidence intervals) of 0.54 (0.48-0.61) and 0.33 (0.26- 0.42) for single and regular users (vs. non-users), respectively, demonstrated a protective effect of screening mammography among women 69 years and older. This method reduced the impact of lead-time bias, length bias and over-detection, which biased the estimated hazard ratios derived from standard survival models in favour of screening.

[Inequalities in clinical breast examination in São Leopoldo, Rio Grande do Sul, Brazil]

This cross-sectional population-based survey focused on the coverage of clinical breast examination (CBE) in women 20 to 60 years of age in São Leopoldo, Rio Grande do Sul State, Brazil, and described the factors associated with lack of CBE. The outcome was defined as having received a CBE by a physician during the year prior to the interview. Two different multivariate models were analyzed. Among the 1,026 women included in the sample, 556 (54.2%; 95%CI: 51.1-57.2) had received CBEs. Multivariate analysis including the entire sample of women showed that low socioeconomic status (SES) was the only variable associated with not having a CBE. In the other multivariate model (only women who had consulted physicians in the previous year, with or without CBE), a statistically significant effect was found for both SES and skin color. Thus, low SES was significantly associated with lack of CBE in both models. However, in the model limited to women with physician consultations in the previous year, skin color was the main factor for receiving CBE, suggesting that once differences in initial access to the health service were overcome, white women had a higher probability of receiving a clinical breast examination as part of their consultation.

Cost-effectiveness of bladder cancer screening

Bladder cancer is the fourth most common cancer in men and 25% of patients present with advanced disease resulting in a poor prognosis. Urine-based tests, including evaluation for blood in the urine or tumor markers, may allow early detection of cancer with resultant improved survival. Studies need to be performed to evaluate the feasibility and cost-effectiveness of screening high-risk populations such as smokers.

Cost-effectiveness analysis of screening modalities for breast cancer in Japan with special reference to women aged 40-49 years

Although the introduction of screening mammography in Japan would be expected to reduce mortality from breast cancer, the optimal screening modality in terms of cost-effectiveness remains unclear. We compared the cost-effectiveness ratio, defined as the cost required for a life-year saved, among the following three strategies: (1) annual clinical breast examination; (2) annual clinical breast examination combined with mammography; and (3) biennial clinical breast examination combined with mammography for women aged 30-79 years using a hypothetical cohort of 100 000. The sensitivity, specificity and early breast cancer rates were derived from studies conducted from 1995 to 2000 in Miyagi Prefecture. The treatment costs were based on a questionnaire survey conducted at 13 institutions in Japan. We used updated parameters that were needed in the analysis. Although the effectiveness of treatment in terms of the number of expected survival years was highest for annual combined modality, biennial combined modality had a higher cost-effectiveness ratio, followed by annual combined modality and annual clinical breast examination in all age groups. In women aged 40-49 years, annual combined modality saved 852.9 lives and the cost/survival duration was 3 394 300 yen/year, whereas for biennial combined modality the corresponding figures were 833.8 and 2 025 100 yen/year, respectively. Annual clinical breast examination did not confer any advantages in terms of effectiveness (815.5 lives saved) or cost-effectiveness (3 669 900 yen/year). While the annual combined modality was the most effective with respect to life-years saved among women aged 40-49 years, biennial combined modality was found to provide the highest cost-effectiveness.

Should we screen for bladder cancer in a high-risk population?: A cost per life-year saved analysis

BACKGROUND

The U.S. Food and Drug Administration recently approved screening high-risk patients for bladder cancer using urine-based markers. The cost and life-years saved associated with bladder cancer screening were evaluated.

METHODS

A Markov model was created to estimate cumulative cancer-related costs and efficacy of screening (vs. no screening) of a high-risk population for bladder cancer using a urine-based tumor marker over a 5-year period. Assumptions were based on literature review of survival and progression rates for patients with bladder cancer and costs associated with different bladder cancer disease states.

RESULTS

Screening for bladder cancer in a population with a 4% incidence of bladder cancer resulted in a gain of 3.0 life years per 1000 subjects at a cost savings of $101,000 for the population, assuming a 50% downstaging in the screened population from muscle-invasive to nonmuscle-invasive disease. One-way sensitivity analyses found that screening is the most cost-effective strategy if cancer incidence is >1.6%, tumor marker costs <$126, marker sensitivity is >26%, marker specificity is >54%, downstaging with screening is >20%, and office cystoscopy costs <$694. Varying costs of cystectomy, transurethral resection of bladder tumor (TURBT), chemotherapy, end-of-life care, costs of metastatic disease, and a computed tomography scan over a wide range did not affect the superiority of screening.

CONCLUSIONS

The model found that urine-based markers are cost-effective in a high-risk population. Prospective randomized trials in a completely asymptomatic high-risk cohort are indicated before bladder cancer screening can be recommended.

Evaluating markers for the early detection of cancer: overview of study designs and methods

BACKGROUND

The field of cancer biomarker development has been evolving rapidly. New developments both in the biologic and statistical realms are providing increasing opportunities for evaluation of markers for both early detection and diagnosis of cancer.

PURPOSE

To review the major conceptual and methodological issues in cancer biomarker evaluation, with an emphasis on recent developments in statistical methods together with practical recommendations.

METHODS

We organized this review by type of study: preliminary performance, retrospective performance, prospective performance and cancer screening evaluation.

RESULTS

For each type of study, we discuss methodologic issues, provide examples and discuss strengths and limitations.

CONCLUSION

Preliminary performance studies are useful for quickly winnowing down the number of candidate markers; however their results may not apply to the ultimate target population, asymptomatic subjects. If stored specimens from cohort studies with clinical cancer endpoints are available, retrospective studies provide a quick and valid way to evaluate performance of the markers or changes in the markers prior to the onset of clinical symptoms. Prospective studies have a restricted role because they require large sample sizes, and, if the endpoint is cancer on biopsy, there may be bias due to overdiagnosis. Cancer screening studies require very large sample sizes and long follow-up, but are necessary for evaluating the marker as a trigger of early intervention.