Globally, cancer is a major health issue that imposes a heavy burden on society. Statistics from 2020 report there were more than 19 million people who were newly diagnosed with cancer and nearly 10 million people who died from cancer worldwide.1 Among all cancer types, breast, cervi-cal, colorectal, and lung cancers are the most common diagnoses in females, while lung, prostate, colorectal, and gastric cancers are the most common diagnoses in males.1 Deaths associated with these most common cancers constitute the vast majority of all cancer mortality, thus requiring attention and proactive efforts.
Cancer screening has been found to help identify precancerous conditions or early-stage cancers. This can subsequently increase the chance of curing the cancer and thereby reduce cancer mortality.2 Given the significant impact of cancer screening on reducing incidence of cancer and mortality from the disease, many countries have proposed guidelines and programs for cancer screening to improve uptake of cancer screening. The American Cancer Society consistently updates recommendations and guidance to promote health professionals’ and the general public's practice in screening for multiple types of cancer.3 Professional associations in Europe and the United Kingdom have also issued a series of recommendations and position statements on population-based screening of breast, cervical, and colorectal cancers.4 In Australia and New Zealand, national screening programs targeting several types of cancer, such as colorectal and cervical, have been implemented for decades.5,6 Asian countries such as China, Japan, South Korea, India, Thailand, and Indonesia have launched cancer screening guidelines and national programs to tackle the increasing incidence and mortality rates from cancer in the region.7,8
It should be noted that although the usefulness of cancer screening is evident in research settings, its actual impact in the real world is largely determined by public adherence.9,10 Studies have found that unfavorable health care models, insufficient physician-patient communication, poor shared decision-making, and low socioeconomic status are factors that affect adherence to cancer screening.11,12 To solve these problems, centralized and population-based screening programs with designated health professionals and financial coverage have been implemented. These have had a positive effect on improving cancer screening adherence.13,14 However, despite these efforts, public adherence to cancer screening as per recommendations is suboptimal. Some studies have reported that less than half of eligible individuals who were invited to participate in centralized14 or population-based15 cancer screening programs were able to complete all scheduled screening tests.
Recently, evidence-based reviews suggest that individuals’ adherence to cancer screening is significantly influenced by a series of cognitive, psychological, emotional, cultural, and social factors, such as fear of screening, feelings of embarrassment, sense of distrust, lack of perceived risk of cancer, or logistical issues16,17 This echoes insights in behavioral economics in which, rather than being completely determined by rational thinking, individuals’ decision-making and behaviors can be modulated by biased emotional, mental, and cognitive processing.18,19 Under this hypothetical mechanism, individuals may underrate potential but uncertain benefits in the future (eg, reduced incidence of and mortality from advanced cancer) by attaching too much importance to tangible costs in the present (eg, discomfort and inconvenience associated with cancer screening).18,19 Such decision biases could be addressed by offsetting immediate costs and/or providing immediate benefits.18,19
Informed by these perspectives of behavioral economics, researchers have designed multiple interventions to overcome individual decision biases and found promise in improving patient adherence. Specific behavioral economic interventions can include financial incentives, framing (ie, introducing certain options by emphasizing either their positive or negative aspects), choice architecture (ie, altering choice environment to systematically influence individuals’ decision-making, such as using a default option or including a more modest option to avoid the sense of extreme choice), reminders, feedback, and social influences.20
In recent years, numerous interventions involving behavioral economic principles have been tested to promote targeted populations’ adherence to cancer screening.21-26 For instance, given that people tend to perceive that cancer screening is time-consuming, costly, and uncomfortable with no tangible benefit in the short term, researchers used immediate and tangible incentives such as money or lottery-based awards to offset such present bias. However, the results of these studies have been inconsistent, with some concluding that financial incentives are not useful for promoting cancer screening,21,22 and others considering such incentives as an effective strategy when used appropriately.23,24 Another example is framing and reinforcing the benefits and meaning of cancer screening by using simple text message reminders, which has been found to increase the rates of cancer screening.25 In addition, addressing non-rational factors in decision-making could nudge individuals’ behavior. Research has shown that adding a decoy option of male practitioners into the appointment system can improve the intention and choice of endoscopic screening for colorectal cancer in women, who prefer to receive services from same-sex practitioners.26
The behavioral economic interventions mentioned above are brief and straightforward, and can be easily implemented in public health settings. However, the scattered findings cannot inform future research and practice without an evidence synthesis. Currently, no systematic review has elucidated the role of behavioral economic insights in promoting cancer screening. In order to identify whether interventions informed by behavioral economics can effectively improve cancer screening uptake and adherence, it is necessary to systematically analyze the existing evidence to guide future research and practice.
A preliminary search of PROSPERO, PubMed, Cochrane Database of Systematic Reviews, and JBI Evidence Synthesis was conducted on September 19, 2021, with results showing no similar systematic or scoping review on the topic, with the exception of ne registered protocol of an ongoing review on the use of behavioral economic interventions in promoting colorectal cancer screening.27 However, this protocol limited the inclusion criteria to randomized controlled trials published in the English language, making it a narrow range of accessible information for evidence synthesis. A broader scope will be adopted in this review, which will consider experimental, quasi-experimental, and analytical observational studies involving major adult cancers, including breast, lung, prostate, cervical, colorectal, and gastric cancers.
What is the effectiveness of behavioral economic interventions for improving uptake of and adherence to cancer screening?
This review will consider studies that include adults (aged ≥ 18 years) who are eligible for any type of cancer screening as per recommended guidelines.
This review will consider studies that examine interventions adopting behavioral economic principles that aim to address individuals’ decision bias pertaining to cancer screening use and adherence. The operational definition of “behavioral economic interventions” in this review refers to brief and straightforward interventions designed to address non-rational and non-conscious aspects of human thought to improve decisions. Such interventions include, but are not limited to, financial incentives, framing, choice architecture, reminders, feedback, and social influences.
This review will consider studies that compare interventions of interest to no intervention, usual care, or alternative interventions unrelated to behavioral economic insights.
This review will primarily focus on studies that report outcomes regarding the number/percentage of individuals who used cancer screening services as well as the number/percentage of individuals who completed cancer screening recommended by guidelines. The outcome data may be collected through either research-specific records or reviews of health records/registries. Participant self-reported intentions, choice, and satisfaction regarding the use of cancer screening services will also be included. Other indicators include detection rates of early-stage cancers, use of early intervention for cancer, and cancer-related mortality, which will be considered as secondary outcomes.
Types of studies
This review will consider experimental and quasi-experimental studies, including randomized controlled trials, cluster-randomized trials, pilot studies with a randomized controlled design, non-randomized controlled trials, and interrupted time series studies. Analytical observational studies including comparable cohort studies and case-control studies will also be considered.
This systematic review will be conducted according to the JBI methodology for systematic reviews of effectiveness.28 The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines29 will be followed in reporting the systematic review. The protocol for this systematic review has been registered with PROSPERO (CRD42021258370).
A limited initial search of PubMed was conducted to identify articles relevant to the topic. The titles, abstracts, and keywords of these articles were used to develop the full search strategy (see Appendix I), which will be adapted for all information sources. To ensure comprehensiveness and correctness, this systematic review will use the key search strings for behavioral economic interventions identical to the systematic review conducted by Roseleur et al.20 The reference lists of literature selected for methodological quality assessment will be manually searched to identify additional relevant studies. Literature will be searched from the inception dates of the databases until the present. No restrictions on language and date of publication or post will be set for the studies.
Five electronic databases, CINAHL (EBSCO), the Cochrane Library, PsycINFO (EBSCO), PubMed, and Web of Science, will be searched for published evidence. Google Scholar, OpenGrey, ProQuest, as well as the websites of government nudge units, international agencies, and academic societies will be searched for unpublished evidence and gray literature. Two trial registries, Cochrane Central Register of Controlled Trials (CENTRAL) and ClinicalTrials.gov, will be searched for registered ongoing or completed clinical trials.
After a comprehensive literature search, all records generated from the search will be imported into EndNote v.X9 (Clarivate Analytics, PA, USA). After removing the duplicates, two independent reviewers will screen the title, abstract, keywords, and full text of the remaining records against eligibility criteria to identify appropriate studies. Discussion among all members of the review team will be held during the study selection process, as necessary, to achieve consensus regarding the retention of eligible studies.
Assessment of methodological quality
The JBI critical appraisal checklists for experimental, quasi-experimental, and observational studies28 will be used to assess methodological quality of the studies included in the review. Two reviewers will perform the assessment independently, while a third reviewer will be invited to intervene if disagreements arise. All included studies will be used for data extraction and synthesis regardless of methodological quality. However, the issues regarding methodological quality of individual studies will be discussed and considered when drawing conclusions and making recommendations for clinical practice.
Two reviewers will perform data extraction independently using the standardized data extraction tool provided in JBI System for the Unified Management, Assessment and Review of Information (JBI SUMARI; JBI, Adelaide, Australia).28 Data to be extracted from the included studies will be first author, publication year and location, sample size, characteristics of participants (ie, age, gender, race, education, income, occupation, and types of cancer), study context and design, funding sources, contents and dosage of interventions, outcome measures, effect measures of continuous and/or dichotomous data (ie, odds ratios, hazard ratios, or mean difference), statistical significance, and other methodological quality indicators (eg, randomization, allocation concealment, blinding, completeness of report). Any discrepancies between the two reviewers will be resolved through discussion. When necessary, a third reviewer will be included to achieve consensus. Authors of articles to be included in the review will be contacted for additional information if important data are missing.
Statistical meta-analysis with the random effects model will be conducted using JBI SUMARI,28 where appropriate. Heterogeneity pertaining to meta-analysis results will be determined using χ2 and I2 tests. Effect sizes will be calculated as odds ratios for dichotomous outcome data or (standardized) mean differences for continuous outcome data, together with their relevant 95% confidence intervals.
To address possible methodological heterogeneity, subgroup analyses are planned as per the types of cancers and interventions. Statistical tests (χ2 and I2) examining heterogeneity will be performed to identify differences in subgroups. If high statistical heterogeneity is observed in meta-analysis, sensitivity analyses will also be conducted by removing individual studies one by one to check the potential influence of each study. When 10 or more studies are included in a meta-analysis, a funnel plot will be generated using RevMan v.5.3 (Copenhagen: The Nordic Cochrane Centre, Cochrane) to determine whether there is publication bias. Publication bias will be determined by funnel plot asymmetry using Egger's test30 (for meta-analysis of continuous outcome data) or Harbord's test31 (for meta-analysis of dichotomous outcome data). Where meta-analysis is not applicable, narrative synthesis will be conducted to present findings with figures and tables.
Assessing certainty in the findings
The certainty of evidence will be assessed by two reviewers independently according to the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach.32 A downgrade will be assigned if a risk of bias, imprecision, inconsistency, indirectness, and/or publication bias of the review results is identified. Any discrepancy between the two reviewers will be resolved through discussion or with a third reviewer. A Summary of Findings (SoF) will be generated by the reviewers using GRADEpro (McMaster University, ON, Canada) to present the assessment results and justifications. The SoF will consider the primary outcomes, including number/percentage of individuals who used cancer screening services; number/percentage of individuals who completed cancer screening recommended by guidelines; and participant self-reported intentions, choice, and satisfaction regarding the use of cancer screening services.
Authors MW and B-RM contributed equally in conceptualization and design of this protocol. All of the authors contributed to manuscript writing and finalization.
Appendix I: Search strategy
Search conducted on September 19, 2021
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