Colorectal cancer (CRC) is a major health problem worldwide. Although population-based CRC screening is strongly recommended in average-risk population, compliance rates are still far from the desirable rates. High levels of screening uptake are necessary for the success of any screening program. Therefore, the investigation of factors influencing participation is crucial prior to design and launches a population-based organized screening campaign. Several studies have identified screening behaviour factors related to potential participants, providers, or health care system. These influencing factors can also be classified in non-modifiable (i.e., demographic factors, education, health insurance, or income) and modifiable factors (i.e., knowledge about CRC and screening, patient and provider attitudes or structural barriers for screening). Modifiable determinants are of great interest as they are plausible targets for interventions. Interventions at different levels (patient, providers or health care system) have been tested across the studies with different results. This paper analyzes factors related to CRC screening behaviour and potential interventions designed to improve screening uptake.
Colorectal cancer (CRC) is the third leading cancer worldwide in terms of incidence accounting for 1.2 million new cases in 2008 (9.7% of total cancers) and the most common malignancy in developed regions (727.000 cases). CRC mortality rates rank fourth after lung, stomach, and liver cancer accounting for 608.000 deaths in 2008 and 8% of all cancer deaths [
The efficacy of CRC screening in terms of reduction of incidence and mortality rates has been shown in randomized controlled trials [
Screening uptake, defined as a cross-sectional assessment of compliance is a critical determinant of success for any population-based screening program. High rates of participation has been consistently associated with screening efficacy in terms of mortality reduction as well as cost-effectiveness [
Recently, a report from the European Commission considered a minimum uptake of 45% in average-risk population as an acceptable goal and 65% as a desirable rate [
Much attention has been given to investigate factors influencing CRC screening participation in average-risk population. A practical way to classify these factors is in non-modifiable factors (i.e., demographics, income, educational level, medical insurance, or family history) and modifiable factors, defined as those susceptible of intervention. Theories of health behaviour or theoretical models have been developed to understand why people do or do not practice different health behaviours, identifying modifiable factors which may be plausible targets of interventional strategies [
Mixed results have been reported regarding the influence of gender in screening participation. Although, overall, men look to participate more often than women in CRC screening, differences have been found depending on the country and screening strategy. In this way, a recent systematic review [
Several studies have addressed the association between age and screening uptake [
Disparities in screening uptake have been consistently reported in ethnic minorities across the studies [
A low socioeconomic status (income, unemployment, educational level, and residence) has been associated with lower screening participation in many studies [
Married people have been shown to be more compliant with healthier behaviour advise elsewhere [
Lifestyle and health factors have also been associated with screening uptake. For example, current smoking habit, which has been considered as an indicator of willingness to engage in preventive health behaviour, has been associated with poor CRC screening adherence, whereas screening rates increased in studies reporting participation in former smokers [
Inconsistent results have also been obtained regarding the effect of comorbidity on screening behavior, and, in consequence, it has been suggested that the effect of specific diseases should be studied separately [
Health care providers play a key role in the screening behaviour process by increasing awareness about CRC and screening tests in participants, reducing perceived barriers and increasing perceived benefits of screening tests. Physician recommendation has shown a strong correlation with CRC screening behaviours across the studies [
In a recent national representative survey of 1266 US physicians [
Health system factors have been associated with CRC screening uptake and physician recommendation [
Psychosocial factors involve those related to knowledge about CRC and screening, risk perception of CRC, and perceived barriers and benefits.
Knowledge about CRC and screening has been assessed in different ways across the studies [
The relative low public awareness about CRC in European studies contrast with data reported in US population. For example, an Irish study [
High-risk perception of developing CRC have been frequently associated with higher screening participation rates. For example, in one study carried out in a large representative sample of UK, participants who answered that their risk was higher than average-risk population were more willing to participate in CRC screening (98%) than those who answered same risk (84%) or lower risk (74%) [
Although different theoretical models have been developed in order to achieve a better understanding of health behaviour, all of them identify attitudes as important predictors of intention to screening and screening uptake. One of the most popular theoretical models is the Health Belief Model (HBM) [
More barriers have been detected in minority ethnic groups such as African Americans, Asian people, or Hispanics [
Interventions aimed at increasing CRC screening uptake can be classified into three categories: those that target patients, those that target providers, and those targeting health systems and communities.
The benefit of intervention targeting patients, defined as an increment in screening participation, has not always been demonstrated, probably because of the heterogeneity of the studies and several types of interventions used. Patient reminders consist of written or oral information (i.e., phone calls) reminding the necessity of undergoing screening to potential participants [
An association has been found between lack of knowledge about CRC and negative attitudes, unwillingness to participate in CRC screening, and finally screening behaviours [
Participant’s compliance is usually associated with provider’s motivation [
Incentive interventions try to motivate providers with direct or indirect rewards (usually economic incentives) to promote CRC screening in their patients. However, these studies are scarce in the literature and poorly effective [
Little evidence supports the efficacy of physician reminder-based interventions [
Improving the referral of patients for screening [
Underuse of population-based CRC screening is a multi-factorial problem involving patients, providers, and the organizational screening process. Plausible target factors for interventions aimed at increasing compliance have been identified at different levels. Specific interventions targeting these factors have been designed to increase screening uptake. However, they have had different success across the studies depending on the screening strategy and the intervention used. Despite the efforts, the impact on screening uptake has been low or moderate. A better knowledge on factors associated with screening compliance and development of more efficient interventions are warranted in order to achieve higher rates of CRC screening uptake.
This work was supported by a Grant from the Fundación Alfonso Martín Escudero (convocatoria 2010).