Colorectal Cancer Screening: Overview of Existing Programs
Colorectal Cancer Screening: Overview of Existing Programs
An organised screening programme involves a systematic process of inviting a target population to participate in screening and ensuring follow-up of those with a positive screen. An organised programme should measure and report on the quality of each step in the screening process. The IARC outlines the following elements for organised screening programmes:
In organised screening, substantial information technology infrastructure is required to support the programme including systems for invitations, recalls, reminders, tracking of screening results, ensuring follow-up and tracking of clinical outcomes such as cancer incidence, mortality and stage. For tracking of screening results, a set of universally applicable CRC screening measures and indicators have been established. A cancer registry is critical and can be linked to all other relevant databases including laboratories and endoscopic centres. In contrast, opportunistic screening is delivered outside of an organised screening programme on an ad hoc basis usually through fee-for-service reimbursement of physicians. Since organised screening focuses on quality assurance, it provides greater protection against the possible harms of screening including overscreening and underscreening, poor quality, inappropriate use of resources, complications arising from screening and poor follow-up of those with a positive screen.
The approach to screening in the USA is largely opportunistic. The contributions and quality initiatives from many national bodies has been crucial, including the US Preventive Services Task Force (USPSTF), an independent volunteer panel of national experts in prevention and evidence-based medicine that reviews evidence and makes recommendations to guide the choice of CRC screening tests. In addition, multiple professional associations have emphasised the importance of colonoscopy quality in the context of CRC screening. Equity of access to screening in the USA remains uncertain, however.
In 2010, the IARC published the European Guidelines for Quality Assurance in Colorectal Cancer Screening and Diagnosis. These guidelines outline targets for key performance indicators for CRC screening including participation, follow-up and cancer detection rates. For example, the guidelines recommend that invitation coverage in the target population should be high (95%) and that programmes should aim for participation rates of at least 65%.
Given that at least 10 years are required to plan, pilot and implement a screening programme, the full impact of a nationwide screening programme on indicators such as CRC mortality rates requires long follow-up. Therefore, an intermediate measure may be used to evaluate programme performance, expressed as the number of persons with advanced neoplasia detected per 1000 invited individuals during the screening interval. This measure takes multiple factors into consideration namely participation rate, positivity rate and the positive predictive value for the detection of advanced neoplasia. It is thus a balanced assessment of the overall performance of a screening programme. Table 2 outlines the number of people with advanced neoplasia identified per 1000 invited individuals in those programmes that have published their results. There is marked variation across screening tests and within a screening test type for all indicators. Wide ranges for the gFOBT/FIT-based results may be due to the use of more sensitive tests or more stringent criteria for defining test positivity.
Cost-effectiveness studies for CRC screening have concluded that screening is cost-effective compared with no screening. Microsimulation models can help to identify the most appropriate screening strategy given the available resources and budget constraints. The efficiency frontier will identify strategies that are the most effective in terms of life-years gained relative to the cost of the screening strategy.
Cost-effectiveness studies have shown that screening can also be cost-effective in countries with limited financial resources. However, access to and improvement in CRC treatment may be a higher priority than screening in these settings. Using resources to implement population-based screening in a region with no or very limited access to treatment would not be a cost-effective measure.
Organised and Opportunistic Screening
An organised screening programme involves a systematic process of inviting a target population to participate in screening and ensuring follow-up of those with a positive screen. An organised programme should measure and report on the quality of each step in the screening process. The IARC outlines the following elements for organised screening programmes:
An explicit policy with specified age categories, screening method and screening interval
A defined target population
A management team responsible for implementation
A healthcare team for decisions, care and follow-up of patients with positive screening tests
A quality assurance structure for every step in the process
A process for monitoring, evaluating and identifying cancer occurrence in the population.
In organised screening, substantial information technology infrastructure is required to support the programme including systems for invitations, recalls, reminders, tracking of screening results, ensuring follow-up and tracking of clinical outcomes such as cancer incidence, mortality and stage. For tracking of screening results, a set of universally applicable CRC screening measures and indicators have been established. A cancer registry is critical and can be linked to all other relevant databases including laboratories and endoscopic centres. In contrast, opportunistic screening is delivered outside of an organised screening programme on an ad hoc basis usually through fee-for-service reimbursement of physicians. Since organised screening focuses on quality assurance, it provides greater protection against the possible harms of screening including overscreening and underscreening, poor quality, inappropriate use of resources, complications arising from screening and poor follow-up of those with a positive screen.
The approach to screening in the USA is largely opportunistic. The contributions and quality initiatives from many national bodies has been crucial, including the US Preventive Services Task Force (USPSTF), an independent volunteer panel of national experts in prevention and evidence-based medicine that reviews evidence and makes recommendations to guide the choice of CRC screening tests. In addition, multiple professional associations have emphasised the importance of colonoscopy quality in the context of CRC screening. Equity of access to screening in the USA remains uncertain, however.
Quality Assurance
In 2010, the IARC published the European Guidelines for Quality Assurance in Colorectal Cancer Screening and Diagnosis. These guidelines outline targets for key performance indicators for CRC screening including participation, follow-up and cancer detection rates. For example, the guidelines recommend that invitation coverage in the target population should be high (95%) and that programmes should aim for participation rates of at least 65%.
Given that at least 10 years are required to plan, pilot and implement a screening programme, the full impact of a nationwide screening programme on indicators such as CRC mortality rates requires long follow-up. Therefore, an intermediate measure may be used to evaluate programme performance, expressed as the number of persons with advanced neoplasia detected per 1000 invited individuals during the screening interval. This measure takes multiple factors into consideration namely participation rate, positivity rate and the positive predictive value for the detection of advanced neoplasia. It is thus a balanced assessment of the overall performance of a screening programme. Table 2 outlines the number of people with advanced neoplasia identified per 1000 invited individuals in those programmes that have published their results. There is marked variation across screening tests and within a screening test type for all indicators. Wide ranges for the gFOBT/FIT-based results may be due to the use of more sensitive tests or more stringent criteria for defining test positivity.
Cost-effectiveness
Cost-effectiveness studies for CRC screening have concluded that screening is cost-effective compared with no screening. Microsimulation models can help to identify the most appropriate screening strategy given the available resources and budget constraints. The efficiency frontier will identify strategies that are the most effective in terms of life-years gained relative to the cost of the screening strategy.
Cost-effectiveness studies have shown that screening can also be cost-effective in countries with limited financial resources. However, access to and improvement in CRC treatment may be a higher priority than screening in these settings. Using resources to implement population-based screening in a region with no or very limited access to treatment would not be a cost-effective measure.