Worldwide each year, more than 940,000 new cases of colorectal cancer (CRC) are diagnosed and nearly 500,000 people die from the disease.1 CRC is the third most common cancer in both men and women worldwide, and the second most common cancer in the industrialized world.2
Early detection of CRC has been shown to improve outcomes through the detection of early-stage cancers and precursor lesions.3 Because early-stage disease frequently is asymptomatic, screening of the general population could decrease CRC incidence and mortality. There are 3 frequently used screening modalities: fecal occult blood test (FOBt), which reveals traces of blood in stool samples (an early sign of CRC); flexible sigmoidoscopy (FS), which involves visual inspection of the distal bowel for polyps and cancers; and total colonoscopy (TC), which visualizes the entire bowel and therefore is a more invasive examination.
Biennial screening using a guaiac FOBt (gFOBt) was found to decrease mortality by ∼15% after 13 years of follow-up in a large randomized trial in Funen, Denmark,4, 5 and by 13% after an 11-year follow-up in Nottingham, United Kingdom.6, 7 Neither study found a decrease in incidence, although follow-up continues. A more complex trial in Minnesota, USA, compared annual and biennial screening using FOBt.8 After an 18-year follow-up, mortality decreased by 33% in participants screened annually, and 21% in those screened biennially.9 Reductions in incidence of 20% and 17% were also observed for annually and biennially screened individuals, respectively.10
Four large-scale randomized clinical trials are evaluating FS as a screening tool. Baseline findings have been published showing that FS screening is safe (no major complications and relatively few perforations) and acceptable to the population.11–15 A randomized clinical trial of FS screening in Telemark, Norway reported an 80% reduction in CRC incidence rates with a 13-year follow-up. The numbers in this study were small, however.16
Although TC detects adenomas beyond the reach of FS no randomized clinical trials have been conducted. However, the U.S. National Polyp Study reported a reduction in the incidence of CRC when comparing those who had a complete colonoscopy where all adenomas were removed, to 3 reference groups: patients with polyps ≥1 cm who declined to undergo surgery; patients who had all rectal adenomas removed; and the final cohort was a sample of the general population.17
A country's screening initiatives need to be adapted to suit its population size, health care system and methods of funding. However, it will be beneficial to collect and share implementation and performance data among countries. Information on the effectiveness of technologies and methodologies can benefit existing programs. It can also provide insights and guidance to those in the planning stages of screening initiatives. Additionally, comparing the effectiveness of different screening modalities within a country could inform decision-making about an appropriate national screening protocol specific to the needs of that country. To facilitate the sharing of such information and comparisons, it is important to have a common nomenclature and for initiatives to be collecting the appropriate data. However, because colorectal screening is in its infancy in most countries, a common language to describe the screening process and common measures by which quality can be examined for all tests and types of programs have yet to be established.
In June 2002, the International Union Against Cancer and the American Cancer Society sponsored an international workshop in Oslo, Norway, on facilitating screening for CRC.18 From this meeting it was clear that a great deal of CRC screening activity was taking place worldwide, and that it would be beneficial to describe the activity and build a network to share experience and knowledge. Subsequently, the Centers for Disease Control and Prevention and the American Cancer Society supported a collaborative effort with Cancer Research UK to develop the International Colorectal Cancer Screening Network (ICRCSN).
The first aim of the ICRCSN was to identify and document the status of organized screening initiatives, and that information is reported in the present article. As a next step, the ICRCSN is focused on establishing a consensus minimum set of screening program descriptors and quality assurance measures with common definitions and measurement metrics to enable program evaluation and comparisons.