Colorectal cancer (CRC) is the third most common tumour in men and the second in women, accounting for 10% of all tumour types worldwide. Incidence is higher in males (ratio: 1.4) and for both genders there is a 10-fold difference in incidence between several regions. With 608 000 deaths estimated each year (∼8% of all cancer deaths), CRC is the fourth most common cancer-related cause of death in the world [1].
As a general observation, there has been an increasing incidence in countries where the overall risk of large bowel cancer was low, while in historically high-risk countries either a stabilisation (Western Europe and Australia) or a decrease (USA, Canada and New Zealand) in incidence was reported [2]. A gradient of incidence and mortality between North Western and South Eastern Europe has been observed: new CRC cases increased in historically low-risk areas such as Spain and Eastern Europe [3]. This growing incidence reflects modifications in lifestyle behaviours and their consequences related with ‘westernisation’ such as obesity, physical inactivity, heavy alcohol consumption, high red meat consumption and smoking.
Mortality has declined progressively in many Western countries: this can be attributed to cancer screening programmes, removal of adenomas, early detection of cancerous lesions and availability of more effective therapies, chiefly for early stage disease. Mortality rates for CRC in the European Union (EU) vary between 15 and 20 of 100 000 males and between 9 and 14 of 100 000 females and have decreased in both Western and Northern Countries, particularly in females. In 10 years (1997–2007), EU mortality declined by 6% per quinquennium in men and 8% per quinquennium in women. The analysis updated to 2007 showed a greater reduction of the mortality rate in the young population (aged 30–49 years) with ∼10% per quinquennium [4]. In Europe, the 5-year survival for colon cancer in different geographical settings ranged from 28.5% to 57% in men and from 30.9% to 60% in women: the pooled estimation for 51 registries of 23 countries is 46.8% in men and 48.4% in women [5].
The risk of developing colon cancer depends on factors which can be classified into lifestyle or behavioural factors (such as smoking, high red meat consumption, obesity, physical inactivity) and genetically determinant factors. According to international guidelines [6, 7], screening tests are stratified according to the personal risk of disease. Age is considered the major unchangeable risk factor for sporadic colon cancer: nearly 70% of patients with colon cancer are over 65 years of age, and this disease is rare before 40 years even if data from SEER and Western registries show an increased incidence in the 40–44 years group and a decrease in the oldest groups [8].
Individuals with: are considered at high risk of colon cancer and must be actively screened and, in cases of inherited syndromes, also referred for genetic counselling [7, 9].
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a personal history of adenoma, colon cancer, inflammatory bowel disease (Crohn's disease and ulcerative colitis),
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significant family history of CRC or polyps,
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an inherited syndrome (5–10% of all colon cancers) such as familial adenomatous polyposis coli and its variants (1%), Lynch-associated syndromes [hereditary non-polyposis colon cancer (3–5%)], Turcot-, Peutz-Jeghers- and MUTYH-associated polyposis syndromes,
screening principles
The aim of screening is to detect a pre-cancer condition in a healthy population, as well as very early-stage malignancies which can be treated with a clearly curative intention.
For average-risk populations, the European Guidelines for quality assurance in CRC screening and diagnosis [10] provide ‘guiding principles and evidence-based recommendations on quality assurance which should be followed when implementing CRC screening using the various modalities currently adopted in publically mandated programmes in EU member States’.
The recommendations are:
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Only the faecal occult blood test (FOBT) for men and women aged 50–74 (or 70) years has been recommended to date. In average-risk populations, the guaiac (g) FOBT reduced mortality from CRC by ∼15% [I] in different age groups [I, V]. The benefit from annual screening appears to be greater than for biennial screening and the test interval should not exceed 2 years [II, B].
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Faecal immunochemical testing appears to be superior to gFOBT with respect to the detection rate and positive predictive value for adenomas and cancer [III]; the test interval should not exceed 3 years [V].
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Flexible sigmoidoscopy (FS) reduces CRC incidence and mortality when carried out in an organised screening programme [II]; the optimal interval should not be <10 years and may even be extended to 20 years [IV, C]. The preferred age range is likely to be between 55 and 64 years [III, C]. After age 74, average risk FS screening should be discontinued, given the increasing co-morbidity in this population [V, D].
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Colonoscopy: limited evidence exists on the efficacy in reducing CRC incidence and mortality [III]. A note of caution is the observation that colonoscopy screening may not be as effective in the right colon as in other segments of the large bowel [IV]. The age range is 50–74 years [V, D] with the optimal age for a single colonoscopy being around 55 years [IV, C]. The optimal interval should not be <10 years and may even be extended up to 20 years [III, C].
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Combination of FOBT and sigmoidoscopy: there is no current evidence for extra benefit from adding a once-only sigmoidoscopy to FOBT screening [II].
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New screening technologies are still under evaluation: computed tomography (CT) colonography, stool DNA testing and capsule endoscopy should therefore not be used for screening in the average-risk population [V, D].