Colorectal cancer (CRC) can be diagnosed after the onset of symptoms or through screening. Symptoms from the local tumour may be rectal bleeding, abdominal pain and a change in bowel habits. Abdominal distension, nausea and vomiting may also be symptoms resulting from obstruction. An iron deficiency anaemia can be an indicator of colorectal cancer.
A screening programme for colorectal cancer in the Netherlands started in 2014, inviting all persons aged between 55 and 75 for an immunohistochemic fecal occult blood test (iFOBT) every two years.
After a positive iFOBT, participants receive the advice to undergo a colonoscopy. Patients with an increased risk of CRC have an indication for surveillance colonoscopy and do not participate in the screening programme. This includes patients with familiar CRC, a history of adenomas or CRC, or inflammatory bowel disease (IBD).
The diagnosis is based on the histologic confirmation of a biopsy that is obtained via a colonoscopy. The vast majority of colorectal cancer concerns carcinomas, originating from adenomas or from ‘flat / invisible’ dysplasia occurring in IBD. Other histologic types, such as neuroendocrine tumours or lymphomas, are rare. The Tumour, Node and Metastasis (TNM) staging system is the preferred staging system for colorectal cancer. For localised colon cancer, surgery is the only curative treatment. Treatment and prognosis depend on the local and distant extent of the disease. Other treatment options for colorectal cancer may include chemotherapy and radiotherapy.
A malignancy of the colon is coded with ICPC code D75 and a malignancy of the rectum also has code D75. The distinction between colon cancer and rectal cancer cannot be made based on the ICPC-2 code. Other digestive system tumours are coded separately. A benign or unspecified tumour of the digestive system is coded D78. Other malignancies are coded D74 (stomach cancer), D76 (pancreatic cancer) or D77 (oesophageal, gallbladder and liver cancer).
The incidence of colorectal cancer is 0.4 episodes per 1000 patient years, meaning one new diagnosis of CRC in a practice with 1000 patients every two and a half years. A diagnosis before the age of 45 is rare. New diagnoses are sometimes made between 45 and 64 years of age. Incidence is highest in patients older than 65. Link/Figure 1
The FaMe-Net database does not show an increase in the incidence of CRC after the introduction of the screening programme in 2014. It should be noted that the absolute numbers are small.
The prevalence of CRC is 2.9 per 1000 patient years, meaning that among 1000 patients in a year, three seek help from their GP for CRC. Prevalence is somewhat higher among men than women (3.2 compared to 2.7 per 1000 patient years) and increases with age, especially over 65 years. Link/Figure 2
The higher prevalence number compared to incidence reflects that CRC requires ongoing attention from the GP in the years after the initial diagnosis.
The most common initial reason for encounter (RFE) for colorectal cancer is rectal bleeding (D16, in 14% of new diagnoses), followed by an ‘administrative procedure’ (*62, in 11%). This means that the GP receives a letter from the specialist or from the screening programme reporting this new diagnosis or the first abnormal finding that later leads to this diagnosis. Other important initial RFEs are abdominal pain (D01 and D06, which make up 12% of the total). Link/Table 3
After the introduction of the CRC screening programme in 2014, the proportion of new diagnoses of CRC starting with the RFE ‘administrative procedure’ increased. Link/ Table 4 Note once again that the absolute numbers are small.
GPs prescribe medication (*50) in 43% of all episodes of colorectal cancer. Blood tests (*34) are performed by the GP in 15% and diagnostic imaging (*41) in 4%. Referral to a specialist (*67) occurs in 16% of the episodes (Link/Table 5), mostly to gastroenterology but also to internal medicine and surgery. Link/Table 6 These interventions take place partly before and partly after the final diagnosis. All percentages are calculated per episode of CRC per year and not per complete episode. The medication prescribed by the GP in episodes of CRC is most often osmotically acting laxatives. Link/Table 7
Macrae FA, Parikh AR. Clinical presentation, diagnosis, and staging of colorectal cancer. In: UpToDate, Tanabe KK, Shah SM, Grover S (Eds), UpToDate, Waltham, MA, 2023
Choi. Non-conventional dysplastic subtypes in inflammatory bowel disease: a review of their diagnostic characteristics and potential clinical implications. J Pathol Transl Med. 2021 Mar;55(2):83-93.
Dutch multidisciplinary guideline: https://richtlijnen.nhg.org/multidisciplinairerichtlijnen/colorectaal-carcinoom (2014)
