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 change in bowel habits. Abdominal distension, nausea and vomiting may be symptoms resulting from obstruction. An iron deficiency anaemia can be an indicator for colorectal cancer. Symptoms are often nonspecific.

 

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 for CRC have an indication for surveillance colonoscopy which falls outside the Dutch screening programme. This includes patients with familiar CRC, a history of adenomas or CRC, or inflammatory bowel disease. 

The diagnosis is made by histologic confirmation of a biopsy that is obtained by colonoscopy. The vast majority of colorectal cancer concerns carcinomas, originating from adenomas or flat dysplasia. Histologic types such as neuroendocrine tumours or lymphomas are rare. The Tumor, Node, 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.

In ICPC-2, a malignancy of the colon is coded as D75. A malignancy of the rectum is also coded D75. A 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 as D78. Other malignancies are coded D74 (stomach cancer), D76 (pancreas cancer) or D77 (including oesophageal, gallbladder and liver cancer).

The incidence of colorectal cancer is 0.4 episodes per 1000 patient years, meaning 0.4 new diagnoses of CRC among 1000 patients in a year. 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 3 seek help from their GP for CRC. Prevalence is somewhat higher among men than women (3.2 vs. 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 may behave as a chronic disease, requiring 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 (in 14% of new diagnoses), followed by an ‘administrative procedure’ (in 11%). This means that the GP receives a letter from the specialist or from the screening programme in which (a sign of) this new diagnosis is reported. Other important initial RFEs are abdominal pain (D01 and D06, together 12%). Link/Table 3 

After the introduction of the CRC screening programme, 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.

During episodes of colorectal cancer, GPs prescribe medication in 43% of the episodes. Blood tests are performed by the GP in 15% and diagnostic imaging in 4%. Referral to a specialist occurs in 16% (Link/Table 5), mostly to gastroenterology and also including internal medicine and surgery (Link/Table 6). These interventions occur in part before and in part after the final diagnosis has been made. These percentages are calculated in all episodes of CRC per year and not per complete episode. Medication prescribed by the GP in episodes of CRC is most commonly osmotically acting laxatives. Link/Table 7