In the management of colorectal cancer a crucial role of primary care is to recognise the patient who is likely to have the disease, and to refer them promptly for investigation. Whether the investigations are organised by the general practitioner prior to hospital referral or by the hospital doctor will depend on local circumstances. This section is subdivided into sections on the significant symptoms, the importance of delay in diagnosis, and strategies to reduce delay.

5.1 Important symptoms of colorectal cancer.

1.5% of all patients with colorectal cancer are under 45 years of age, and 85% are over 60.⁸⁰ Rectal bleeding is commonly experienced in the general population and, although it is an important symptom of colorectal cancer,^{81, 82} over half of those experiencing it do not seek consultation.⁸³

The most important symptoms of colorectal cancer appear to be change of bowel habit, rectal bleeding of short duration and blood mixed in the stool.^{81, 84} Iron deficiency anaemia, although not strictly a symptom, is also an important presenting feature, and should always be thoroughly investigated with colorectal cancer in mind.⁸⁵ Although faecal occult blood testing is an effective means of population screening it is too insensitive to be used in guiding investigation of symptomatic patients (see section 2.7.1).²⁹ Evidence level 2+,4

Colorectal cancer risk assessment can be made using the patient’s age and the presence or absence of presenting symptoms and physical signs, shown in Table 2.^{81, 86}

Table 2: Colorectal cancer risk assessment

Patients over the age of 50 years with any of the following symptoms over a period of six weeks should be urgently and appropriately investigated: rectal bleeding with a change in bowel habit to looseness or increased frequency rectal bleeding without anal symptoms palpable abdominal or rectal mass intestinal obstruction.

All patients with iron-deficiency anaemia (Hb<11g/dl in men or<10g/dl in postmenopausal women) without overt cause should be thoroughly investigated for colorectal cancer.

5.2 Effect of delay in diagnosis

Two retrospective cohort studies have been unable to demonstrate any adverse effect of delay in diagnosis.^{87, 88} For example, patients with anaemia and no symptoms have a better survival rate than those with symptoms despite significant delays in diagnosis in the former. Aggressive disease is more likely to cause severe symptoms prompting rapid diagnosis, so that disease which takes a long time to diagnose appears to be associated with similar or even better survival. Evidence level 2+

Reduction in referral delay has not been shown to confer any survival benefit in colorectal cancer, but this should not deter the general practitioner from striving to identify those patients who warrant urgent investigation.

5.3 Strategies to reduce delay in diagnosis of colorectal cancer

Delay in diagnosis occurs at three levels: patient-related, primary care and secondary care. At patient level, delays appear to be due to ignorance of the significance of symptoms and fear of cancer.^{83, 89, 90} Younger patients are more likely to notice symptoms than older patients, but older patients are less likely to delay in presenting to their GP.⁸⁹ Evidence level 3,4

In general practice, incomplete examination, particularly lack of a rectal examination is an important factor ^{87, 91} and referral to a non-surgical specialty is associated with significant delay.⁸⁸ When the patient reaches hospital, delay is caused by failure to initiate appropriate investigations, and failure to complete investigation, especially in iron deficiency anaemia. Both barium enema and colonoscopy have a false negative rate, and, especially in iron deficiency anaemia, and also in patients with with persistent significant symptoms, a single negative result should not be accepted. Evidence level 2+,4

Patient groups at risk of colorectal cancer, especially those over 50 years of age, should be informed about significant symptoms and encouraged to seek medical attention early should they develop such symptoms.

General practitioners should perform a thorough abdominal and rectal examination on all patients with symptoms suspicious of colorectal cancer.

When a patient presents with suspicious symptoms or signs, they should be urgently investigated and referred to a surgical unit with a declared interest in colorectal cancer.