Risk of colorectal cancer in general practice patients presenting with rectal bleeding, change in bowel habit or anaemia


Professor Ross Lawrenson, Peter Rothwell Academic Centre, Waikato Clinical School, Waikato Hospital, Private Bag 3200, Hamilton, New Zealand (e-mail: lawrensr@waikatodhb.govt.nz).


The aim was to use data routinely collected in general practice to assess the absolute risk of colorectal cancer in patients newly presenting to their general practitioner (GP) with relevant symptoms. Three cohorts were identified from patients attending a sample of UK general practices. Patients with new symptoms of rectal bleeding, changes in bowel habit or anaemia were identified, and their incident rate for colorectal cancer and the positive predictive value (PPV) of each symptom in the following 12 months were calculated by age and gender. The total population over the age of 40 years was 2.8 million, and 9143 incident cases of colorectal cancer were identified. A total of 67 164 patients (28% men) were identified with anaemia, 27 524 (40% men) with changes in bowel habit and 44 741 (48% men) with rectal bleeding. For each cohort, the absolute risk rose with increasing age, and men were twice as likely to develop colorectal cancer. The PPV for developing colorectal cancer in the subsequent 12 months in those aged 60–69 years with anaemia was 3.02% for men, 1.38% for women; with changes in bowel habit 6.89% for men, 2.42% for women; and with rectal bleeding was 5.99% for men, 3.50% for women. A combination of any two signs and symptoms doubled the risk of an underlying cancer. In UK general practice, men are less likely to present with symptoms and signs of colorectal cancer compared with women, but after investigation are much more likely to have a colorectal cancer diagnosed. This should be taken into account in guidelines for referral.