Colorectal cancer and rectal bleeding in primary care

Editor—Du Toit et al's finding of a one in 10 chance of patients over age 45 presenting with rectal bleeding and subsequently being diagnosed with colorectal cancer is comparable to other recent studies,¹,² but their data were collected from a single rural practice in the United Kingdom, including less than 300 patients. A recent population based, case-control study consisting of over 1500 patients has shown that residence in a rural area was associated with an increased risk of colon cancer (odds ratio 1.4, 95% confidence interval 1.1 to 1.8).³ However, a large epidemiological study of around 500 000 patients shows that black men who reside in metropolitan areas have a higher risk of colorectal cancer than black men who reside in rural areas.⁴ Both these studies have evaluated populations in the United States, but UK populations are similar. It is therefore important to consider both urban and rural cohorts for such studies for precise positive predictive values that may be useful for the population in general.

The findings of du Toit et al also bring into question which referral pattern to use for these young patients with rectal bleeding alone. Referral under the two week wait rule would increase the numbers of patients referred as urgent cases to gastroenterologists and colorectal specialists but may also increase the yield of cancers diagnosed. Time to treatment may fall, as referral lag time may need to be reduced for quicker treatment for colorectal cancers in the UK.⁵ With targets such as 18 weeks and the 62 day rule for treatment and with screening for colorectal cancer starting this year, the burden on the endoscopy services is potentially huge. Lower gastrointestinal endoscopy should be further organised, along with collaboration with radiological diagnostics such as computed tomographic colonography, to ensure that efficient diagnosis of colorectal cancer continues in the UK as referrals increase.