Why screening and who is benefiting?

Colorectal cancer (CRC) is a pandemic disease causing massive global public health problems and economic pressures. It is becoming more common in developing countries and is still increasing in the developed world. The disease is also perceived to be one of the ‘avoidable’ and treatable cancers for which we have clinical, social and economical duties to prevent and furthermore the tools to do so. It is a cancer that that has an identifiable precancerous lesion that is amenable to resection, the adenoma. Since the concept of the adenoma carcinoma sequence publicized by Dr Morson in the 1960s, all attention has been focussed on the adenoma as the ‘sole’ premalignant condition. This concept has, however, been challenged of late by the finding of significant cases of cancers arising de novo or on a background of a flat adenoma, which is more difficult to recognize by the routinely used endoscope. To reduce the risk of CRC, the adenoma needs to be removed and hence the concept of colonoscopic screening. The general principles of screening for any disease include the following requirements: the condition to be screened should be common and can cause significant morbidity and mortality. There should be a screening test available which diagnoses the condition reliably and safely. There should be effective treatment. All of these requirements are fulfilled in the National Bowel Cancer Screening Programme (NBCSP). This screens the population between 60 and 69 years, and from April 2010 the upper age group will be raised to 75 years. The process basically is as follows: all patients of the age group of 60–69 years are invited to submit faeces for faecal occult blood (FOB) testing using the guaiacbased technique. If this is positive, then the patient is counselled and offered colonoscopy. The colonoscopy should be carried out in an accredited colonoscopy centre by an accredited endoscopist. Those diagnosed with cancer should be promptly managed. Although it is expected that this whole process will ensure a significant reduction in cancer mortality, there are still several problems accompanying the programme. For example, there is a group of patients who harbour CRC but are FOB negative. In this case, it is imperative that they should not be given the impression of being cancer free. It also means that it is important to improve the sensitivity of FOB. Hol et al. [1] recently showed in a population-based CRC screening trial using immunochemical FOB (IFOB) randomized against guaiac-based FOB that the detection rate was far superior in the IFOB cohort. The authors strongly suggest using the IFOB in screening programmes. This important study needs to be validated before changing national practice in UK. There are other consequences. The Dukes staging system will invariably differ from the nonscreened cohort so that more patients will present with a Dukes A cancer. This will inevitably create a variance from the literature, which classically reported on symptomatic patients. The epidemiological data will have to be adjusted to take the new emerging statistics into account. There will be more cases of malignant polyps (cancer arising in an adenoma) detected in the screening programme than in symptomatic patients. That may be good news, but it begs the question as to what is the best way of treating these cases [2]. This is an opportunity to undertake a large multicentre study to determine the best way of treating this condition as the literature is still divided. Furthermore, how should patients with positive FOB and negative colonoscopy be managed? One review from Canada, where CRC is very common and screening has been instituted, addresses this question [3]. It shows that when there is positive FOB and the patient undergoes both upper and lower gastrointestinal endoscopy, the yield for upper GI pathology is significant. These authors, however, argue that in those patients with a positive FOB test and negative colonoscopy, it is not cost effective to perform routine upper GI endoscopy unless the patient is anaemic, symptomatic or has risk factors for gastric cancer. What happens to the population outside the screening age group? In an important study, Shellnut et al. [4] looked at the appropriateness of restricting the screened age group and found that not screening individuals under 50 and over 75 years would miss 49% of patients treated in their institute. The current issue of colorectal disease carries two important articles by Harmston and colleagues and Ellul and colleagues addressing two different aspects of screening. The former looked at 200 patients with CRC from the much larger cohort of a screened population included in the NBCSP and analysed their symptoms. They found that 70% had significant symptoms such as rectal bleeding, tenesmus, change in bowel habit, abdominal pain and perianal discomfort. They argued that with proper public awareness, these symptoms would have triggered referral to an appropriate practitioner through the routine channel(s) acknowledging, however, that these patients