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We write with concern regarding the recent “Screening guidelines for colorectal cancer and polyps in patients with acromegaly” (
). While there is little doubt that patients with acromegaly have an increased risk of developing colorectal cancer, the exact nature of this risk is far from clear. The endocrine literature has witnessed a significant debate, polarising two separate views. Jenkins and Fairclough advocate screening while Renehan et al suggest that the risk of colorectal cancer formation does not warrant screening or surveillance.1,2 The recommendations by Jenkins and Fairclough for a national screening programme, endorsed by the BSG and ACPBG, are based largely on a series of 222 patients enrolled in a colonoscopy programme in one centre. The principal finding of this study was a 13–14-fold increase in the risk of colorectal cancer in acromegalics relative to the general population. This is at odds with larger studies (n=1362,3 n=1041,4 n=16345) which overall indicate an increased colorectal cancer risk of 2.5–3-fold. Jenkins and Fairclough advocate an intensive screening protocol beginning at 40 years (citing the youngest case in their 222 case series occurring at 39 years although mean age of the 10 patients with cancer was 67 years). They advocate repeat colonoscopy at five years, or three yearly if at increased risk (as determined by adenoma at initial colonoscopy or increased IGF-1 levels). Renehan et al however conclude that there is no increased incidence of colonic adenomas compared with a normal control population (generated from postmortem and colonoscopy data).
These data may differ because of the controls used and this probably also explains their variance with the larger studies.6 Based on the current literature, an independent view is that patients might benefit from a single sigmoidoscopy or colonoscopy at approximately 55 years of age. However, no study suggests a risk of proximal neoplasia that warrants the risks and difficulties of a colonoscopy. Guidelines for familial colorectal cancer screening suggest that colonoscopic surveillance is only warranted for a lifetime risk of 1 in 10 or greater.7
It is therefore both worrying and disappointing that the published guidelines reflect only one point of view of a very polarised debate. This may reflect the process of guideline formation in which experts were requested to submit guidelines.7 At present there is insufficient data to advocate an intensive colorectal cancer screening programme for patients with acromegaly. The increased risk of colorectal cancer is modest and the potential risk of colonoscopy in acromegalic patients is considerable. These guidelines need to be challenged before gastroenterologists are forced into a practice which is not evidence based and may be detrimental to patient well being.
We thank Drs Perry and Kane and Professor Stewart for their contribution to the debate on this topic. The correspondents acknowledge that patients with acromegaly have an increased risk of developing colorectal cancer; the question really concerns the magnitude of the cancer risk and the relative risk of colonoscopy.
As stated in the guidelines, our recommendations were based on aggregated data from a total of 13 prospective colonoscopic studies involving almost 700 patients with acromegaly. The relative risk was derived from the prevalence of colorectal cancer in patients with acromegaly compared with the asymptomatic matched control populations in the same studies. On this basis, there is also a clear increase in the risk of tubular adenomas. We believe this to be the best quality data on which to base recommendations. We have previously given the reasons why we think that control data generated from the postmortem studies referred to by Renehan et al are of poorer quality.
One of the major aims of a screening programme is to prevent the development of colorectal cancer by detection and removal of adenomas. We therefore feel that it is sensible to begin this preventative screening at the age of 40 years in this group of patients who seem to be at relatively high risk. The recommendations will probably change in the light of further information about the pathophysiology and behaviour of colorectal neoplasia in acromegaly, and could prove to have been over cautious. However, until then, a policy of early screening examinations and data collection seems prudent.
In addition to our own observations, several other studies have reported an increased prevalence of right sided colonic neoplasia in acromegaly. We therefore believe it would be unwise to accept the suggestion that a single sigmoidoscopy is a sufficient screening procedure. At this stage, full colonoscopy is warranted, both for the sake of the individual and for the sake of providing a firm basis on which to make recommendations. Furthermore, on the rare occasions on which colonoscopy is not complete, either a barium enema or a virtual colonoscopy should be performed.
The risks of colonoscopy in good hands are minimal. We have not encountered a single complication in over 500 procedures in patients with acromegaly but clearly these are not procedures to be undertaken by the inexperienced. In this same 500 examinations, we have detected 10 asymptomatic cancers, as well as numerous adenomas. Thus based both on the literature and on our own experience, the risk of undetected colonic cancer far outweighs the theoretical risks of colonoscopy.
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