Surveillance after colonic neoplasia: to die of success

The main aims of surveillance colonoscopy are to reduce the incidence and mortality of colorectal cancer (CRC), removing adenomas, and detecting early-stage CRC. However, colonoscopy is an expensive and invasive procedure, and therefore surveillance colonoscopy should be targeted toward the patients who are most likely to benefit, and at the minimum frequency required to provide adequate protection against the development of cancer [1]. No studies about postpolypectomy surveillance have directly demonstrated the benefit of a reduction in CRC incidence or mortality; however, some studies have suggested that follow-up colonoscopy appears to be effective in reducing the risk of CRC among patients with previous adenoma [2] [3], and this is the rationale for surveillance colonoscopy. Moreover, surveillance intervals are arbitrary and not based on clinical trials, and available evidence is scarce and of low quality. Although the main outcome indicator used in postpolypectomy surveillance is advanced adenoma, this is only a surrogate marker of the main end point, which is CRC. The rate of progression from advanced adenoma to CRC is also unknown, but is probably low [4].

In this issue of Endoscopy, two articles address the question of how we are using surveillance colonoscopy. In the first article, Sint Nicolaas et al. from The Netherlands investigated indications for 4800 consecutive colonoscopies, focusing on repeated procedures in order to determine the number, reasons, and yield of these additional explorations [5]. It is quite significant that in this study almost one-third of the procedures were repeat colonoscopies, revealing the importance of repeated testing in daily clinical practice. The authors divided their sample into early (< 1 year) and late (> 1 year) follow-up colonoscopies. Surveillance after adenoma removal was the main indication for these repeat colonoscopies in both cohorts. However, a high number of early follow-up colonoscopies were preceded by a low-quality index procedure, which indicates the absolute importance of quality assurance in order to avoid unnecessarily repeat colonoscopies. Also, almost a quarter of late follow-up studies were repeated because of low-quality baseline colonoscopy, and approximately a half were repeated as surveillance after neoplasia removal in asymptomatic people, which indicates the high importance of both aspects. Based on the recommendations of the American Gastroenterological Association [6], utilization of these surveillance colonoscopies was considered optimal in only 27 % of patients, with clearly higher rates of overuse than underuse.

In the second study, Stock et al. [7], from the German Cancer Research Center, retrospectively explored the utilization and yield of repeat colonoscopies performed within 3 years of baseline by the same physician in order to investigate the main predictors of utilization of additional colonoscopies. The study included 5873 colonoscopies, and also clearly demonstrated a rate of overuse. Moreover, although the authors concluded that there was substantial detection of adenomas during the first 3 years after baseline explorations, the yield of these follow-up colonoscopies was relatively low (especially in procedures performed more than 6 months after baseline), with almost negligible rates of CRC and low rates of advanced adenomas, even when high-risk adenoma was the finding at baseline colonoscopy. This study does not provide information about the quality of the baseline colonoscopies and has the limitation of only considering additional colonoscopies performed by the same physician, therefore underestimating the true rate of repeat procedures. The independent predictors of repeated colonoscopies were younger age, male sex, screen-detected adenomas, inflammatory bowel disease, and early repeat colonoscopy.

Both studies illustrate three important facts: 1) surveillance is one of the main indications for colonoscopy; 2) there is a high rate of overuse of postpolypectomy surveillance colonoscopy; and 3) the yield of these colonoscopies is low, especially when indications do not conform to guidelines. Taken together, these facts suggest that a high number of inappropriate procedures are filling our endoscopy lists and hampering our ability to retain enough capacity in our endoscopy services to perform colonoscopies that are necessary. This situation is particularly relevant now, as endoscopy demand is increasing due to the implementation of CRC screening programs. Inadequate use of surveillance can be detrimental to the effectiveness and cost-effectiveness of CRC screening programs, a point that is accurately discussed in the Stock study [7]. If we are not careful with postpolypectomy surveillance indications and intervals, CRC screening programs could “die of success,” given that a high number of otherwise asymptomatic adenomas are diagnosed in these screening programs, causing an avalanche of new follow-up colonoscopies. It is the duty of the gastroenterological scientific community to generate new and robust evidence regarding the utility of surveillance after neoplasia resection, and especially regarding appropriate surveillance intervals.

There are several reasons for the inappropriate overuse of surveillance colonoscopy. Foremost could be a lack of knowledge about the natural history of colonic adenomas. It is well established that CRC takes a long time to develop after the colon has been cleared of polyps, and even the common assumption of a 10-year period between colonoscopies might be too conservative [8]. Because advanced adenomas need to be removed once they are detected, any direct observation of their natural history would be unethical. Thus, most available estimates for the progression of adenomas stem from radiological surveillance data or from autopsy series collected prior to the colonoscopy era [4] [9]. Doubts about the quality of the baseline colonoscopy are another reason for the lack of adherence to guidelines and for surveillance colonoscopy overuse. High-quality colonoscopy is required for appropriate surveillance recommendations. In a recent study, factors directly related to quality, such as insufficient bowel preparation or incomplete colonoscopies, were risk factors for the finding of advanced adenomas at follow-up and were as important as adenoma size or number [10]. For this reason, measures that aim to achieve appropriate cecal intubation rates and good bowel cleansing should be guaranteed. To achieve appropriate surveillance indications, quality indicators must be reflected in the endoscopy report in order to provide physicians with the most complete information about the characteristics of endoscopies. The quality of bowel preparation must be clearly reported using validated scales [11]. Moreover, primary quality indicators, such as adenoma detection rate, must be monitored for every endoscopist and endoscopy unit participating in CRC screening programs, and these units should be involved in continuous quality improvement programs.

Finally, a third factor that might influence this high rate of inappropriate surveillance colonoscopy is the lack of evidence regarding surveillance intervals. With some minor differences, the most frequently used guidelines recommend no specific surveillance or routine screening for low-risk adenomas and surveillance colonoscopy in 3 years for advanced adenomas [1] [5]. However, this 3-year surveillance interval is somehow arbitrary because it is not based on results from clinical trials, and it is possible that longer intervals might have the same utility in the prevention of CRC in this population, and better cost-effectiveness. Only one high-quality randomized clinical trial has compared different intervals in surveillance colonoscopy [12], and the results of this study are the only basis for recommending a 3-year surveillance interval after the excision of high-risk adenomas. There is some evidence indicating that the risk of advanced neoplasia could be the same at 5 years after the excision of high-risk adenomas [2], and therefore more research is needed to determine appropriate surveillance intervals. Until now, the majority of research in this field has come from observational studies. We have a problem with surveillance colonoscopy, and we must solve it (as always in medicine) using a scientific approach. Experimental research is needed to appropriately adjust follow-up surveillance strategies and intervals.

• References

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