Colonoscopy and tumors

A quantitative assessment of the risks and cost savings of forgoing histologic examination of diminutive polyps (Kessler et al., Endoscopy 2011 [1])

Colonoscopy with polypectomy reduces the lifetime risk of colorectal cancer (CRC) [2]. Accurate histological assessment of excised polyps informs two clinical pathways: surveillance recommendations, which are primarily based on the adenoma vs. hyperplastic polyp differentiation; and, less commonly, invasive disease, which requires further therapy. In routine practice the vast majority of polyps that are removed are ≤ 5 mm (diminutive polyps); only 50 % are adenomas, and advanced histology (villous component or high grade dysplasia, which are currently undetectable endoscopically) or unsuspected invasive disease is rare. Thus, the primary importance of formal histology in patients with diminutive polyps is to determine the surveillance interval, with little if any impact on immediate clinical outcomes. The advent of worldwide CRC screening programs, improved imaging technology, and the increasing focus on quality and adenoma detection will increase the frequency of diminutive polypectomy substantially and consequently the burden and cost of histological assessment for diminutive polyps. Recent data suggests that user-friendly, efficient “push button” technology, such as narrow-band imaging (NBI), can reliably distinguish adenomas from hyperplastic polyps, and consequently real-time endoscopic diagnosis (without formal histological assessment) may be a more efficient and cost-effective means of handling the pathological diagnosis and surveillance recommendations in this diminutive polyp subgroup [3] [4]. However, incorrect surveillance practice carries financial and clinical implications. Surveillance colonoscopy performed too often increases costs and the risk of adverse events, whereas surveillance colonoscopy that is performed less often than required may increase the risk of interval cancer with its associated costs.

Kessler et al. used a comprehensive decision analysis model to examine the effects of two different management strategies for diminutive polyps on surveillance intervals, costs, and clinical outcomes from a database cohort of 10 060 consecutive patients undergoing colonoscopy in routine clinical practice [1]. The management strategies were: submission of all polyps for pathologic evaluation; or endoscopic determination of the histology of all diminutive polyps followed by endoscopic resection of all polyps, discarding the diminutive polyps and submitting only non-diminutive polyps [ ≥ 6 mm] for pathologic evaluation. The adverse clinical effects of incorrect surveillance, which encompasses major colonoscopy complications (bleeding and perforation) and missed cancers, were assessed by using frequencies derived from the literature. These were expressed as the number needed to harm, which is the inverse of the absolute risk.

Analysis of the raw data confirms how much energy is expended on these innocuous lesions. Altogether, 4474 patients with a total of 9042 diminutive polyps were identified for analysis and these were divided into four groups. Group 1, 45 % of patients with at least one diminutive polyp had only a single diminutive polyp; 58 % of the single diminutive polyps were hyperplastic and 42 % were tubular adenomas. Group 2, 24 % of patients had either two diminutive polyps or one diminutive polyp and one additional polyp that was not a large adenoma. Within this group, 59 % of patients had at least one adenoma, and the remaining 41 % had only hyperplastic polyps. Group 3, 26 % of patients had three or more polyps, none of which was a large adenoma (≥ 10 mm). Within this group, 25 % had only hyperplastic polyps, 34 % of patients had one or two non-advanced adenomas, and 41 % had at least one advanced adenoma or three or more adenomas. Group 4, nearly 6 % of patients had one or more large adenoma and possibly other polyps in addition to at least one diminutive polyp. Advanced histology was found in 0.6 %, 2.3 %, 4.5 %, and 47.4 % of patients in groups 1 – 4, respectively, and high-grade dysplasia was found in 0.1 %, 0.5 %, 1.5 %, and 7.2 % of patients in groups 1 – 4, respectively. Fundamentally, only the smallest group of patients (6 % of the total) with at least one large adenoma, were at any significant risk of advanced histology or high grade dysplasia.

When comparing the two management strategies of complete histology against the approach of endoscopic diagnosis and the discarding of diminutive polyps, total incorrect surveillance was 2 % vs. 12 %, the latter comprising approximately equal frequencies of over- and under-surveillance. For the entire group the estimated cost of incorrect surveillance was US$36 per patient, and the estimated saving from forgoing pathology was US$210 so the net cost savings from the “assess and discard” strategy was US$174.01 per patient. Based on the annual volume of colonoscopy in the USA, the annual up-front cost saving of forgoing pathologic assessment of diminutive polyps would exceed a billion dollars. The number needed to harm, because of major post-polypectomy bleeding, perforation, or missed interval cancer, was 7979, equating to an absolute risk of 0.0125 %. The expected life lost per person from using longer than recommended follow-up intervals ranged from 8 to 35 days for different combinations of sex and number of polyps. Clearly the “assess, resect, and discard” strategy for diminutive polyps holds promise for major cost savings with minimal adverse clinical consequences. Further studies are needed to confirm generalizability and, finally, endorsement by major endoscopy societies will be necessary.

• References

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