Screening Colonoscopy Should Be Available to All.
James W. Fleshman M.D.
Wells, K. and J. Fleshman (2019). “Screening Colonoscopy Should Be Available to All.” JAMA Surg Apr 17. [Epub ahead of print].
In a retrospective review of 16,000 patients in a systemwide experience of screening colonoscopy, Sarvepalli et al determined that the association of endoscopist specialty (surgeon or gastroenterologist) with adenoma detection rate was insignificant. This counters previously reported lower quality for colonoscopies and increased risk of missed adenomas and interval cancers by surgeons and confirms that colonoscopic quality indicators are adequately met by both gastroenterologists and nongastroenterologists. Sarvepalli et al do report differences between specialties not owing to random features of the endoscopists and other confounders, specifically, a decrement in the proximal sessile serrated adenoma (SSA) detection rate of 2.3% by surgeons vs 5.6% by gastroenterologists. The clinical significance of a 3.3% difference in the proximal SSA detection rate is questionable. Proximal SSAs arise via CpG island methylator phenotype pathway, with higher rates of methylation and carcinogenesis occurring in an age-dependent pattern. In a pathology series of 2416 SSAs, SSA-associated carcinoma was diagnosed at a mean age of 76 years vs 67 years among those with carcinoma arising in conventional adenomas. The SSAs do not progress as often or as quickly as conventional adenomas, accounting for their presence in the elderly cohort. In longitudinal computed tomographic colonographic assessment, 22% of SSAs progress vs 41% of conventional adenomas at an annual volumetric growth rate of 12.7% vs 36.4% in conventional adenomas (P = .03). The difference in median age between patients with SSA and SSA-associated carcinoma is 15 years vs a 5-year difference from tubular adenoma to conventional carcinoma, suggesting a 3-fold longer rate of progression to malignancy in SSA. Therefore, a second screening colonoscopy in 10 years would likely detect an early cancer or larger SSA. An SSA-harboring carcinoma represented only 1% of all specimens, which, if applied to the Sarvepalli et al study’s difference of 3.3%, translates into a miss rate of 3 SSA-associated carcinomas per 10 000 colonoscopies. In view of a slower progression of SSA to cancer in most cases, allowing a slightly higher miss rate in surveillance colonoscopy performed by nongastroenterologists might be acceptable. Eventual polypectomy, as less aggressive SSA lesions become larger, would be akin to the management of anal intraepithelial neoplasia III, where frequent observation of an affected mucosal field to remove visible lesions preserves the organ and effectively prevents progression to cancer. This study validates the surgeon in providing a high-quality screening and, more importantly, broadens the limited pool of clinicians to address low national screening rates. The question becomes whether well-trained nonspecialty clinicians with an acceptable adenoma detection rate could also provide screening. (Excerpt from text, p. e1; no abstract available.)