Comparing adenoma detection rate and type under a state-of-art colonoscopy protocol vs. typical community-based center protocols in community-based practice settings - Implications for cancer protection

Wide variations in adenoma detection and missed adenoma rates are documented. South Carolina's SCOPE-SC program that funded colonoscopy screening for the indigent, presented a unique natural experiment. We compare polyp and adenoma rates at one center implementing a state-of-art colonoscopy protocol, with the remaining centers that lacked three features, two-person technique in colonoscope insertion and manipulation, 3 persons viewing the video screen, and deep sedation with propofol. In addition the center requires gradual colonoscope insertion and withdrawal, emphasizing polyp search and removal throughout the procedure to minimize missed polyps. Objective: a) Compare adenoma rates/characteristics between Site-3 (high case yield-optimized protocol) with comparison sites (typical community-based endoscopy centers), b) Assess cancer protection implications. Results: Of total 665 Year-I clients, Site-3 and comparison sites served 325 and 340 clients respectively, both groups similar on race and gender. Percentages of patients with polyp(s) were 78.4% and 35.3% respectively, and with adenoma(s) 37.5% and 18.2% (both p<0.001). A total of 252 adenomas were removed at Site 3 vs. 86 at comparison sites (Mean Number of Adenomas per patient screened (MNA) 0.78 vs. 0.26, p<0.001). Proportions of adenomas among polyps (PAP) were similar, 35.3% and 42.1%. Excess adenomas found by Site 3 were ≤5 mm (MNA 0.59 Site 3 vs. 0.16; p<0.001)), or 6-9mm (MNA 0.11 vs. 0.05; p<0.01), with no difference for large adenomas. Comparing adenoma histology, advanced histology percentages (high grade neoplasia, villous, tubulovillous, serrated,or carcinoma) were similar, 9.9% vs. 12.8%. Percentages of small, medium and large adenomas showing advanced histology were similar. One 2mm adenoma was an invasive carcinoma. Conclusions: Comparison sites detected fewer adenomas, "missing" adenomas being <9mm. Site-3 "excess" adenoma categories were histologically as advanced as corresponding comparison sites' adenomas. The similarity of Site-3's polyp detection rate to the documented autopsy study rates suggests it is the true population polyp rate in this population. SCOPE-SC patients were uniformly low SES, and teh 2 site groups were similar on race/gender composition. Therefore Site-3 "excess" adenomas may reflect missed adenomas at comparison sites, The disproportionately higher frequency of small adenomas at Site-3, coupled with histologically similar profiles at the two site groups, and the finding of invasive malignancy in one 2mm adenoma lead us to conclude that the magnitude of "missed" small adenomas by comparison sites may have reduced the cancer protection conferred. High rates by Site 3 may validate the utility of its state-of-art protocol to enhance lesion detection and removal.