Patients whose colonoscopies were performed by endoscopists with high completion rates were less likely to receive a diagnosis of colorectal cancer 6-36 months later, compared with patients whose colonoscopies were done by endoscopists with lower completion rates, reported Dr. Nancy N. Baxter and colleagues in the January issue of Gastroenterology.
The study drew on five databases comprising virtually all residents of Ontario, wrote Dr. Baxter of the department of surgery at the University of Toronto. Patients were included in the analysis if they had colorectal cancer (CRC) diagnosed in 2000-2005 and had had a colonoscopy 6-36 months prior to diagnosis (Gastroenterology 2011; 140:65-72).
[Bowel Prep Affects Interval To Next Colonoscopy]
Cancers for which a primary site could not be determined were excluded. Additionally, all patients had to be older than 20 years, have no previous CRC history, and have no history of Crohn’s disease or ulcerative colitis.
Endoscopist specialty was ascertained through the Ontario Physicians Human Resources Data Centre, and endoscopist volume was determined by taking the yearly average of all coded colonoscopies performed in the 2 years prior to the date of the colonoscopy in question.
Polypectomy rate was the proportion of colonoscopies associated with a code indicating removal of a polyp larger than 3 mm over the same 2-year period, and completion rate was the proportion of colonoscopies performed by the relevant endoscopist that were complete to the cecum.
Overall, more than 34,000 patients were diagnosed with CRC during the study period, and 14,064 met the study criteria.
Of these, 1,260 (9.0%) were considered to have a postcolonoscopy colorectal cancer (PCCRC), defined as a "CRC within 3 years following a colonoscopy in which the cancer was not detected," wrote the authors.
"After controlling for patient and endoscopy factors, patients undergoing colonoscopy performed by an endoscopist with a completion rate of 95% or greater were less likely to have a PCCRC than if performed by an endoscopist with a less than 80% completion rate for proximal [odds ratio, 0.72; 95% confidence interval, 0.53-0.97] and distal [OR, 0.73; 95% CI, 0.54-0.97] cancers," wrote Dr. Baxter.
Polypectomy rate was also associated with PCCRCs, at least in the proximal colon. Endoscopists with polypectomy rates greater than 30% had an OR of 0.61 for proximal PCCRC, compared with endoscopists whose polypectomy rates were less than 10% (95% CI, 0.42-0.89), they wrote.
Endoscopist specialty played a role as well. Compared with gastroenterologists, endoscopists who were identified as "other" specialties (excluding surgeons) had an OR of 1.87 for proximal PCCRCs (95% CI, 1.34-2.60), and 1.67 for distal cancers (95% CI, 1.13-2.46).
Setting was important too: Colonoscopies performed in a nonhospital setting had an OR of 1.88 for proximal PCCRCs (95% CI, 1.2-2.92), and an OR of 1.67 for distal PCCRCs (95% CI, 1.13-2.46).
The authors did not find any significant relationship between polypectomy rate and the diagnosis of distal PCCRCs, or between procedure volume and any PCCRCs.
The authors conceded several limitations to their study, including the possibility of errors in coding (from which their data were derived).
"Additionally, we could not assess a number of other aspects of care that are likely to have an impact on colonoscopy performance and effectiveness, including factors such as quality of preparation and sedation," they wrote.
Moreover, although the study does show that endoscopist completion rates, polypectomy rates, and specialty are "meaningful quality indicators," the authors wrote, "it is less clear ... [that] use of these indicators in performance management would lead to an improvement in the quality of colonoscopy or a reduction in the number of PCCRC."
The authors stated that they have no conflicts of interest relative to this study, which was funded by an American College of Gastroenterology Cancer Prevention Action Plan Grant, as well as the Ontario Institute for Cancer Research, and Cancer Care Ontario.