Protective association of colonoscopy against proximal and distal colon cancer and patterns in interval cancer.
BACKGROUND
The protective effect of colonoscopy against proximal colorectal cancer is variable and depends on the detection and complete removal of precancerous polyps.


OBJECTIVE
To estimate the efficacy of colonoscopy in a medical center with open-access screening colonoscopy since 1998.


METHODS
Nested case-control study with incidence density sampling.


METHODS
University-affiliated Veterans Affairs Medical Center.


METHODS
Colorectal cancer (CRC) cases and control subjects selected from screening age patients matched by age, gender, and date of first primary care visit.


METHODS
Colonoscopy preceding the CRC diagnosis date.


RESULTS
A total of 20.2% of CRC cases had a colonoscopy in the preceding 10 years compared with 49.0% of control subjects (adjusted odds ratio [aOR], 0.20; 95% confidence interval [CI], 0.11-0.34). Colonoscopy was strongly associated with decreased odds of both distal CRC (aOR, 0.16; 95% CI, 0.07-0.34) and proximal CRC (aOR, 0.26; 95% CI, 0.11-0.58). The fraction of cases attributed to interval cancers was 10.5%. Missed lesions predominantly localized to the cecum and rectum, and recurrent lesions clustered in the hepatic flexure. Cecal intubation rate was 93% (98% in adequately prepped patients), and the adenoma detection rate was 45.2% in the control group.


CONCLUSIONS
Single-center, retrospective case-control design.


CONCLUSIONS
In an open access colonoscopy program characterized by a high cecal intubation rate and adenoma detection rate, colonoscopy was strongly associated with reduced odds of both distal and proximal CRC. Among interval cancers, missed lesions clustered in the cecum and rectum and recurrent lesions in the hepatic flexure.
Department of Medicine, Division of Gastroenterology, San Francisco Veterans Affairs Medical Center and University of California San Francisco, San Francisco, California, USA.
Amandeep K
AK
Shergill
Department of Medicine, Division of Gastroenterology, San Francisco Veterans Affairs Medical Center and University of California San Francisco, San Francisco, California, USA; Joint Doctoral Program in Public Health, University of California San Diego and San Diego State University, San Diego, California, USA.
Erin E
EE
Conners
Department of Medicine, Division of Gastroenterology, San Francisco Veterans Affairs Medical Center and University of California San Francisco, San Francisco, California, USA.
Kenneth R
KR
McQuaid
Department of Medicine, University of California San Francisco, San Francisco, California, USA.
Sara
S
Epstein
Department of Medicine, Division of Gastroenterology, San Francisco Veterans Affairs Medical Center and University of California San Francisco, San Francisco, California, USA.
James C
JC
Ryan
Department of Medicine, Division of Gastroenterology, San Francisco Veterans Affairs Medical Center and University of California San Francisco, San Francisco, California, USA.
Janak N
JN
Shah
Department of Medicine, Division of Gastroenterology and Hepatology, Institution: University of Washington, Seattle, Washington, USA.
John
J
Inadomi
Department of Medicine, Division of Gastroenterology, San Francisco General Hospital and University of California San Francisco, San Francisco, California, USA.
Ma
M
Somsouk
D000230:Adenocarcinoma / Q000175:diagnosis / Q000453:epidemiology* / Q000473:pathology; D000236:Adenoma / Q000175:diagnosis / Q000453:epidemiology* / Q000473:pathology; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D015331:Cohort Studies; D003106:Colon / Q000473:pathology; D003113:Colonoscopy / Q000706:statistics & numerical data*; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000453:epidemiology* / Q000473:pathology; D055088:Early Detection of Cancer / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D065840:Protective Factors; D012007:Rectum / Q000473:pathology; D012189:Retrospective Studies; D014481:United States; D014493:United States Department of Veterans Affairs