Analysis of colorectal cancer occurrence during surveillance colonoscopy in the dietary Polyp Prevention Trial.
BACKGROUND
Interval colorectal cancer (CRC) occasionally is detected in patients who have recently undergone colonoscopy. Systematic evaluation of CRC detected after colonoscopy could identify ways to improve the quality and the outcome of colonoscopy.


METHODS
This study examined cancer diagnoses in the course of the dietary Polyp Prevention Trial, a randomized study of a dietary intervention on recurrence of adenomatous polyps. An algorithm was developed to classify each cancer into one of 4 etiologies: (1) incomplete removal (cancer at the site of previous adenoma), (2) failed biopsy detection (cancer in an area of suspected neoplasia with negative biopsy specimens), (3) missed cancer (large, advanced stage cancer found at a short interval after colonoscopy), or (4) new cancer (small, early stage cancer after a longer time interval).


RESULTS
Of 2079 patients, 13 had cancer detected over 5810 person years of observation (PYO) (2.2 cases/1000 PYO); 7/13 or 53.8% of patients had either a potentially "avoidable" cancer or one detectable at an earlier time interval because of incomplete removal (4/13) or missed cancer (3/13).


CONCLUSIONS
Interval cancer occurs despite colonoscopy. Improved quality of colonoscopy may have reduced cancer prevalence or resulted in earlier cancer detection in over 50% of prevalent cancers in the dietary Polyp Prevention Trial.
Pabby
Ajay
A
Division of Gastroenterology, Hepatology, and Nutrition, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213, USA.
Schoen
Robert E
RE
Weissfeld
Joel L
JL
Burt
Randall
R
Kikendall
James W
JW
Lance
Peter
P
Shike
Moshe
M
Lanza
Elaine
E
Schatzkin
Arthur
A
D000368:Aged; D000465:Algorithms; D003111:Colonic Polyps / Q000150:complications / Q000175:diagnosis* / Q000517:prevention & control; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology*; D004032:Diet; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance