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Canadian Journal of Gastroenterology and Hepatology
Volume 2016 (2016), Article ID 4768728, 6 pages
Research Article

Interval Colorectal Cancers following Guaiac Fecal Occult Blood Testing in the Ontario ColonCancerCheck Program

1Institute for Clinical Evaluative Sciences and the University of Toronto, 2075 Bayview Avenue, Toronto, ON, Canada M4N 3M5
2Division of Gastroenterology, Sunnybrook Health Sciences Centre and the University of Toronto, 2075 Bayview Avenue, Toronto, ON, Canada M4N 3M5
3Department of Surgery, St. Michael’s Hospital and the University of Toronto, 30 Bond Street, Toronto, ON, Canada M5B 1W8
4Cancer Care Ontario and the University of Toronto, 620 University Avenue, Toronto, ON, Canada M5G 2L7

Received 18 February 2016; Accepted 26 April 2016

Academic Editor: Brian Bressler

Copyright © 2016 Lawrence Paszat et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Background. This work examines the occurrence of interval colorectal cancers (CRCs) in the Ontario ColonCancerCheck (CCC) program. We define interval CRC as CRC diagnosed within 2 years following normal guaiac fecal occult blood testing (gFOBT). Methods. Persons aged 50–74 who completed a baseline CCC gFOBT kit in 2008 and 2009, without a prior history of CRC, or recent colonoscopy, flexible sigmoidoscopy, or gFOBT, were identified. Rates of CRC following positive and normal results at baseline and subsequent gFOBT screens were computed and overall survival was compared between those following positive and normal results. Results. Interval CRC was diagnosed within 24 months following the baseline screen among 0.16% of normals and following the subsequent screen among 0.18% of normals. Interval cancers comprised 38.70% of CRC following the baseline screen and 50.86% following the subsequent screen. Adjusting for age and sex, the hazard ratio (HR) for death following interval cancer compared to CRC following positive result was 1.65 (1.32, 2.05) following the first screen and 1.71 (1.00, 2.91) following the second screen. Conclusion. Interval CRCs following gFOBT screening comprise a significant proportion of CRC diagnosed within 2 years after gFOBT testing and are associated with a higher risk of death.