Introduction Colorectal cancer (CRC) is the second leading cause of cancer related deaths in the United Kingdom. Colonoscopy is recommended first line investigation for CRC. Most studies recommend counselling patients undergoing colonoscopy about a “miss rate” of up to 6%.¹The aim of this retrospective study was to evaluate the frequency of post colonoscopy colorectal cancer (PCCRC) in a District General Hospital.

Method Data for all patients with a new diagnosis of CRC were obtained from our local colorectal cancer services between Jan 2011 to Sept 2014. We identified all patients who have had colonoscopy within 36 months of a CRC diagnosis. PCCRC was defined as those who had colonoscopy within 6–36 months of diagnosis, whereas the cancers were classified as “detected” if diagnosis was made within 6 month of preceding colonoscopy. Patients with incomplete colonoscopy were excluded.

Results 494 patients were diagnosed with CRC. Of these, 161 patients had a colonoscopy within 36 months preceding diagnosis. 2.5% (4/161) patients were found to have PCCRC. 75% were male and mean age of the patients was 77 years (range 61–86 years). Bowel preparation was reported to be good in all procedures.

The location of the PCCRC was sigmoid (2), descending colon (1) and transverse colon (1). The indication for colonoscopy was anaemia (2), bleeding per rectum (1) and Crohn’s colitis surveillance (1). Only 1 colonoscopy detected colonic polyp, tubulovillous adenoma with high grade dysplasia; however this was not followed up as per guidelines. The mean time between colonoscopy and definitive colon cancer diagnosis was 30 months (range 19–36 months).

All patients with PCCRC died with a mean survival time of 376 days from the time of cancer diagnosis. Two of these four patients had metastatic disease at the time of diagnosis with one of the patient had extensive metastasis and died within 16 days of diagnosis.

Conclusion In our study, rate of PCCRC was 2.5%, although this rate is low compared to most studies²but it has serious implications and may lead to diagnosis at an advanced stage. It is prudent to audit the miss rate of colonoscopy to improve colonoscopy quality and the rate of PCCRC occurrence should be incorporated as a quality indicator of a colonoscopy service

Disclosure of interest None Declared.

References

1. Bressler B, Paszat LF, Chen Z et al. Rates of new or missed colorectal cancers after colonoscopy and their risk factors: a population-based analysis. Gastroenterology 2007;132:96–102

2. Morris EJ, Rutter MD, Finan PJ et al. Post-colonoscopy colorectal cancer (PCCRC) rates vary considerably depending on the method used to calculate them: a retrospective observational population-based study of PCCRC in the English National Health Service. Gut2014. doi: 10.1136/gutjnl-2014-308362