Introduction
Colonoscopy is the gold standard for diagnosing colorectal cancer (CRC)1, with post-colonoscopy colorectal cancer (PCCRC) defined by the World Endoscopy Organization (WEO) as CRC diagnosed between 6 and 48 months after a negative colonoscopy2. PCCRC rates vary from 2.5% to 7%2, and the prognosis of PCCRC is generally poorer than that for CRC detected during colonoscopy3.
Aims & Methods
To evaluate the risk factors associated with PCCRC in a major tertiary medical center.
We analyzed all consecutive colonoscopic procedures conducted between 2001 and 2019. Data was retrieved from electronic medical records (EMR) and cross-referenced with the Israeli Cancer Registry. We defined PCCRC based on the WEO criteria, and two physicians independently confirmed potential PCCRC cases to ensure data accuracy. Root-cause analysis of PCCRC was performed according to the WEO algorithm as follows:
A) possible missed lesion, index examination adequate;
B) possible missed lesion, index examination inadequate;
C) detected lesion, not resected; or
D) likely incomplete resection of previously identified lesion.
We then identified colonoscopy-detected CRCs (CDCRC, controls) and compared them to the PCCRC cases at a ratio of 1:3. We assessed patient median age at the procedure, gender, religion, family history of CRC, diabetes, smoking status, body mass index (BMI), obesity (defined in the EMR or BMI > 30) and endoscopic parameters: colonoscopy indication [surveillance (follow-up colonoscopy according to recommendations), abnormal imaging, patient symptoms], adequate Boston Bowel Preparation Scale (BBPS>6 and >2 in all segments), cecal intubation rate, diverticulosis, rectal retroflection, and tumor location.
Multivariable logistic regression assessed the association of multiple factors (endoscopy indications and obesity) with PCCRC, maintaining a 95% confidence interval (CI).
Results
Out of 54,154 colonoscopies, 2,339 patients were diagnosed with CRC, of which 49 (2.1%) were confirmed PCCRCs, while 2,157 (92.2%) were detected during colonoscopy. Of patients with PCCRC, 65.4% (n=32) had adequate BBPS, and 91.8% (n=45) cecal intubation was documented. The two most common reasons for PCCRC were category A (n=29, 59.1%), and category B (n=17, 34.6%), although in a lesser extent. We then compared PCCRC cases to 150 randomly selected CDCRC cases. Significant differences in patient characteristics included BMI>30 (p = 0.041) and obesity (p=0.015). Statistically significant endoscopic factors included colonoscopy indication (p < 0.001), cecal intubation rate (p < 0.001), and tumor location (p < 0.001). As expected, PCCRC was more commonly detected in the right colon (n=24, 55.8%) or rectum (n=12, 27.9%). Multivariable logistic regression revealed that patients with abnormal imaging as a colonoscopy indication had a lower risk for PCCRC (adjusted odds ratio (aOR) = 0.148, 95% CI: 0.033-0.455), while patients that performed colonoscopy for surveillance had a higher risk (aOR = 7.334, 95% CI: 2.355-25.963). Obesity was also a significant risk factor (aOR = 3.035, 95% CI: 1.326-7.035).
Conclusion
The most frequent cause of PCCRC across various patient populations and colonoscopy indications was a possible missed lesion. Factors such as patient obesity and undergoing colonoscopy for surveillance may increase the likelihood of PCCRC. These findings highlight the importance of physician awareness regarding PCCRC risks during colonoscopy.
References
1. Bretthauer M, Løberg M, Wieszczy P, et al. Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death. N Engl J Med. 2022;387(17):1547-1556.
2. Rutter MD, Beintaris I, Valori R, et al. World Endoscopy Organization Consensus Statements on Post-Colonoscopy and Post-Imaging Colorectal Cancer. Gastroenterology. 2018;155(3):909-925.e3.
3. Govindarajan A, Rabeneck L, Yun L, Tinmouth J, Paszat LF, Baxter NN. Population-based assessment of the outcomes in patients with postcolonoscopy colorectal cancers. Gut. 2016;65(6):971-976.
