Brenner and colleagues1 conducted a cross-sectional study of 3,287 participants of screening colonoscopy aged = 55 years from the state of Saarland, Germany, between May 2005 and December 2007. Previous colonoscopy history was obtained by standardized questionnaire, and its association with prevalence of advanced colorectal cancer (CRC) was estimated.

The prevalence of left-sided advanced CRC was lower in participants who had received a colonoscopy in the preceding 10 years. The participants were screened in community settings. Although colonoscopy is used for early detection and prevention of CRC, data are sparse on protection from colorectal cancer overall and by anatomical site of colonoscopy performed in the community setting. No decrease was found in right-sided advanced CRC, according to a new study published in the Journal of the National Cancer Institute.1

Advanced CRC was detected in 308 (11.4%) of the 2,701 participants with no previous colonoscopy compared with 36 (6.1%) of the 586 participants who had undergone colonoscopy within the preceding 10 years. Prevalence of left-sided advanced CRC, but not right-sided advanced CRC was substantially lower within a 10-year period after colonoscopy in this community setting.

The authors concluded that their results add to the evidence that the protective effect is much stronger in, if not confined to, the left colon and rectum, at least in the community setting.1 Limitations of the study include:  

1. Colonoscopy histories were self-reported
2. Colonoscopies were performed in the community setting by many endoscopists
3. Histopathologic examination was performed by various pathology laboratories
4. The numbers of advanced neoplasms at specific sites were rather small

This study is an important contribution to the growing body of literature of colonoscopy effectiveness research, but more research is needed. In an accompanying editorial, Baxter & Rabeneck2 raise important questions about the incremental benefits of screening colonoscopy, stating, "As more observational evidence accumulates, the answer to this question becomes less certain." 2

References

1. Brenner H, Hoffmeister M, Arndt V, et al. Protection From Right- and Left-Sided Colorectal Neoplasms After Colonoscopy: Population-Based Study. J Natl Cancer Inst. 2010;102:89-95;doi:10.1093/jnci/djp436  Link to abstract http://jnci.oxfordjournals.org/cgi/content/abstract/djp436
2. Baxter NN, Rabeneck L. Is the Effectiveness of Colonoscopy “Good Enough” for Population-Based Screening? J Natl Cancer Inst. 2010;102:70-71; doi:10.1093/jnci/djp469 Link to free full text at http://jnci.oxfordjournals.org/cgi/reprint/102/2/70