Study supports 20-year interval for colonoscopy screening

Abstract

Patients with a negative colonoscopy result might not need to have another colonoscopy for 20 years or more, suggests a population-based, case–control study (Gut 2006; 55: 1145–50). Hermann Brenner and colleagues (German Cancer Research Centre, Heidelberg, Germany) compared the adjusted relative risks of colorectal cancer in 380 patients who had a previous negative colonoscopy with those in 485 control patients who had not undergone previous colonoscopy, according to time since colonoscopy. Patients with previous negative colonoscopy had a 74% lower risk of colorectal cancer than did those without previous colonoscopy (adjusted odds ratio 0·26; 95% CI 0·16–0·40). The risk remained low even when the colonoscopy had been done 20 or more years previously, Brenner and colleagues report. “These fi ndings should have an impact on future screening guidelines”, says Brenner. “There are virtually no data available on colorectal-cancer risk beyond 10 years after a negative screening colonoscopy, which has hindered recommendations of longer screening intervals.” According to John Marshall (Georgetown University, Washington, DC, USA), this study suggests that patients who have even one negative colonoscopy at some point in their lives have a low risk of developing colon cancer and that this conclusion seems justifi ed by the data. However, he cautions that only fi ve (1%) patients and 13 (3%) controls fell into the “over 20-year” category, on which researchers base part of their conclusions. “We must remember that the majority of patients diagnosed with colon cancer have later-stage disease, suggesting that we are failing to detect earlystage colon cancer in most patients”, says Marshall. “While one colonoscopy is better than none, one should not conclude from this study that one, and only one, colonoscopy will prevent colon-cancer deaths.”