Subjects with negative colonoscopy findings might not need to undergo repeat screening for at least 20 years, if at all, because of the very low risk of cancer.

“Screening colonoscopy is thought to be a powerful and cost-effective tool to reduce colorectal cancer incidence and mortality. Whether and when colonoscopy with negative findings has to be repeated is not well defined,” scientists in Germany reported.

“The aim of this study was to assess the long term risk of clinically manifest colorectal cancer among subjects with negative findings at colonoscopy,” explained H. Brenner and colleagues, German Cancer Research Center. “Three hundred and eighty cases and 485 controls participating in a population based case-control study in Germany.

“Detailed history and results of previous colonoscopies were obtained by interview and from medical records. Adjusted relative risks of colorectal cancer among subjects with a previous negative colonoscopy compared with those without previous colonoscopy were estimated according to time since colonoscopy.”

“Subjects with previous negative colonoscopy had a 74% lower risk of colorectal cancer than those without previous colonoscopy (adjusted odds ratio (aOR)=0.26 (95% confidence interval, 0.16 to 0.40)). This low risk was seen even if the colonoscopy had been done up to 20 or more years previously. Particularly low risks were seen for sigma cancer (aOR=0.13 (0.04 to 0.43)) and for rectal cancer (aOR=0.19 (0.09 to 0.39)), and after a negative screening colonoscopy at ages 55 to 64 [aOR=0.17 (0.08 to 0.39)] and older [aOR=0.21 (0.10 to 0.41)].

“Subjects with negative findings at colonoscopy are at very low risk of colorectal cancer and might not need to undergo repeat colonoscopy for 20 years or more, if at all,” indicated the investigators.

The researchers concluded, “The possibility of extending screening intervals to 20 years or more might reduce complications and increase the feasibility and cost-effectiveness of colonoscopy based screening programmes.”

Brenner and colleagues published their study in Gut (Does a negative screening colonoscopy ever need to be repeated? Gut, 2006;55(8):1145-1150).

For more information, contact H. Brenner, German Cancer Research Center, Division Clinic Epidemiology & Aging Research, Bergheimer Str 20, D-69115 Heidelberg, Germany.

Publisher contact information for the journal Gut is: B M J Publishing Group, British Med Association House, Tavistock Square, London WC1H 9JR, England.