On Jun. 5, 2003, data from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial gave fresh insight into the appropriate screening intervals for colorectal cancer after a negative exam. This was the largest study to date of repeat sigmoidoscopy screening after an exam.

In 2003, the accepted interval for sigmoidoscopy, a technique in which the rectum and lower colon were examined with a lighted instrument called a sigmoidoscope, was 5 years after a negative exam. This recommendation was based primarily on indirect evidence.

Exactly how often to repeat sigmoidoscopy is an evolving field of research. It was unclear whether data from this study, which measured the incidence of growths or polyps 3 years after an initial exam, might play a role in changing the recommended 5-year interval.