Progression Rates of Colorectal Cancer by Dukes' Stage in a High‐Risk Group: Analysis of Selective Colorectal Cancer Screening

PURPOSEThe progression rates of colorectal cancer by Dukes' stage in a high-risk group were estimated and applied to evaluate the efficacy of different screening regimens. PATIENTS AND METHODSOf 6303 high-risk subjects invited to a colorectal cancer screening project with colonoscopy, 39 screen-detected cases and 16 postscreening cases were diagnosed with information available on Dukes' stage. A five-state Markov process was applied to estimate parameters pertaining to the disease natural history of colorectal cancer by Dukes' stage. RESULTSThe estimates of the mean sojourn time in years were 3.10 for preclinical Dukes' A and B and 1.92 for preclinical Dukes' stages C and D. The predicted reductions of Dukes' stages C and D achieved by annual, blennial, 3-yearly, and 6-yearly screening regimens against the control group were 60%, 49%, 40%, and 25%, respectively. These, in turn, yield the corresponding predicted mortality reductions of 39%, 33%, 28%, and 18%. CONCLUSIONSThese findings suggest that to achieve a 30% mortality reduction, as observed in annual fecal occult blood testing, a prudent interscreening interval with colonoscopy for this high-risk group should not be longer than 3 years.