The impact of colorectal cancer screening on life expectancy

Methods: The purpose of this study was to assess the effect of screening fo r colorectal cancer on life expectancy and estimate the number of colonosco pies needed per life year saved. The declining exponential approximation of life expectancy was used to calculate the effect of colorectal cancer scre ening on expected remaining lifetime, The annual number of deaths from colo rectal cancer and the size of the population were obtained from the vital s tatistics of the United States. Published reports were consulted to determi ne the decrease in mortality from colorectal cancer achieved by fecal occul t blood testing, screening sigmoidoscopy or colonoscopy, A Markov chain ana lysis was used to determine the endoscopic resources required to screen and survey the entire population of U.S. residents age 50 years until death or age 85 years. Results: Colorectal cancer decreases the life expectancy of U.S. residents aged 50 to 54 years by 292 days and those aged 70 to 74 years by 70 days. S creening with fecal occult blood tests extends expected lifetime of the 2 a ge groups by 51 and 12 days, respectively, whereas screening with sigmoidos copy leads to increases of 86 and 21 days. Colonoscopic screening increases expected lifetime by 170 and 41 days, respectively. The number of colonosc opies needed to save 1 year of expected life ranges from 2.9 to 6.0, depend ing on the type of screening regimen used. Conclusions: The extension of life through screening colonoscopy is two or three times longer than the extension achieved through flexible sigmoidosco py or fecal occult blood test, respectively. Although a large number of col onoscopies are required to screen the U.S. population, relatively few colon oscopies need to be invested per year of life expectancy saved.