Some guidelines have suggested that screening for colon cancer should stop after 75 years or 85 years at the latest. However recently, older adults who have never been screened for CRC (23 percent of US elderly individuals), one-time screening appears to be cost-effective up to age 86 years based on results of a recent study.  Colonoscopy was cost-effective to age 83 years, sigmoidoscopy to 84 years, and fecal tool blood testing up to 86 years for patients without comorbidity and at average risk for CRC.