Fig. 1
From: Effectiveness, benefit harm and cost effectiveness of colorectal cancer screening in Austria
Natural history, impact of screening, and surveillance of the CRC state-transition cohort model. Green arrows – detected, red arrows – progression, blue arrows – switching strategy if adenoma, advanced adenoma or cancer remain undetected or low risk adenoma are detected. UICC - Union for International Cancer Control classification, CRC - colorectal cancer. Regular: regular screening, 3 year: 3-yearly surveillance, 5 year: 5-yearly surveillance. Each bubble represents a health state. Each arrow represents possible transitions between health states, which may occur each year. All individuals start in the healthy state with regular screening. Over time, individuals can develop adenomas. Adenomas can be detected by screening and removed. As a consequence, individuals move back to the healthy state. If advanced adenomas are detected and removed, individuals move back to the healthy state, but with 3-yearly surveillance. If adenomas are not detected, they can progress to advanced adenomas and cancer. Any cancer may be diagnosed at any stage by symptoms or screening. Individuals with diagnosed cancer (symptoms or screening) move to the diagnosed health states where they receive treatment. Individuals with diagnosed CRC may die from CRC. Individuals in any health state may die from other causes according to the age- and sex-specific mortality in Austria. The blue area includes the health states for individuals participating in the regular screening program (according to the investigated screening strategy). The yellow area includes the health states for individuals participating in 3-yearly surveillance (after detection of an advanced adenoma). The brown area includes the health states of the 5-yearly-surveillance program (after detecting non-advanced or no adenoma in the 3-yearly surveillance screening). The health states in these paths are similar compared to the health states of individuals participating in the regular screening program. Only the intervals of screening are shorter compared to the regular screening. If non-advanced adenomas are detected in the regular screening (i.e., according to the screening strategy), individuals will continue with screening using colonoscopy independent from the originally evaluated screening test. Individuals with diagnosed CRC may die from CRC