Colonoscopy is the mainstay modality of choice in colorectal cancer screening worldwide. However, the rate of colonoscopy for colorectal cancer screening is very low (approximately 5-10%) because of the limited local medical resources (such as endoscopists and regional endoscope). This observational diagnostic test study aims to compare the diagnostic yield of routine computed tomography and colonoscopy in detecting colorectal tumors in patients at risk of colorectal cancer (aged more than 50 years and FIT+). The main question\[s\] it aims to answer are: 1. To compare the diagnostic yield between the routine computed tomography and colonoscopy. 2. To compare the procedure-related adverse events between the routine computed tomography and colonoscopy.