Direct Comparison of an Optical Colonoscopy and Virtual Colonoscopy Colorectal Cancer Screening Program in the Average Risk Patient Richard Hsu, Deepak Gopal, Mark Reichelderfer, Darren C. Schwartz, David H. Kim, Perry J. Pickhardt, Andrew J. Taylor, Patrick R. Pfau Background: Virtual Colonoscopy (VC), also known as CT Colonography is a new technology that has not been directly compared in practice to standard colorectal cancer (CRC) screening with optical colonoscopy (OC). Aim: To compare the findings of CRC screening in an average risk population between a third party covered VC program and a screening program using OC. Methods: VC CRC screening for patients with no increased risk of colon cancer is provided at our institution covered by third party payers. On VC screening tests at our program polyps ! or Z 5 mm are not reported, patients with polyps 6-9 mm are offered VC surveillance vs. colonoscopic polypectomy, and polyps O or Z 10 mm are referred for polypectomy. OC screening is performed with removal or ablation of all polyps regardless of size. Results of polyp findings in patients 50 years old or greater and having an average risk of CRC were compared between OC and VC on a per patient basis. Results: 1110 patients were screened with VC (4/04-4/05), 1132 with OC (1/05-5/05), mean age 56.1 yrs both groups. 933 total polyps were seen on OC, 255 of which were recovered adenomas. 153 total polyps were seen on VC, 61 recovered adenomas with 50 patients in VC surveillance. OC identified a significantly greater number of patients with polyps (443, 39.1%) than VC (120, 10.8%), p ! 0.0001). There was no difference between OC (32, 2.8%) and VC (43, 3.9%) in the identification of patients with polyps O 10 mm, (p Z 0.17). OC (132, 11.7%) identified a significantly greater number of patients with medium sized polyps (6-9 mm) than VC (77, 6.9%), (p ! 0.0001). OC identified 362 patients (32.0%) with polyps ! or Z 5 mm; this size polyp was not identified/reported on VC per protocol. OC screening led to a significantly greater number of patients with known adenomas removed than VC (187, 16.5%) vs. (48, 4.3%), (p ! 0.0001) with 50 patients (4.5%) undergoing VC surveillance. An identical number of advanced adenomas (O Z 10 mm or advanced histology) were resected by OC (31, 2.7%) and VC (31, 2.8%). There was no significant difference in complication rate between the OC screening program (7, .6%) and the VC program (3, .3%), (p Z .15). All complications were related to OC procedure. Conclusions: 1) OC and VC screening programs will identify an equal number of patients with large polyps and advanced adenomas. 2) OC colorectal cancer screening will identify a significantly greater number of patients with medium and small polyps and adenomas than VC. 3) The importance and behavior of polyps !10 mm needs to be further determined and studied as VC screening and surveillance programs are instituted into practice.