Early experience of three dimensional transrectal ultrasonography: comparison of diagnostic accuracy between two dimensional transrectal ultrasonography, computed tomography and magnetic resonance imaging in rectal cancer patients with preoperative chemoradiation therapy.

Purpose : This study was designed to evaluate the accuracy of three dimensional transrectal ultrasonography (3D TRUS) when compared to those of two dimensional transrectal ultrasonography, CT and MRI for preoperative chemoradiated rectal cancer. Material and methods : Ninety-nine rectal cancer patients were enrolled. Among them, 58 patients were staged by 2D TRUS, CT and MRI and 41 patients were staged by 3D TRUS, CT and MRI. Depth of tumor invasion (T) and nodal involvement (N) assessed by imaging modalities were compared with pathologic results. Results : When assessing depth of invasion, the accuracy of 2D and 3D TRUS,CT and MRI was 68.9%, 76%,68.6%, and 84.3%, respectively. Overstaging rates were 24.1%, 20%, 21.6%, and 9.6%, and understaging rates were 6.8%, 4%, 9.6% and 6%, respectively. In patients undergoing preoperative chemoradiation, accuracy of depth of invasion was 57.1%, 66.6%, 56.3%, and 62.5%, and overstaging rates were 28.5%,33.3%,43.7%, and 37.5%, and understaging rates were 14.2%,0%,0%, and 0%, respectively. When assessing nodal involvement, accuracy of 2D and 3D TRUS, CT and MRI was 58.62%, 64%, 67.47%, and 73.49%, respectively. In patients undergoing preoperative chemoradiation, accuracy of nodal involvement was 57.1%, 55.5%, 68.75%, and 68.7%, respectively. Conclusion : Although early experience, overall diagnostic accuracy of 3D TRUS was superior to conventional 2D TRUS. As accumulation of experiences, 3D TRUS as well as MRI could be used as a useful tool for preoperative imaging for rectal cancer.ope