Accuracy of preoperative CT for local staging in colorectal carcinomas

Introduction: This study aimed to determine the accuracy of computed tomography (CT) in the evaluation of local tumour invasion and regional lymphadenopathy in colorectal carcinomas. Methods: A total of 99 consecutive patients who had undergone a contrast-enhanced CT within two weeks prior to surgery with histopathological confirmation of colorectal carcinoma were selected. Intravenous contrast-enhanced CT was performed with a 5-7 mm collimation. Axial images were retrospectively and independently reviewed by two radiologists (R1 and R2) who were blinded to the surgical findings and histopathology. The readers assessed the primary tumour according to modified CT staging criteria. The radiological assessment was then compared with the surgical findings and histopathology for accuracy and inter-observer agreement. Results: At histopathology, the T-stage of the tumours was T2 in five, T3 in 62 and T4 in 32 patients, and the N-stage was N0 in 36, N1 in 28 and N2 in 35 patients. The accuracy of CT for T-stage and N-stage for the two readers was 45.5 percent and 60.6 percent (κ is 0.30) and 33.3 percent and 45.4 percent (κ is 0.23), respectively. The understaging and overstaging by R1 and R2 was 40.4 percent, 21.2 percent and 14.1 percent, 17.2 percent for T-stage and 22.2 percent, 37.4 percent and 32.3 percent, 28.3 percent for N-stage. The accuracy of serosal invasion for R1 and R2 (tumour perforates the visceral peritoneum or directly involves the adjacent organs) was 63.6 percent and 66.7 percent (κ is 0.51), respectively. The understaging and overstaging by R1 and R2 for serosal invasion was 24.1 percent, 12.1 percent and 20.1 percent, 12.1 percent, respectively. Conclusion: Our study results show that the accuracy for CT staging of colorectal carcinomas for T-stage and in particular, serosal invasion, is moderate, but it is relatively low for N-stage.