The Usefulness of Transrectal Ultrasonography for Preoperatively Staging Rectal Cancer

ABSTRACT

PURPOSE: The preoperative assessments of the depth of invasion in the rectal wall and the presence of lymph node metastasis are very important in determining the proper treatment modality for rectal cancer. The purpose of this study is to evaluate the accuracy of transrectal ultrasonography (TRUS) for preoperatively staging rectal cancer, as compared with computerized tomography (CT). METHODS: 62 patients who were diagnosed with rectal cancer were staged by using TRUS and CT, preoperatively. The ultrasnonographic tumor stage (uT), the US nodal stage (uN) and the computerized tomographic tumor stage (cT) and the CT nodal (cN) stage were investigated. The accuracy, sensitivity, specificity, PPV (Positive predictive value) and NPV (Negative predictive value) were calculated and compared with the pathologic staging. RESULTS: The accuracies of TRUS and CT in assessing the depth of rectal wall invasion were 82.2% and 79.0%, respectively. The sensitivity, specificity, PPV and NPV of TRUS were 68.1%, 81.9%, 70.4% and 85.4% and those of CT were 53.2%, 78.9%, 73.7% and 80.7%, respectively. The sensitivity of T1 was 77.8% with using TRUS and 33.3% with using CT, respectively. The incidence of over- and under-staging was 17.8% and 9.7% with using TRUS and 25.8% and 6.5% with using CT, respectively. The accuracies of TRUS and CT in assessing the involvement of lymph nodes were 62.4% and 68.8%, respectively. The incidence of over-staging for TRUS and CT was 41.9% and 21.0%, respectively. The incidence of under-staging for TRUS and CT was 20.1% and 25.8%, respectively. There was no meaningful factor influencing the accuracy of TRUS. CONCLUSION: TRUS is very useful tool for the preoperative assessment of the depth of rectal cancer invasion. However, the evaluation of lymph node involvement by TRUS has limitations.