Preoperative Lymph Node Staging of Advanced Gastric Cancer with Helical CT: Assessment of New TNMClassification

ABSTRACT

PURPOSE: To evaluate preoperative N staging of advanced gastric cancer(AGC) using helical CT according to thenew TNM classification. MATERIALS AND METHODS: Helical CT findings of AGCs in N staging were prospectivelyevaluated and correlated with pathologic staging in 60 patients with AGCs who underwent surgery. In all patients,contrast-enhanced helical CT with 5 -7 mm silce thickness and 5 -7 mm reconstruction was performed after ingestionof 600 - 800ml of water. A total of 150ml of contrast medium was administered intravenously at a rate of 4mL/secand CT scans were obtained 60 seconds after the initiation of intravenous administration of contrast medium. CTnodal status was assessed according to the 1997 UICC/AJCC N staging system as N0, no lymph node metasta-sis; N1,1 -6 metastatic regional lymph nodes; N2, 7 -15 metastatic regional lymph nodes; N3, more than 15 metastaticregional lymph nodes. Lymph nodes at least 5mm in short-axis diameter or more than three lymph nodes in a focalarea (clustered appearance) regardless of size were interpretated as positive for metastasis. RESULTS: Of thetotal 1,334 lymph nodes dissected, 352(26%) were positive for metastasis. The sensitivity of helical CT scans in Nstaging of AGCs was 61%, specificity was 36 %, and overall accuracy was 55% (33 of 60cases), Nine(15 %) cases wereoverstaged and 18(30 %) were understaged. CONCLUSION: Our results indicate that the results of helical CT inpreoperative N staging of AGCs according to the new TNM classification showed no improvement despite theapplication of favorable criteria for lymph node metastasis. Further evaluation using various analytic approachesis necessary.