The New American Joint Committee on Cancer T Staging System for Stomach: Increased Complexity without Clear Improvement in Predictive Accuracy for Endoscopic Ultrasound

Abstract Background: The efficacy of endoscopic ultrasound (EUS) for determining T category is variable for gastric cancer. The aim of this study is to evaluate the superiority of EUS by using the 6th edition American Joint Committee on Cancer (AJCC) staging system for stomach cancer compared to the new 7th/8th edition.Methods: A retrospective analysis of clinical and EUS imaging features of 348 gastric carcinoma patients who underwent radical resection were collected. Differences between the 6th edition and 7th/8th edition T staging system for EUS preoperative evaluated were compared.Results: The accuracy of EUS T staging was 72.4% for 7th/8th edition and 78.4% for 6th edition; especially the T3 stage accuracy was significantly worse when T3 group status was changed. The tumor location, EUS type and histological type were associated with inaccuracy. We further analyzed the EUS image features for each tumor T stage and found muscularis propria (MP) visible indistinctly or obvious thickening were considered to be indicators that lesions involved to the MP with a sensitivity of 81.3%; MP disappeared completely and accompanied with serosal layer intact might be a marker that lesion invaded to the subserosa; We also found that irregularities in the outer edge of the gastric wall were markers of gastric serosal layer penetration with a positive predictive value of 92.2%.Conclusions: The increased complexity of the 7th/8th edition T staging system is accompanied by worsening in the predictive accuracy for EUS as compared to the 6th edition. Furthermore, the tumor location, EUS type, histological type and EUS image features for each tumor T stage should warrant attention.