S861 The Differences in the Clinicopathological Features of Early-Stage Adenocarcinomas of the Esophagogastric Junction Between the United States and Japan

Introduction: The incidence of adenocarcinomas of the esophagogastric junction (EGJ) has been increasing in both the United States and Japan. To better understand the pathogenesis of EGJ adenocarcinomas in these 2 populations, we compared early-stage tumors between American and Japanese patients. Methods: Internal review board-approved analysis of clinicopathological features of 42 American patients (AP) (43 lesions) and 93 Japanese patients (JP) (93 lesions) with Siewert type 1 or 2 and Vienna pathologic diagnosis 4 or 5 treated by endoscopic resection. Statistical differences between both cohorts were defined as P < 0.05. Results: No significant differences were found in median age in years (68 years [34-86] vs 72 years [39-85]) and male-to-female ratio (34:8 vs 80:13) for AP and JP. Tumor location (confined within the esophagus/involving the EGJ/confined within the stomach) was found in 21/21/1 in AP vs 20/36/37 in JP, with gastric location more frequent in JP (P < 0.01). After excluding tumors confined within the stomach, there were no significant differences in the mean tumor size (19.6 ± 9.32 mm vs 20 mm ± 10.1 mm) and depth of invasion (mucosa/submucosa: 27/15 vs 43/13) between AP and JP. The distribution of elevated/flat/depressed types was found in 35/7/0 in AP vs 31/6/19 in JP (P < 0.01), with depressed lesions occurring exclusively in JP. Well or high-grade dysplasia/moderately/poorly differentiated/other tumor types were found in 24/14/4/0 in AP vs 48/4/1/3 in JP (P < 0.01). Among tumors with submucosal invasion, histologic types in submucosal areas showed a trend toward significance (1/9/3/0 in AP vs 6/5/1/0 in JP) (P = 0.05). The length of columnar-lined esophagus also differed: long/short/none 18/16/7 in AP vs 12/37/7 in JP (P = 0.03). While long-segment was more common in AP, JP showed higher Prague C&M values (1.5 ± 2.0/4.7 ± 1.7 in AP vs 4.7 ± 5.0/8.0 ± 5.3 in JP) (P = 0.02). Intestinal metaplasia showed a trend toward higher prevalence in AP: 30/12 positive/negative in AP vs 29/27 in JP (P = 0.06). Tumor extension under squamous epithelium was more common in AP (35/6 positive/negative in AP vs 19/30 in JP) (P < 0.01). Positive horizontal margins occurred exclusively in AP (33/9/0 positive/negative/unknown in AP vs 0/54/2 in JP) (P < 0.01). Conclusion: This analysis revealed significant differences in macroscopic types, tumor grade and background mucosa between AP and JP with early-stage EGJ adenocarcinomas. These findings suggest distinct pathways of carcinogenesis.