Peritoneal metastasis in gastric cancer with particular reference to lymphatic advancement; Extranodal invasion is a significant risk factor for peritoneal metastasis

Background and Objectives: We investigated the relationship between peritoneal metastasis and lymphatic involvement in gastric cancer by examining resected specimens. Methods: Twenty-seven consecutive gastric cancer patients who had synchronous peritoneal metastasis and 29 who developed metachronous peritoneal metastasis after surgery between 1985 and 1997 were included in this study. They were compared with 61 advanced gastric cancer (pT2 or more deeply into the gastric wall in the UICC-TNM) patients who had neither synchronous nor subsequent peritoneal metastasis, and who lived a disease-free course during 3 years. We compared the patients' clinicopathological features and in particular, the patterns of extranodal invasion in the resected lymph nodes. Results: Extranodal invasion with peritoneal metastasis was more common than extranodal invasion without peritoneal metastasis (P < 0.0001). Multivariate analysis revealed that the correlation between extranodal invasion and peritoneal metastasis was highly significant (P < 0.0001); the odds ratio was 18.894. Metastasis to the lymph nodes was the next most significant risk for peritoneal metastasis (P = 0.0043). Conclusions: We believe that the lymphatic system correlates closely with the establishment of peritoneal metastasis. J. Surg. Oncol. 2000;75:165-171. (C) 2000 Wiley-Liss, Inc.