Extranodal soft tissue metastasis as an independent prognostic factor in gastric cancer patients aged under 70 years after curative gastrectomy

BACKGROUND: Accumulating evidence confirms the potential prognostic value of extranodal soft tissue metastasis (ESTM) in patients with solid cancers. The aim of this study was to elucidate the potential relationship between ESTM and lymph node (LN) metastasis, demonstrate clinicopathological predictive prognostic factors for ESTM and LN metastasis, and identify the prognostic value of ESTM for gastric cancer (GC) patients aged under 70 years. METHODS: A total of 580 GC patients who underwent the curative resection between 2003 and 2011 were included to identify if ESTM is essential to improve the accuracy of prognostic evaluation of the GC patients postoperatively. Overall survival rates were tested by Kaplan-Meier analysis. Univariate and multivariate analyses were applied to clarify the independent prognostic factors. Logistic regression analysis was adopted to clarify the risk factors for evaluating the presence of ESTM and LN metastasis. After cut-point survival analysis, the GC patients were divided into three subgroups based on the number of ESTM and then incorporated into the pTNM stage of gastric carcinoma to identify the possibility and necessity of incorporating ESTM into staging. RESULTS: ESTM was associated with advanced pT, pN and pTNM categories, large tumour size and the presence of signet-ring cell (SRC) variants. Survival analyses revealed that ESTM was associated with the OS and was an independent prognostic predictor in this GC patient cohort. Logistic regression analysis proved that ESTM and pT stage are significantly correlated with LN metastasis. Additionally, the ESTM was incorporated into the eighth edition of the pTNM classification and the prognostic evaluation of pTNME classification were calculated directly, and the results indicated that ESTM can reduce the stage migration. CONCLUSIONS: ESTM is a significant independent predictor of survival in GC patients. To achieve R0 surgery, lymph nodes, soft tissues, fascia and adipose tissue should be resected en bloc at the same time as lymph node dissection. ESTM should be incorporated into pTNM staging according to the number retrieved from postoperative samples.