Incorporation of perigastric tumor deposits into the TNM staging system for primary gastric cancer

BACKGROUND: The current prognostic significance of perigastric tumor deposits (TDs) in gastric cancer (GC) remains unclear. AIM: To assess the prognostic value of perigastric TDs and put forward a new TNM staging framework involving TDs for primary GC. METHODS: This study retrospectively analyzed the pathological data of 6672 patients with GC who underwent gastrectomy or surgery for GC with other diseases from January 1, 2012 to December 31, 2017 at the Chinese PLA General Hospital. According to the presence of perigastric TDs or not, the patients were divided into TD-positive and TD-negative groups by using the method of propensity score matching. The differences between TD-positive and TD-negative patients were analyzed using binary logistic regression modeling. The Kaplan-Meier method was used to plot survival curves. Multivariate Cox regression modeling and the log-rank test were used to analyze the data. RESULTS: Perigastric TDs were found to be positive in 339 (5.09%) of the 6672 patients with GC, among whom 237 were men (69.91%) and 102 were women (30.09%) (2.32:1). The median age was 59 years (range, 27 to 78 years). Univariate and multivariate survival analyses indicated that TD-positive GC patients had a poorer prognosis than TD-negative patients (P < 0.05). The 1-, 3-, and 5-year overall survival rates of GC patients with TDs were 68.3%, 19.6%, and 11.2%, respectively, and these were significantly poorer than those without TDs of the same stages. There was significant variation in survival according to TD locations among the GC patients (P < 0.05). A new TNM staging framework for GC was formulated according to TD location. When TDs appear in the gastric body, the original stages T1, T2, and T3 are classified as T4a with the new framework, and the original stages T4a and T4b both are classified as T4b. When TDs appear in the lesser curvature, the previous stages N0, N1, N2, and N3 now both are classified as N3. When TDs appear in the greater curvature or the distant tissue, the patient should be categorized as having M1. With the new GC staging scheme including TDs, the survival curves of patients in the lower grade TNM stage with TDs were closer to those of patients in the higher grade TNM stage without TDs. CONCLUSION: TDs are a poor prognostic factor for patients with primary GC. The location of TDs is associated with the prognosis of patients with primary GC. Accordingly, we developed a new TNM staging framework involving TDs that is more appropriate for patients with primary GC.