Comparison Of Clinicopathological Features And Prognosis Between Intramucosal And Submucosal Early Gastric Cancer

ObjectiveEarly gastric cancer(EGC)refers to tumor confined to the mucosa(T1a)or submucosa(T1b).Currently,there are limited researches to explore the clinicopathological characteristics and prognostic between intramucosal early gastric cancer(T1a EGC)and submucosal early gastric cancer(T1b EGC).Thus,the present study aimed to examine the differences in terms of lymph node metastasis(LNM)and prognosis between two groups and to determine the relevant risk factors affecting LNM and prognosis,which provided the basis for optimal treatment and the postoperative follow up of EGC.MethodsWe retrospectively analyzed 3,488 patients with EGC who were collected in the Surveillance,Epidemiology,and End Results database from 2004 to 2015.All patients were diagnosed with EGC by surgical resection and histological confirmation.The patients were divided into 2 groups: T1 a EGC group and T1 b EGC group.The clinicopathological characteristics of patients were compared in two groups.The multivariate logistic regression was used to identify potential risk factors of LNM.The Kaplan-Meier method was used to compare 5-year survival rate in two groups.The multivariate Cox regression was performed to explore the risk factors for poor prognosis.To eliminate the difference in baseline characteristics,a 1:1 ratio Propensity Score Matching(PSM)was conducted between T1 a EGC and T1 b EGC.Results1.The population cohort consisted of 3488 patients with surgically resected EGC,including 1799 T1 a EGC(51.6%)and 1689 T1 b EGC(48.4%)individuals,in accordance with our predefined inclusion criteria.There were significant differences in terms of age,year of diagnosis,primary sites,histology,cell type,LNM,tumor size,the number of retrieved lymph nodes,and surgery in two groups(P<0.05 for all comparisons).The rate of LNM was 6.6% in EGC patients,including 2.4% in T1 a EGC and 11.1% in T1 b EGC,respectively.Others clinicopathological featuresshowed that T1 b EGC tended to be older age,larger tumor size,and poorer differentiated.2.In multivariate logistic regression,the results showed that T1 b EGC significantly increased risk of LNM compared with T1 a EGC(OR,3.63;95%CI,2.53–5.19).Besides,other variables such as older age,poorly differentiated/undifferentiated,larger tumor size,and more retrieved lymph nodes also increased the risk of LNM.3.We evaluated 5-year cancer-specific survival(CSS)and overall survival(OS)between two groups using Kaplan–Meier curves.Results showed that T1 a EGC had better 5-year CSS and OS compared with the T1 b EGC group.The total 5-year CSS of EGC patients were 86.2%,a five-year CSS for T1 a EGC was 90.6%,and that for T1 b EGC reached 81.4%.Then,the two groups were further stratified by LNM.In patients with EGC without LNM,T1 a EGC still had a better 5-year CSS than T1 b EGC(91.5% vs 84.1%),whereas no difference was observed after LNM occurred.4.In the multivariate Cox regression model,T1b(HR,1.50;95%CI,1.22-1.85)and LNM(HR,2.82;95%CI,2.20-3.62)were independent predictors of increased mortality.Other race(HR,0.68;95%CI,0.53-0.88)and the number of retrieved lymph nodes more than 15(HR,0.65;95%CI,0.52-0.81)were independent protective factors for improving CSS.The other variables of age,cell type,tumor size and surgical type were also independent prognosis factors for improving CSS.5.A 1:1 matching cohort analysis was performed using the PSM method,and1522 patients were respectively generated in two groups after matching.The association was explored between invasive depth and LNM using univariate logistic regression,and the result also indicated that invasion depth was associated with LNM presenting a positive correlation(OR,1.63;95%CI,1.11-2.41).Meanwhile,we also explored prognosis between T1 a EGC and T1 b EGC.The difference was still noted regarding 5-year OS and CSS in two groups(OS: 76.4% vs.70.1%;CSS: 89.9% vs.83.8%).Conclusion1.T1 a EGC and T1 b EGC had different clinicopathological characteristics and prognosis.Patients with T1 b EGC tended to be older age,larger tumor size,poorer differentiated,and higher rate of LNM.Moreover,T1 a EGC group had a better 5-year survival rate than T1 b EGC group.2.LNM was the most important consideration factor when deciding on treatment strategy for EGC.The rate of LNM was 6.6% in EGC patients,of which the rate of LNM was 2.4% in T1 a,while it was significantly increased to 11.1% when invaded T1 b.The risk factors of affecting LNM included age,invasion depth,cell type and tumor size.3.Endoscopic treatment may be applied to T1 a EGC patients with low rate of LNM,whereas the high rate of LNM in most patients with T1 b EGC may require radical surgical resection with lymph node dissection.It should closely follow up regardless of endoscopic resection or surgery.The study provides more basis for the selection of treatment options,whether additional surgery after endoscopic treatment and the postoperative follow up of EGC patients.