Clinical Efficacy Of Radiotherapy Combined With Surgery For Locally Advanced Gastric Signet-Ring-Cell Carcinoma:A SEER Database Analysis

Objective To analyze the risk factors affecting the prognosis of locally advanced(stage II and III)gastric signet ring cell carcinoma(GSCC),and to determine whether radiotherapy has potential benefits for patients with locally advanced gastric signet ring cell carcinoma undergoing surgery.And provide a scientific basis for the treatment of patients with locally advanced signet ring cell carcinoma in the future.Methods Clinical data of patients with locally advanced gastric signet-ring-cell carcinoma diagnosed by postoperative pathology from 2000-2016 were collected from the US Surveillance,Epidemiology,and End Results(SEER)database.All the enrolled patients were divided into three groups according to different treatments,including surgery alone(SA)group,preoperative radiotherapy(RT+S)group,postoperative radiotherapy(S+RT)group.The extracted data including basic data of patients and tumor,treatment status,and follow-up results.The χ2 test was used to compare the count data.Kaplan-Meier method was used to draw the survival curve and calculate the survival rate.The survival was analyzed and compared by Log-rank test.The R language 3.6.1 was used to match the patients as 1:1 pairing through the propensity score matching(PSM).The matching variables including gender,age,race,tissue differentiation,TNM stage,depth of invasion,tumor size,making the baseline data comparable in each subgroup.The Cox proportional hazard model was used for multivariate analysis of prognostic factors.Results A total of 1413 patients with locally advanced gastric signet-ring-cell carcinoma were enrolled in the study.Univariate analysis showed that age,AJCC stage,T stage,combined radiotherapy or not,tumor size were correlated with prognosis.Cox proportional model analysis showed that age,AJCC stage,tumor size,whether combined with radiotherapy were independent risk factors for prognosis.There were 727 patients in the SA group,138 patients in the RT+S group while 548 patients in the S+RT group.The median overall survival time in each group were 19 months in the SA group,26 months in the RT+S group,33 months in the S+RT group;the 5-year overall survival(OS)rate was 19.5%,26.9%,34.0% respectively;the median cancer-specific(CSS)survival time was 29,31,43 months respectively;the 5-year CSS rate were 32,4%,35.3% 43.6% respectively.In comparison among 3 groups,the 5-year OS rate was significantly lower in the SA group than in the RT+S and S+RT group(all P<0.05);the 5-year CSS rate was lower in the SA group than in the S+RT group(P<0.0001),while not significantly different between the SA vs RT+S groups.The 5-year OS and CSS were not significantly different between the RT+S and S+RT groups(5y-OS:21.1vs34.0,P<0.0001;5yCSS:32.1%vs43.6%,P<0.0001).Cox multivariate analysis showed that radiotherapy(HR:0.799,95%CI:0.745～0.857,P<0.0001)was an independent prognostic factor for OS and CSS of locally advanced gastric signet-ring-cell carcinoma.Conclusion Age,AJCC stage,tumor size and combination of radiotherapy are important prognostic factors for locally advanced gastric signet ring cell carcinoma.Preoperative and postoperative radiotherapy can improve the overall survival rate of patients with locally advanced gastric signet ring cell carcinoma.Postoperative radiotherapy can also improve the tumor specific survival rate of patients with locally advanced gastric signet ring cell carcinoma,and benefit the long-term prognosis of patients.