Efficacy Of Radiotherapy Combined With Surgery For Locally Advanced Rectal Mucinous Adenocarcinoma:a Retrospective Study Of Surveillance,epidemiology,and End Results Population-based Data

Objective: To explore the efficacy of radiotherapy combined with surgery for locally advanced rectal mucinous adenocarcinoma.Methods: The SEER*Stat software was used to identify patients whose pathological diagnosis as locally advanced rectal mucinous adenocarcinoma from 1992 to 2013.All the 2149 patients were divided into three subgroups according to different therapeutic strategies,including surgery alone(S)and surgery combined with preoperative radiotherapy(RT+S)and surgery combined with postoperative radiotherapy(S+RT).Comparisons of count data were done using chi-square test.The Kaplan-Meier was used to draw the survival curve and assess survival rate.The Log-rank test was used to compare survival.According to gender,year of diagnosis,age at diagnosis,race,histopathologic grading,pathological TMN stage,depth of invasion,propensity score matching(PSM)was performed by R plug-in(version 2.8.1),making the baseline information of subgroups comparable.Cox multivariate regression analysis were applied to evaluate the prognostic factors.Results:(1)The constituent ratio of patients with different therapeutic strategies varies with the year of diagnosis:The therapeutic strategies for locally advanced rectal mucinous adenocarcinoma varies with the year of diagnosis.The incresing trend of group RT+S was observed from 1992 to 2013,while group S and S+RT were gradually decreasing from 1992 to 2013.(2)Comparison on the overall survival(OS)and the cancer specific survival(CSS):The mean median survival time of group S,RT+S and S+RT was 39,85 and 74 months respectively.The 5-year OS in group S was lower than that in group RT+S(38.7% vs 56.5%,P<0.001)and S+RT(38.7% vs55.2%,P<0.001),while group RT+S and S+RT were close in 5-year OS(56.5%比55.2%,P=0.166).In 5-year CSS,group S was lower than that of group RT+S(53.7% vs 62.2%,P<0.001)and S+RT(53.7% vs 60.7%,P=0.017),while group RT+S and S+RT were close(62.2%比 60.7%,P=0.392).(3)After the baseline information of subgroups was corrected through PSM: Compared with the group RT+S and S+RT,group S was still lower in 5-year OS and CSS(40.1% vs 54.5%,P<0.001;54.3% vs 63.3%,P=0.023),while group RT+S and S+RT were close in those two factors(55.5% vs 51.7%,P=0.789;57.7% vs60.5%,P=0.484).(4)The multi-factor analysis results showed: The year of diagnosis,histopathologic grading,age at diagnosis,radiotherapy,pathological TNM staging were the independent prognosis factors influencing the OS and CSS of the locally advanced rectal mucinous adenocarcinoma(P<0.001).Conclusion:(1)Comparing with surgery alone,surgery combined with pre/post-operative radiotherapy has benefited the locally advanced rectal mucinous adenocarcinoma.(2)The year of diagnosis,histopathologic grading,age at diagnosis,radiotherapy,pathological TNM staging were the independent prognosis factors influencing the OS and CSS of the locally advanced rectal mucinous adenocarcinoma.