Comparing The Differences Of Prognosis Evaluation Between The 7^th And 8^th Edition Of UICC/AJCC TNM Staging System For Gastric Carcinoma

Background: Recently,the 8^th edition of the American Joint Committee on Cancer（AJCC）TNM system was published,including several changes to the 7^th edition.Our aim was to compare the N staging between the old and new TNM classifications,and assess the availability of the new staging system used to evaluate Chinese patients at each stage of gastric cancer（GC）.Methods: The study retrospectively reviewed a database of patients diagnosed with GC and who underwent R0 resection between January 2005 and December 2012.Of them,1297 were included.The overall survival（OS）rates and classifications between the 7^th and 8^th edition TNM staging system were compared.Results: The major change to the 8^th edition involved stage III.The 8^th edition stratified pN3 into pN3 a and pN3b（5-year OS,27.9% versus 9.2%,p<0.001）,classified T4 a N2,T4 a N3a,and T4 a N3b into IIIA,IIIB,and IIIC（5-year OS,33.7% versus 26.1% versus 8.3%）,which were subclassified to stage IIIB and IIIC in the 7^th edition).The 5-year OS of IA,IB,IIA,IIB,IIIA,IIIB,and IIIC for the 7^th edition was 91.8%,82.4%,70.6%,63.2%,48.3%,25.0%,and 17.2%,respectively.Significant differences in the 5-year survival curves were found in the following: IA vs IB,p=0.031;IIA vs IIB,p=0.046;IIB vs IIIA,p=0.001;IIIA vs IIIB,p<0.001;IIIB vs IIIC,p=0.004.No significant difference was seen between IB and IIA,p=0.052.The 5-year OS of IA,IB,IIA,IIB,IIIA,IIIB,and IIIC for the 8^th edition was 91.8%,82.4%,71.3%,63.2%,44.0%,25.5%,and 8.8%,respectively.Significant differences in the 5-year survival curves were found in the following: IA vs IB,p=0.031;IIA vs IIB,p=0.046;IIB vs IIIA,p<0.001;IIIA vs IIIB,p<0.001;IIIB vs IIIC,p<0.001.No significant difference was seen between IB and IIA,p=0.052.The 8^th edition of the AJCC TNM system had a larger C-index value and a smaller AIC value,making it a more precise TNM staging system than the 7^th edition.Conclusions:So dividing pN3 classifacation of the 7^th edition into pN3 a and pN3 b classifacations of the 8^th edition is accurate.Hence,the 8^th edition is more suitable than the 7^th edition for evaluating the prognosis for patients with GC.