The 8th edition of the American Joint Committee on Cancer tumor-node-metastasis staging system for gastric cancer is superior to the 7th edition: results from a Chinese mono-institutional study of 1663 patients

Abstract

Background: We investigated the superiority of the 8th edition of the tumor-node-metastasis (TNM) system for patients in China with gastric cancer.

Methods: The survival outcomes of 1663 patients with gastric cancer undergoing radical resection were analyzed.

Results: In the 8th edition system, homogeneous 5-year survival rates among different pathological TNM (pTNM) categories belonging to the same stage were observed. However, in the 7th edition system, the differences of 5-year survival rate among pTNM categories belonging to the same stage were observed in stages IIB (P = 0.010), IIIB (P = 0.004), and IIIC (P < 0.001). For patients in the pT1-3 (P < 0.001) and pT4a (P < 0.001) categories, there were significant differences in survival between patients in the pN3a and pN3b categories. Furthermore, partial cases (pT4bN0M0/T4aN2M0) of stage IIIB were downstaged to stage IIIA in the 8th edition system, and the 5-year survival rate of these patients was significantly better than that of patients in stage IIIB in the 8th edition system. Similarly, the 5-year survival rate of patients in p4bN2M0/T4aN3aM0 downstaged from stage IIIC to IIIB was significantly better than that of patients in stage IIIC. Compared with the 7th edition system, the 8th edition system had a higher likelihood ratio and linear trend chi-squared score and a smaller Akaike information criteria value.

Conclusions: The 8th edition system is superior to the 7th edition system in terms of homogeneity, discriminatory ability, and monotonicity of gradients for Chinese patients with gastric cancer.

Keywords: Chinese patients; Gastric cancer; Staging system; Survival outcome.

Fig. 1

Flowchart of patient selection process in this study

Fig. 2

Stage-related 5-year survival rates in the 7th and 8th edition staging systems. Significant differences were observed among all stages, with the exception of stages IB and IIA (P = 0.131) in both 7th and 8th edition staging systems. a The 5-year survival rates based on the 8th edition staging system were as follows: IA: 94.5%; IB: 88.4%; IIA: 78.0%; IIB: 70.6%; IIIA: 53.8%; IIIB: 33.3%; IIIC: 18.7%. Significant differences in 5-year survival rate were observed between stages IA versus IB (P = 0.027), IIA versus IIB (P = 0.046), IIB versus IIIA (P = 0.001), IIIA versus IIIB (P < 0.001), and IIIB versus IIIC (P < 0.001). b The 5-year survival rates based on the 7th edition staging system were as follows: IA: 94.5%; IB: 88.4%; IIA: 78.0%; IIB: 70.3%; IIIA: 57.6%; IIIB: 49.2%; IIIC: 27.6%. Similarly, significant differences in 5-year survival rate were observed between the stages of IA versus IB (P = 0.027), IIA versus IIB (P = 0.045), IIB versus IIIA (P = 0.033), IIIA versus IIIB (P = 0.042), and IIIB versus IIIC (P < 0.001)

Fig. 3

Comparisons of 5-year survival rates between patients in the pN3a and pN3b categories in the 8th edition staging system. a The 5-year survival rate of patients in the 8th edition pT1-3N3aM0 was significantly better than that of patients in pT1-3N3bM0 (60.0% vs. 0.0%, P < 0.001). b A significant difference in 5-year survival rate was also observed between pT4aN3aM0 and pT4aN3bM0 in the 8th edition TNM system (32.8 vs. 17.4%, P < 0.001)

Fig. 4

Comparisons of 5-year survival rates between patients downstaged into different stages and those in the former stages in the 8th edition staging system. a The 5-year survival rate of patients in the 8th edition pT4bN0M0/T4aN2M0 downstaged from IIIB into IIIA was significantly better than that of patients in stage IIIB (44.5 vs. 28.4%, P < 0.001). b The 5-year survival rate of patients in the 8th edition pT4bN2M0/T4aN3aM0 downstaged from stage IIIC into IIIB was significantly better than that of patients in stage IIIC (28.0 vs. 15.1%, P < 0.001)