Differences and comparison of prognostic evaluation between AJCC staging system 7th edition and 8th edition for gastric cancer(A report of 1 383 cases)

Objective To compare the differences and clinical value of prognostic evaluation between American Joint Committee on Cancer (AJCC) TNM staging system 7th edition and 8th edition for gastric cancer (GC). Methods The retrospective case-control study was conducted. The clinicopathological data of 1 383 GC patients who were admitted to the First People′s Hospital of Changzhou between January 2008 and August 2012 were collected. Distal gastrectomy, proximal gastrectomy + pyloroplasty or total gastrectomy were performed according to preoperative evaluation and intraoperative exploration. Observation indicators: (1) surgical and postoperative situations; (2) follow-up and survival situations; (3) T staging comparison between AJCC TNM staging system 7th edition and 8th edition; (4) N staging comparison of AJCC TNM staging system 8th edition; (5) prognostic analysis in N staging of AJCC TNM staging system 8th edition; (6) TNM staging comparison between AJCC TNM staging system 7th edition and 8th edition; (7) prognostic analysis in different TNM staging between AJCC TNM staging system 7th edition and 8th edition. Follow-up using outpatient examination and telephone interview was performed to detect postoperative survival up to October 2017. Measurement data with normal distribution were represented as ±s. Measurement data with skewed distribution were described as M (range). The survival curve and survival rate were respectively drawn and calculated by the Kaplan-Meier method, and the Log-rank test was used for survival analysis. Results (1) Surgical and postoperative situations: 1 383 GC patients underwent successful radical gastrectomy, including 923 with distal gastrectomy, 165 with proximal gastrectomy and 295 with total gastrectomy. Of 1 383 patients, 115 with postoperative complications were improved by symptomatic treatment, including 87 with surgical complications and 28 with non-surgical complications. Postoperative pathological examinations: total number of intraoperative lymph node dissection and number of lymph node metastasis were 25±12 and 7±4; 577 didn′t have lymph node metastasis and 806 had regional lymph node metastasis; 308 were in early GC and 1 075 in advanced GC. (2) Follow-up and survival situations: 1 383 patients were followed up for 1-117 months, with a median time of 34 months. The 1-, 3- and 5-year survival rates of 1 383 patients were respectively 90.5%, 71.9% and 61.1%. (3) T staging comparison between AJCC TNM staging system 7th edition and 8th edition: T staging definition between AJCC TNM staging system 7th edition and 8th edition was identical. T staging of 1 383 patients: 308, 192, 65, 628 and 190 were respectively detected in T1, T2, T3, T4a and T4b stagings. (4) N staging comparison between AJCC TNM staging system 7th edition and 8th edition: N staging definition between AJCC TNM staging system 7th edition and 8th edition was identical. N staging of 1 383 patients: 577, 255, 207, 230 and 114 were respectively detected in N0, N1, N2, N3a and N3b stagings. N3a and N3b were classified as N3 staging of AJCC TNM staging system 7th edition, but they were classified as independent staging of AJCC TNM staging system 8th edition. (5) Prognostic analysis in N staging of AJCC TNM staging system 8th edition: 5-year survival rate of patients in N0, N1, N2, N3a and N3b stagings was respectively 85.6%, 76.5%, 59.4%, 45.2% and 32.5% based on AJCC TNM staging system 8th edition, with a statistically significant difference in survival (χ2=394.400, P 0.05), betweenⅡA andⅡB stagings (χ2=0.265, P>0.05), and between ⅢB and ⅢC stagings (χ2=1.550, P>0.05). According to 8th edition, cases and 5-year survival rate were respectively 247, 89.5% in ⅠA staging and 147, 83.7% inⅠB staging and 77, 75.9% in ⅡA staging and 205, 70.7% in ⅡB staging and 288, 53.8% in ⅢA staging and 258, 37.3% in ⅢB staging and 161, 28.5% in ⅢC staging, with a statistically significant difference in survival among sub-stagings (χ2=234.900, P 0.05) and betweenⅡA andⅡB stagings (χ2=0.564, P>0.05). There was statistically significant differences in survival between ⅢA and ⅢB or ⅢC stagings (χ2=29.790, 43.060, P 0.05) and between T4aN3a and T4bN2 stagings (χ2=0.029, P>0.05). Conclusions Compared with AJCC TNM staging system 7th edition, N3a and N3b stagings are classified as independent staging in AJCC TNM staging system 8th edition, and 8th edition is more accurate in prognostic evaluation of GC patients in stage Ⅲ. Key words: Gastric neoplasms; American Joint Committee on Cancer; TNM staging; Survival; Prognosis