Comparison of the 2010 AJCC TNM staging system with a modified lymph node ratio staging system in 7,233 gastric cancer patients.

Abstract

4023 Background: The 2010 AJCC staging system for gastric cancer modifies T and N definitions, but continues to base N stage on the absolute number of positive nodes (PN) regardless of the number of examined nodes (EN). With decreases in EN, the lymph node ratio (NR, ratio of PN to EN) may better stage patients. Methods: 7,233 gastric cancer patients who underwent gastrectomy between 1998 and 2006 were identified from the SEER database. Patients were classified into 5 NR groups according to a modified NR algorithm. TNRM staging system was constructed using the log-rank test. Overall survivals based on 2010 AJCC and TNRM staging systems were compared. Results: The median number of EN was 10 and 69% of patients had <16 EN. Both 2010 AJCC and TNRM staging systems were statistically significant prognostic factors (p<0.001). 5-year survivals (5YS) based on these systems are shown in the Table. When stratified by TNRM stage, 6 out of the 9 TNM stages (IA, IIA-B, IIIA-C) represented patients with statistically heterogeneous prognosis with the largest range of 5YS being 36% (stage IIB). In contrast, when stratified by AJCC stage, 3 of 8 TNRM stages (3, 7, 8) represented patients with statistically heterogeneous prognosis with the largest range being only 18% (stage 3). Using ±5% of estimated 5YS as a threshold for misclassification, 49% of patients were inaccurately staged by the AJCC system while this rate dropped to 7% with the TNRM system. Conclusions: The 2010 AJCC staging system does not optimally stratify survival in SEER gastric cancer patients given the majority of patients have <16 EN. A modified TNRM system is a more accurate means of staging these patients. TNRM 1 2 3 4 5 6 7 8 p value* AJCC TNM 5 YrS (#PTs) 81%(217) 67%(1,211) 52%(213) 40%(715) 28%(1212) 17%(1344) 6%(777) 2%(1,544) <0.001 0 76% (186) 82% 74% 0.12 IA 71% (647) 81% 68% <0.001 IB 60% (454) 66% 42% 50% 0.07 IIA 46% (915) 68% 60% 35% 36% <0.001 IIB 31% (892) 53% 46% 29% 17% <0.001 IIIA 19% (882) 28% 15% 8% <0.001 IIIB 14% (1387) 24% 18% 5% 5% <0.001 IIIC 8.0% (934) 29% 20% 10% 4% <0.001 IV 2.0% (936) 2% - p value* <0.001 0.97 0.25 <0.001 0.14 0.07 0.46 0.03 <0.001 * p value of testing the heterogeneity within each TNM or TNR M stage. No significant financial relationships to disclose.