O151 A comparison of pathological TNM 7 with TNM 8 staging for pancreatic ductal adenocarcinoma and distal cholangiocarcinoma

Abstract

Abstract Background The 8th edition of the TNM (tumour, nodes and metastasis) staging system was introduced in 2016 to improve the prognostic prediction of pancreatic ductal adenocarcinoma (PDAC). However, its superiority over the previous edition remains uncertain. This study evaluated the prognostic impact of TNM 7 with TNM 8 staging in patients with PDAC and distal cholangiocarcinoma. Methods A retrospective cohort study was conducted using electronic healthcare databases at a tertiary hepatobiliary centre in the UK. Kaplan-Meier survival curves were used to evaluate the prognostic prediction of TNM 7 and TNM 8 staging. The concordance index was calculated to assess the discriminatory power of both systems. Crosstabulation of T, N and overall staging was performed to determine which staging system stratified patients more effectively. Results The study identified 194 patients and found the overall median survival after resection to be 1.86 years. The concordance index for TNM 7 [0.634; 95% confidence intervall(CI) 0.586-0.682)], was similar to TNM 8 (0.633; 95% CI 0.584-0.683). TNM 8 showed improved stratification of patients for the T (p=0.001), N (p=0.001) classifications and overall staging system (p=0.001). However, in TNM 8, the new N2 stage had a similar survival prediction to N1. Conclusion There was no significant difference in the prognostic prediction between the TNM 7 and TNM 8 systems for PDAC and distal cholangiocarcinoma. While TNM 8 improved patient stratification across T staging, our findings found the introduction of the N2 staging to be unnecessary as its survival prediction was comparable to N1.