Refined prognostic staging for resected pancreatic cancer by modified stage grouping and addition of tumour grade

Background With changes in T and N categories the 8th edition of the AJCC/UICC TNM staging system for pancreatic cancer resulted in improved prognostic staging, but inconsistencies were observed with specific stage groups. Tumour grading remains disregarded in prognostic staging. We aimed to validate the current staging system and to investigate the possibility of further optimization by integration of grading. Methods 1946 patients undergoing upfront surgical resection for pancreatic adenocarcinoma from 10/2001 to 12/2015 were identified from a prospective institutional database. Survival analyses based on the 8th UICC TNM edition were performed and rare TNM subgroups were reallocated based on survival. The impact of tumour grade on stage-specific survival was assessed and a TNMG staging system was developed. Results The 8th UICC staging system accurately stratified prognosis except for comparable survival in stages IB (pT2N0M0) and IIA (pT3N0M0). Regrouping of pT3N0M0 and pT1N1M0 to IB and of pT1N2M0 to II resulted in a modified staging system with higher consistency. High tumour grade (G3&G4 vs G1&G2) was associated with a significantly shorter survival in all new stage groups except for stage IV modified UICC. A TNMG-based prognostic stage grouping in which high tumour grade results in grouping with tumours of the next higher pTNM-stage resulted in improvement of prognostication in non-metastatic pancreatic cancer. Conclusions The 8th edition of the UICC TNM staging system leaves room for improvement. A TNMG staging system with adjustments in group-allocation of specific rarely occurring pTNM subgroups and integration of tumour grade results in improved prognostic stratification.