▪Introduction: Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease and the identification of risk groups is important to plan different therapeutic strategies. The International Prognostic Index (IPI) has been an easy and universal prognostic index during the past 20 years. New prognostic indexes are needed to improve the identification of higher risk groups. The objective of this study is to validate and compare the National Comprehensive Cancer Network International Prognostic Index (NCCN-IPI) and the Grupo Español de Linfomas/Trasplante de Médula ósea (GELTAMO-IPI) in a large cohort of DLBCL patients treated homogeneously with immunochemotherapy in a single institution.Methods: 371 adults with de novo DLBCL consecutive diagnosed from 2004 to 2016 at Insitut Català d'Oncologia in Barcelona and treated with curative intention based on immunochemotherapy [310(81%) R-CHOP, 61 (19%) R-CHOP-like] were included in the analyses. Prognostic indexes were compared in patients with complete data: NCCN-IPI vs. IPI (371 patients) and GELTAMO IPI vs. IPI (268 patients). All survival curves were obtained by the Kaplan-Meier method, and compared using the log-rank test.Results: The number of patients in the low risk (LR), low-intermediate risk (LIR), High-intermediate risk (HIR) and high risk (HR) groups are shown in table 1. OS curves for each prognostic index are shown in Figure 1. In all the risk indexes, the four risk groups had 5-yearOS and PFS rates with significant differences in the global comparisons. The NCCN-IPI discriminated better low-risk subgroups than IPI (5-year OS: 90.6% vs 75.5%, respectively). The GELTAMO-IPI compared to IPI improved the discrimination of the LR group (5-year OS: 81.8% vs 75.5%, respectively) and the HR group (5-year OS: 26.4% vs 39.4%, respectively).Conclusion: GELTAMO-IPI has been validated in an independent cohort of patients equally treated in a single centre. GELTAMO-IPI is a good prognosis index capable of differentiating a high-risk group with a 5-year OS of 26% unlike NCCN-IPI and IPI. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.