Differential prognostic impact of GELTAMO‐IPI in cell of origin subtypes of Diffuse Large B Cell Lymphoma as defined by the Hans algorithm

: The Grupo Espanol de Linfomas y Trasplantes de Medula Osea International Prognostic Index (GELTAMO-IPI) stratifies four risk groups in diffuse large B cell lymphoma (DLBCL) patients treated with immunochaemotherapy: low (LR), low-intermediate (LIR), high-intermediate (HIR), and high (HR). The present study explores the effect of GELTAMO-IPI in the DLBCL subtypes defined by the immunohistochaemistry-based Hans algorithm, Germinal Centre B (GCB) and non-GCB. A multivariate Cox regression model including GELTAMO-IPI risk groups, cell of origin (COO) subtypes and their product was developed to evaluate interaction between the two variables. The COO subtype was available in 839 patients (380 GCB; 459 non-GCB) and both the GELTAMO-IPI and the COO subtype in 780 (353 GCB; 427 non-GCB). There were no differences in 5-year overall survival (OS) between the two subtypes. The Cox model revealed interaction between the GELTAMO-IPI risk groups and the COO subtypes (P = 0·005), indicating that GELTAMO-IPI has a different effect in the two subtypes. Three risk groups were stratified in both COO subtypes: in the GCB subtype, LR, LIR and the combined HIR+HR had 5-year OS of 100%, 75% and 52%, respectively. In the non-GCB subtype, LR, the combined LIR+HIR and HR had a 5-year OS of, 97%, 82% and 35% respectively. GELTAMO-IPI identifies a genuine poor outcome group of patients in the DLBCL non-GCB subtype.