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

Summary The Grupo Español de Linfomas y Trasplantes de Médula Ósea 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.