Effect of addition of rituximab to CHOP on survival of patients in both the GCB and non-GCB subgroups of diffuse large B-cell lymphoma

Abstract

8040 Background: Diffuse large B-cell lymphoma (DLBCL) includes at least two prognostically important subgroups, i.e. germinal center B-cell (GCB) and activated B-cell (ABC) DLBCL, which were initially characterized by gene expression profiling and subsequently validated by immunostaining. Bcl-2 has also been identified as a prognostic indicator in the ABC subgroup. However, with the addition of rituximab (R) to standard chemotherapy, the prognostic significance of this subclassification of DLBCL is unclear. Methods: We studied 119 cases of de novo DLBCL including 70 cases treated with R-CHOP and 49 cases treated with CHOP. The cases were assigned to either the GCB or non-GCB subgroups using the methodology described by Hans et al (Blood 2004; 103:275). Characteristics of the patients were compared using the Chi-square test. Overall survival (OS) and event-free survival (EFS) were estimated using the Kaplan Meier method and compared with the log-rank test. Results: The median age of the 119 patients was 67 years, ranging from 20 to 90 years, and there were 62 males and 57 females. The clinical characteristics of patients treated with CHOP versus R-CHOP, including the IPI, were comparable. R-CHOP was more effective than CHOP with improved 5-year EFS (63% vs 41%, p=0.013) and OS (78% vs 47%, p<0.001). In both patient groups treated with R-CHOP or CHOP, the GCB subgroup had a significantly better 5-year EFS and OS compared to the non-GCB subgroup (OS: 91% vs 64% for R-CHOP, p=0.0073; 67% vs 31% for CHOP, p=0.034, respectively). Additionally, both the GCB and non-GCB subgroups treated with R-CHOP had a significantly improved OS compared to their respective subgroups receiving CHOP alone (GCB, p=0.015; non-GCB, p=0.019). Bcl-2 expression was not a significant predictor in either the GCB or non-GCB subgroups treated with R-CHOP (OS, GCB: p=0.32; non-GCB: p=0.43). Conclusions: In this retrospective study, we demonstrate that subclassification based on the cell of origin continues to have prognostic significance in patients with DLBCL treated with R-CHOP. Addition of rituximab to CHOP improves the overall survival of patients with DLBCL in both the GCB and non-GCB subgroups. No significant financial relationships to disclose.