The Revised International Prognostic Index (R-IPI) for Diffuse Large B-Cell Lymphoma was developed by Sehn and colleagues at the British Columbia Cancer Agency in 2007, in response to the observation that the original IPI (developed in the pre-rituximab era) lost its ability to distinguish four separate risk groups when applied to patients treated with R-CHOP. In the R-CHOP era, original IPI "low-intermediate" and "high-intermediate" risk groups merged into a single outcome group. The R-IPI collapses the five original IPI categories into three clinically meaningful groups (Very Good, Good, Poor) with substantially different 4-year OS and PFS estimates, providing better guidance for treatment intensification decisions.