A clinically based prognostic index for diffuse large B-cell lymphoma with a cut-off at 70 years of age significantly improves prognostic stratification: Population-based analysis from the Danish Lymphoma Registry

The introduction of rituximab and generally improved health among elderly patients have increased the survival of patients with diffuse large B-cell lymphoma (DLBCL). The International Prognostic Index (IPI) from 1992 is based on pre-rituximab data from clinical trials including several lymphoma subtypes. We applied IPI factors to a population-based rituximab-treated cohort of 1990 patients diagnosed 2000-2010 and explored new factors and the optimal prognostic age cut-off for DLBCL. Multivariate-analyses (MVA) confirmed the prognostic value of all IPI factors except the presence of > 1 extranodal lesion. The optimal age cut-off was 70 years. In a MVA of albumin, lymphocyte count, sex, immunoglobulin G, bulky disease, hemoglobin and B-symptoms, only albumin was prognostic. We propose: (1) a modified DLBCL prognostic index (DLBCL-PI) including: age (70 years), performance status (PS), lactate dehydrogenase (LDH), stage and albumin level, and (2) a separate age-adjusted DLBCL-PI for patients <70 years including PS, LDH, albumin level and > 1 extranodal lesion, however excluding stage.