The highest prognostic impact of LDH among International Prognostic Indices (IPIs): an explorative study of five IPI factors among patients with DLBCL in the era of rituximab

Although the International Prognostic Index (IPI) is considered as the current standard prognostication system for diffuse large B-cell lymphoma (DLBCL), prognostic heterogeneity is suggested to exist among the patients within the same IPI risk group. Hence, we investigated the pattern of distribution and prognostic impact of five IPI factors within the same IPI score. We retrospectively reviewed the medical records of 387 patients newly diagnosed as pathologically proven DLBCL between February 2002 and February 2010. We classified patients to IPI risk scores and categorized them according to the combinations of IPI. Then, we explored the frequency of five IPI factors and analyzed the correlation between these subgroups and efficacy outcomes: complete response (CR), event-free survival (EFS), and overall survival (OS). Survival estimates by IPI score in this cohort corresponded to the classic IPI. Elevated serum level of lactate dehydrogenase (LDH) was the most prevalently distributed factor throughout the scores, and patients with elevated serum level of LDH tended to have lower CR, inferior EFS, and/or OS irrespective of IPI scores. Particularly, among the subgroups of IPI score of 2, elevated serum level of LDH was significantly associated with inferior CR (73.1 vs 95.2 %), 3-year EFS (57 vs 87 %), and 3-year OS (58 vs 82 %). In addition, the higher serum level of LDH, particularly above 2,000 IU/L, was significantly correlated with the inferior survival outcomes (3-year EFS 78.0 vs 58.5 vs 45.5 vs 20.0 %, 3-year OS 86.0 vs 66.2 vs 58.2 vs 40.0 %). In conclusion, among five factors of IPI, elevated serum level of LDH seems to be the most frequently distributed and, more importantly, the most relevant IPI factor with the highest prognostic impact. These findings still warrant further validation in larger cohorts.