RESUMO
OBJECTIVES: Recent front-line clinical trials used the International Prognostic Index (IPI) to identify trial-eligible patients with newly diagnosed diffuse large B-cell lymphoma (DLBCL). However, many IPI-like variants with improved accuracy have been developed over the years for rituximab-treated patients. METHODS: We assessed the impact of International Prognostic Indices on patient enrolment in clinical trials, aiming to exclude low-risk IPI patients based on POLARIX/EPCORE DLBCL-2 trial criteria. RESULTS: We identified 2877 patients in the Danish Lymphoma Registry who would have been eligible for the POLARIX trial if patients with IPI 0-1 scores were included. IPI and NCCN-IPI assigned 33.3% and 11.9% of patients to the low-risk group, respectively. Shorter 5-year overall survival (91.4% vs. 97.5%), higher relapse rate (9.9% vs. 4.4%), and more deaths (16.1% vs. 4.4%) occurred in the low-risk IPI group compared with low-risk NCCN-IPI group. Analyzed models failed to identify true high-risk patients with poor prognosis. Similar results were found in the confirmatory cohort developed based on EPCORE DLBCL-2 trial eligibility criteria. CONCLUSION: True low-risk patients are more optimal identified by NCCN-IPI and should be excluded from front-line clinical trials due to their excellent prognosis. However, additional high-risk factors besides clinical prognostic models need to be considered when selecting trial-eligible patients.
RESUMO
BACKGROUND: Several clinical prognostic models for diffuse large B-cell lymphoma (DLBCL) have been proposed, including the most commonly used International Prognostic Index (IPI), the National Comprehensive Cancer Network IPI (NCCN-IPI), and models incorporating beta-2 microglobulin (ß2M). However, the role of ß2M in DLBCL patients is not fully understood. METHODS: We identified 6075 patients with newly diagnosed DLBCL treated with immunochemotherapy registered in the Danish Lymphoma Registry. RESULTS: A total of 3232 patients had data available to calculate risk scores from each of the nine considered risk models for DLBCL, including a model developed from our population. Three of four models with ß2M and NCCN-IPI performed better than the International Prognostic Indexes (IPI, age-adjusted IPI, and revised IPI). Five-year overall survival for high- and low-risk patients were 43.6% and 86.4% for IPI and 34.9% and 96.2% for NCCN-IPI. In univariate analysis, higher levels of ß2M were associated with inferior survival, higher tumor burden (advanced clinical stage and bulky disease), previous malignancy and increased age, and creatinine levels. Furthermore, we developed a model (ß2M-NCCN-IPI) by adding ß2M to NCCN-IPI (c-index 0.708) with improved discriminatory ability compared to NCCN-IPI (c-index 0.698, p < 0.05) and 5-year OS of 33.1%, 56.2%, 82.4%, and 96.4% in the high, high-intermediate, low-intermediate and low-risk group, respectively. CONCLUSION: International Prognostic Indices, except for NCCN-IPI, fail to accurately discriminate risk groups in the rituximab era. ß2M, a readily available marker, could improve the discriminatory performance of NCCN-IPI and should be re-evaluated in the development setting of future models for DLBCL.