A Prognostic Index for Extranodal Marginal-zone Lymphoma Based on the Mucosa-associated Lymphoid Tissue International Prognostic Index and Serum β2-microglobulin Levels

The mucosa-associated lymphoid tissue (MALT) International Prognostic Index (IPI) was recently proposed as a prognostic index for patients with MALT lymphoma. We aimed to investigate the prognostic value of the serum β2-microglobulin level in the context of MALT-IPI, and we proposed a new prognostic index. Survival outcomes were analysed with regard to β2-microglobulin level, MALT-IPI, and the new prognostic index in MALT lymphoma patients (n = 571). The validity of the new prognostic index was assessed using an independent cohort (n = 216). Patients with high β2-microglobulin levels had significantly worse progression-free survival (PFS) and overall survival (OS) outcomes. A high β2-microglobulin level was independently associated with poor PFS and OS. β2-microglobulin levels further stratified patients in the MALT-IPI intermediate-risk group in terms of PFS and OS. A new prognostic index based on the MALT-IPI and the β2-microglobulin level, MALT-IPI-B, was proposed. The MALT-IPI-B was able to stratify patients into subgroups having distinct PFS and OS outcomes in both the training and validation cohorts. MALT-IPI-B enabled the identification of patients with poor survival outcomes who were classified into the intermediate-risk group by the MALT-IPI. In conclusion, this new β2-microglobulin-based prognostic index may have the specific advantage of identifying high-risk patients who may require systemic treatment.