Prognostic Value of the Novel Mucosal Associated Lymphoid Tissue Prognostic Index (MALT-IPI) in Marginal Zone Lymphoma (MZL) Cases

Background/Objective: Marginal zone B-cell lymphomas (MZL) represent a heterogeneous group of indolent lymphomas, comprising of MALT lymphomas, nodal MZL and splenic MZL. Currently, there has been no widely accepted prognostic indices for these lymphomas. Recently, the International Extranodal Lymphoma Study Group (IELSG) developed a novel simplified MALT prognostic index (MALT-IPI)1, which was subsequently validated by a western cohort of MALT cases. To date, there has not been an assessment of the applicability of this score in other subtypes of MZL or in the Asian population, where geographic and ethnical differences may influence disease epidemiology and outcomes. Our study aimed to 1) Evaluate clinical characteristics and survival outcomes for a large cohort of Southeast Asian patients with MZL who were diagnosed between 1993 - 2018 and ii) Assess the prognostic significance of the MALT-IPI for this patient cohort. Patients and Methods: We retrospectively studied 286 consecutive patients with newly diagnosed MZL treated between 1993 to 2016 at 2 tertiary cancer centres in Singapore. Data on clinical parameters, treatments, response, and survival were evaluated. In addition, all patients with available data were classified according to the MALT-IPI (N =236, including MALT lymphomas N= 190 and nodal/splenic MZL, N= 46) and the prognostic significance of this score was evaluated. Results: Among 286 patients with MZL, 230 patients (80%) had MALT lymphomas, 35 (12%) had nodal MZL and 21 (7%) had splenic MZL. The median age was 60 years (range 15- 94), 49% of the patients were male and 183 patients (64%) had Stage I-II disease. The majority of the patients were managed by either radiotherapy (N= 77, 27%), chemo and/or immunotherapy (N= 76, 27%), watchful waiting (N-= 46, 16%) or antibiotics (N= 33, 11.5%).With a median follow-up of 46 mths (range 1 - 266 mths) for all patients, the 5 yr-PFS for the cohort was 59.8 %. Progression free survival was significantly better for the MALT subgroups compared to the nodal and splenic MZL subgroups ( 5 yr PFS of 63.6 vs 49.7 % vs 30.5 % respectively, p=0.002). The 5-yr OS was excellent at 86.7% and there were no differences between the MALT, nodal MZL and splenic MZL cohorts (5-yr PFS 87.1 vs 85.3% vs 86.4, p=0.667). Age, ECOG status and elevated LDH were prognostic for PFS on univariate analysis but none has significant impact on multivariate analysis. No other baseline clinical characteristic (including gender and di