Clinical characteristics, treatment, and long-term outcomes in 987 patients with splenic marginal zone lymphoma to inform treatment and surveillance strategies

Splenic Marginal Zone Lymphoma (SMZL) is an indolent non-Hodgkin lymphoma subtype. Due to its rarity, evaluation of real-world data is necessary to inform clinical practice. In this study, adults diagnosed with SMZL between 2000 and 2018 from North America, Europe, and Australia were included and followed until death or last visit. Data were extracted from medical records and regional/national registries. In total, 987 patients with median age of 68 years were included. The 10-year overall survival (OS) estimates were 59% (95%CI: 55-63) from first-line treatment and 49% (95%CI: 43-57) from second-line treatment. First-line splenectomy ( n = 434) and rituximab monotherapy ( n = 121) were associated with an Inverse Probability of Treatment Weighting (IPTW)-adjusted 5-year failure-free survival (FFS) of 52% for splenectomy versus 42% for rituximab; HR 0.70 (95%CI: 0.44-1.13) and adjusted HR for OS of 1.09 (95%CI: 0.59-2.01). The 10-year cumulative risk of transformation from diagnosis was 15% (95%CI: 12-18) with 5-year post-transformation OS of 38% (95%CI: 29-49), and 23% (95%CI: 13-41) for transformation after previous chemotherapy. Lower rates of transformation were seen in patients receiving frontline rituximab. While frontline therapy with either splenectomy or rituximab monotherapy had similarly favorable outcomes, patients had a persistent risk of progression and transformation andsurvival after transformation was poor.