Clinical Outcomes of Treatment-Naive Transformed vs. De Novo Diffuse Large B-Cell Lymphoma: A Propensity...

Background: The prognostic significance of histological transformation (HT) in treatment-naive diffuse large B-cell lymphoma (DLBCL) remains controversial. This study aimed to evaluate the clinical outcomes and failure patterns of treatment-naive transformed DLBCL (trDLBCL) compared with de novo DLBCL using a large-scale cohort. Methods: We retrospectively analyzed 1735 consecutively enrolled treatment-naive DLBCL patients (118 trDLBCL and 1617 de novo). Propensity score matching (PSM) was performed to balance baseline characteristics. Survival outcomes were assessed using Kaplan-Meier and Cox proportional hazards models. Subgroups were defined by pathology (t-FL vs. t-MZL) and pattern: concurrent (synchronous indolent lymphoma and DLBCL components at diagnosis) vs. pure transformation (DLBCL occurring as the sole histology in patients with a prior history of untreated indolent lymphoma). Results: In the overall cohort, trDLBCL was associated with significantly inferior progression-free survival (PFS) compared with de novo disease and remained an independent adverse prognostic factor in multivariable analysis (HR 1.754, p < 0.001). These findings were confirmed in a 1:1 propensity score-matched cohort (108 pairs), where trDLBCL continued to show worse PFS (p < 0.01), while overall survival (OS) was comparable (p = 0.99). Within trDLBCL patients, the underlying indolent subtype (t-FL vs. t-MZL) did not significantly affect survival (PFS p = 0.17, OS p = 0.35), whereas "pure transformation" was associated with markedly inferior PFS (p = 0.005) and OS (HR 2.56, p = 0.02) compared with concurrent transformation. Failure pattern analysis revealed a higher risk of early progression in trDLBCL (POD24: 30.56% vs. 18.52%; OR 1.94, 95% CI: 1.05-3.56), whereas central nervous system (CNS) involvement was low and comparable between groups (2.78% vs. 0.93%, p = 0.62). Conclusions: Treatment-naive trDLBCL is associated with inferior PFS driven by early progression, whereas OS is comparable due to effective salvage therapies. Pure transformation appeared to define a higher-risk subgroup with inferior disease control, supporting the need for future prospective studies to evaluate risk-adapted frontline, consolidation, or maintenance strategies.