Clinical, Biological, and Treatment-Related Predictors of Central Nervous System Relapse in Diffuse Large B-Cell...

Background/Objectives: Central Nervous System (CNS) relapse represents a severe and often fatal complication of Diffuse Large B-Cell Lymphoma (DLBCL). This study aimed to evaluate clinical, biological, and treatment-related factors associated with progression-free survival (PFS) until CNS relapse in patients with DLBCL. Methods: A retrospective cohort study was conducted using clinical data from adult DLBCL patients evaluated and treated at the Regional Institute of Oncology, Iași, Romania, between 2015 and 2023. Associations between clinical, biological, and treatment-related variables and CNS relapse were evaluated using univariate and multivariable Cox proportional hazards models, Fine-Gray competing-risk analyses, and propensity score-based methods to address confounding by indication for CNS prophylaxis. Results: Twenty-six CNS relapse events (6.3%) and 72 deaths without prior CNS relapse occurred over a median follow-up of 12 months. In the prespecified reduced multivariable Cox model, non-R-CHOP regimens (HR 4.57, 95% CI 1.67-12.52; p = 0.003) and high CNS-IPI scores (HR 4.70, 95% CI 1.14-19.46; p = 0.033) were independently associated with CNS relapse. The 20-month cumulative incidence of CNS relapse was 7.0% in the R-CHOP-like group versus 35.2% in the non-R-CHOP group (Gray's test p < 0.001). Fine-Gray modeling confirmed the association for non-R-CHOP regimens (SHR 3.38, 95% CI 1.21-9.45; p = 0.02). Cell-of-origin subtype, double-expressor phenotype, and Ki-67 were not significantly associated with CNS relapse. Conclusions: High CNS-IPI and treatment with non-R-CHOP regimens independently predicted earlier CNS relapse. Future multicenter studies with molecular profiling are needed to refine CNS risk stratification.