Outcomes and Relapse Patterns in Primary Central Nervous System Lymphoma: Longitudinal Analysis of 559 Patients Diagnosed from 1983-2020.

BACKGROUND:Contemporary outcomes and relapse patterns in primary CNS lymphoma (PCNSL) are lacking. We analyzed factors associated with relapse in a large cohort with extensive follow up. METHODS:T1-post-contrast-enhancing disease was characterized in immunocompetent PCNSL (diffuse large B-cell) patients from 1983-2020. Patients were stratified by response to induction and consolidation (complete/unconfirmed [CR/CRu], partial, stable, progression [POD]). Refractory was POD during (or relapse ≤3 months of) induction. Initial relapse site was categorized as local (involving/adjacent to baseline), distant intraparenchymal, leptomeningeal, other. Progression-free (PFS) and overall (OS) survival was assessed with proportional hazards. Cumulative incidence with competing risks was used to assess local relapse. RESULTS:Median follow-up was 7.4 years (N=559). Most (321, 57%) were recursive partitioning analysis class 2 (age≥50, KPS≥70). Most had supratentorial (420, 81%), multifocal (274, 53%), bilateral (224, 43%), and deep structure involvement (314, 56%). Nearly all received methotrexate-based induction (532, 95%). There was no difference in PFS or OS from consolidation based on initial response to induction (CR/CRu vs. PR) in patients who ultimately achieved a CR/CRu to consolidation. PFS at 1-, 5-years for 351 patients with CR/CRu to consolidation was 80% (95%CI:76-84%) and 46% (95%CI:41-53%), respectively; 1-year cumulative incidence of local vs non-local relapse was 1.8% vs 15%, respectively. For 97 refractory patients, 1-year cumulative incidence of local vs non-local relapse was 57% vs 42%, respectively. Deep structure involvement (HR 1.89, 95%CI:1.10-3.27) was associated with local relapse in refractory patients. CONCLUSIONS:We report the first comprehensive relapse patterns in a large PCNSL cohort. While relapses post-CR to consolidation are typically distant and unpredictable, refractory patients had a relatively high incidence of local relapse. These findings can help optimize multimodality therapy for this highest-risk population.