The risk of venous thromboembolism in primary central nervous system lymphoma: a systematic review and meta-analysis

Primary central nervous system lymphoma (PCNSL) is a rare extranodal lymphoma localized to the central nervous system. Small single-center studies have suggested that patients with PCNSL may be at high risk of venous thromboembolism (VTE). This systematic review aimed to estimate the risk of VTE in patients with PCNSL. A systematic review was conducted using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. MEDLINE, Embase, and CINAHL were searched from 1990 to 2022. Prospective and retrospective observational studies as well as clinical trials were included. The primary efficacy outcome was VTE, and the primary safety outcome was major bleeding as defined by the individual studies. After screening 883 studies, 46 studies (3688 patients) with PCNSL were included. Mean age was 62.4 years. Five studies explored the use of thromboprophylaxis (acetyl salicylic acid or anticoagulation [n = 1]) and low-molecular-weight heparin (n = 4). Overall, 420 patients developed VTE (11.4%), including 17 fatal events (4% of all VTE). Two studies that reported on VTE prophylaxis representing 77 patients identified 8 breakthrough VTE events (10.4%). Most studies (n = 34; 74.5%) did not report major bleeding complications. Among studies reporting on bleeding, 174 major bleeding (7.4%) events were reported out of 2361 patients, 3 of which were attributed to thromboprophylaxis. Patients with PCNSL seem to be at high risk of both VTE and bleeding complications. Future clinical trials in this population should routinely collect data on incidence of VTE and bleeding to help clinicians assess the risk-to-benefit ratio of thromboprophylaxis in this high-risk patient population.