Secondary CNS relapse in diffuse large B-cell lymphoma: defining high-risk patients and optimization of prophylaxis strategies.

Despite improvement in survival in diffuse large B-cell lymphoma (DLBCL) with the introduction of rituximab, central nervous system (CNS) relapse continues to represent a clinical challenge. A number of studies have evaluated clinical risk factors in an attempt to identify high-risk patients to direct CNS staging investigations and consider prophylaxis strategies. The CNS International Prognostic Index is a robust and reproducible risk model that can identity patients at high risk of CNS relapse, but its specificity remains limited. Studies are emerging of biomarkers that predict CNS relapse that can be integrated with clinical risk models to better identify high-risk patients for CNS-directed prophylaxis strategies. Because CNS parenchymal disease is the predominant compartment, prophylaxis should include deeply penetrant drugs such as high-dose methotrexate. However, this has been associated with toxicity and has limited use in older patients. Novel therapies are being tested in primary CNS lymphoma with encouraging results and may represent rational strategies to be further explored in the prophylaxis setting.