Central nervous system (CNS) relapse is an undesirable event in the course of patients with diffuse large B cell lymphoma (DLBCL) with a median survival of approximately 6 months following CNS relapse. CNS prophylaxis for the prevention of CNS recurrence, in addition to the standard R-CHOP chemotherapy, is thus preferable. For an overall relapse risk of 2-5%, administration of CNS-directed therapies for all patients with DLBCL is unnecessary and prophylaxis should be targeted for the high-risk patients. CNS-International Prognostic Index (CNS-IPI) score has enabled risk stratification with risk ranging < 1% (low-risk group) compared to > 10% (high-risk group). The latter could be considered for CNS prophylaxis. CNS-IPI, however, is not perfect and may not capture patients with high-risk extra-nodal sites such as testicular DLBCL. Cell-of-origin and MYC/BCL2 expression can further build on CNS-IPI to narrow higher risk patients. CNS prophylaxis strategies are controversial. Common strategies include intrathecal (IT) chemotherapy and systemic CNS penetrants such as methotrexate. IT chemotherapy does not adequately penetrate the brain parenchyma and hence it is insufficient in preventing parenchymal CNS recurrences. Most experts promote systemic methotrexate for high-risk groups, which penetrates both the leptomeningeal and parenchymal CNS compartments. Even though systemic CNS prophylaxis is widely promoted over IT alone, its efficacy is unclear. Ongoing efforts in search for appropriate CNS prophylaxis strategies are warranted. My personal practice is to administer systemic high-dose methotrexate in conjunction with R-CHOP chemotherapy for eligible patients deemed at a high risk of CNS recurrence, especially those with high-risk CNS-IPI and extra-nodal involvement.
Keywords: CNS prophylaxis; Central nervous system (CNS); Diffuse large B cell lymphoma; Intrathecal treatment; Site of CNS relapse; Systemic methotrexate.