Central nervous system involvement in diffuse large B-cell lymphoma: an analysis of risks and prevention strategies in the post-rituximab era.

Central nervous system (CNS) relapse in patients with diffuse large B-cell lymphoma (DLBCL) occurs infrequently (approximately 5%), but is almost universally fatal. Controversy exists regarding which factors most reliably identify high risk patients in the post-rituximab era. Clarification is also needed regarding the value of prophylaxis strategies when contemporary rituximab-based chemotherapy regimens (chemoimmunotherapy) are used. A systematic review with focus on the era of chemoimmunotherapy has been performed. Involvement of > 1 extranodal site plus an elevated lactate dehydrogenase level identifies individuals at highest risk (> 20%) for CNS recurrence who merit additional evaluation. Only certain solitary extranodal sites (testis, kidney and breast, but not bones, orbit or epidural space) appear to confer higher risk in patients receiving chemoimmunotherapy. Data from studies employing modern regimens suggest that intrathecal prophylaxis is ineffective even for high risk populations. Systemic prophylaxis (e.g. high dose methotrexate) may be useful, but does not have strong support in the literature. A significant portion of patients with high risk features (˜25%) may already have subclinical CNS disease, which requires alternative detection and treatment strategies. Flow cytometry is a promising approach with increased sensitivity. Widespread use of this approach could redefine what risk and prophylaxis mean. An algorithm for incorporating risk factors, evaluation and treatment is presented.