Secondary CNS lymphoma: the poisoned needle in the haystack

The term secondary central nervous system (CNS) lymphoma (SCNSL) defines the involvement of the CNS at presentation or relapse in patients with systemic lymphoma. In the 1990s, most reported studies on SCNSL were focused on pediatric series and/or highly aggressive lymphomas. Subsequently, some retrospective studies of adult patients with 'high-grade' lymphomas aimed to identify factors predicting CNS dissemination and several series of rare extranodal lymphomas with varied risk of CNS involvement were reported. More recently, studies on the effect of rituximab on CNS recurrence rate, some proposals of risk scores and the first prospective trials focused on CNS prophylaxis or treatment of SCNSL were published. Despite all these efforts, the level of evidence remains low, and some criticisms of reported studies keep many questions open. In this issue of Annals of Oncology, Gleeson et al. [1] on behalf of the UK NCRI, add new knowledge to this challenging field. The authors analyzed CNS events in 1080 patients with diffuse large B-cell lymphomas (DLBCL) registered in the NCRI R-CHOP14vs21 trial, and, as the main findings, they report a CNS recurrence rate of 1.9% for the whole series and 2.8% for patients selected to receive CNS prophylaxis [1]. Unfortunately, the authors did not identify risk factors, probably due to the small number of events, but they documented CNS relapse sites and confirmed that prognosis of SCNSL patients is poor. The authors should be commended for the collection of a huge mass of data and for the good-sense analysis performed.

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