Defining Criteria for Diagnosis of Occult Lymphomatous Involvement in Cerebrospinal Fluid

Introduction: Currently, there is no consensus regarding diagnosis and treatment of occult lymphomatous menigeal involvement of cerebrospinal fluid (CSF) in patients with systemic non-Hodgkin lymphomas (NHL), especially in patients with minimal number of clonal cells detected by flow cytometry (FCM) or by cytology.

Aim of the study: To describe a cohort of patients with occult lymphomatous involvement in cerebrospinal fluid including the diagnostic methods as well as management.

Patients and methods: CSF at diagnosis of B-NHL was examined by FCM, cytology, biochemistry and microRNA analysis in a cohort of 62 patients (systemic DLBCL N=45, MCL N=15, Burkitt lymphoma N=2) between 2010 and 2013. Occult meningeal involvement was defined by: a/ FCM: absolute positive number of clonal cells <20 and concomitant negative finding by cytology; b/ FCM negative for clonal cells and concomitant positive finding by cytology; c/ by abundance of increased levels (≥ 200% of the threshold levels) of oncogenic microRNAs (members of miR-17-92 cluster and miR-21, evaulated by Taq-Man RT PCR) in cerebrospinal fluid in patients either passing a/ or b/. The threshold of individual microRNA abundance was defined by statistical analysis of patients with or without CNS involvement. The patients qualified for occult meningeal involvement were considered to be at high risk of CNS relaps. As a control group, the patients with elevated oncogenic microRNAs and negative FCM or cytology of CSF (N=10), were used. All patients received some form of CNS prophylaxis as a part of standard first line treatment.

Results and conclusions: According to described criteria we identified 8 patients with occult meningeal involvement at diagnosis (systemic DLBCL N=4, MCL N=3, Burkitt lymphoma N=1) out of 62 patients: 3 with negative FCM and positive cytology (2-14 cells/ul); and 5 with positive FCM <20 clonal cells and negative cytology, 3 out of them with positive microRNAs. None of these patients with occult meningeal involvement relapsed/progressed into CNS within 12 months. In contrast three out of ten control patients (characterized by elevated oncogenic microRNAs in CSF, but negative for FCM and cytology) relapsed to CNS within 6 months after diagnosis. None of ”triple” negative (FCM, cytology, microRNA) patients (N=44) developed clinically manifest CNS involvement.

These results suggest that examination of oncogenic microRNA in CSF at diagnosis is more sensitive method than FCM and cytology of CSF to detect the patients with occult CNS involvement and higher risk of CNS involvement and this should be reflected in treatment strategy in further clinical trials.

Grants: GACR305 13-12449P, UNCE204021, PRVOUK: P24/LF1/3, P27/LF1/1, P 27/2012 LF3