Clinical Relevance of MYD88 L265P Mutation and Interleukin-10 Level in Cerebrospinal Fluid of Patients with Both Newly Diagnosed and Relapsed Primary Diffuse Large B-Cell Lymphoma of the Central Nervous System

Introduction: Early diagnosis remains a major concern in pts with primary diffuse large B-cell lymphoma (DLBCL) of the CNS (PCNSL). Diagnostic delay leads to severe neurological impairment due to prolonged exposure of CNS tissues to tumor infiltration, and protracted steroid therapy, which causes immunodepression and infective complications, the main reasons for treatment interruptions. A few molecular markers have been proposed as diagnostic tools, but reliable parameters that can be easily incorporated in routine practice are still needed. Near 70% of PCNSLs display MYD88 L265P mutation and release high levels of interleukin-10 (IL10). These two parameters are widely used for routine diagnosis of different disorders, but are hardly detectable in peripheral blood of PCNSL pts; accordingly, cerebrospinal fluid (CSF) may be an attractive alternative for their evaluation. Thus, we investigated the sensitivity and specificity of MYD88 L265P mut and IL10 levels in CSF samples to distinguish PCNSL from other neurological disorders, and to identify earlier relapsing lymphomas.

Methods: MYD88 mutational status and IL6 and IL10 levels were assessed by TaqMan RT-PCR assay and ELISA, respectively, on CSF samples from 198 HIV-neg adults with 1) histologically-confirmed PCNSL at presentation (pPCNSL; n= 27) or relapse (rPCNSL; n= 26); 2) neurological disorders currently entering in differential diagnosis with PCNSL (n= 105; degenerative and inflammatory disorders, toxic or infective encephalitis, gliomas, and others); 3) systemic DLBCL at high-risk of CNS dissemination (n= 40). MYD88 status was assessed in 85 neurological controls and interleukins in 78; both parameters were assessed in 58. Differences in MYD88 status (categorical variable) and IL10 levels (continuous variables) among pts subgroups were assessed by Fisher exact and Mann-Whitney U tests, respectively. Predictive accuracy of IL6 & IL10 was evaluated in terms of sensitivity and specificity by means of ROC curves. Associations between PCNSL features (site and number of lesions; CSF protein level and cytological status) and analyzed molecules were addressed by Spearman's correlation.

Results: Demographic characteristics of analyzed subgroups were similar, with a median (range) age of 62 (39-81) ys for PCNSLs and 63 (28-89) ys for controls (p= 0.42); with 27 (51%) and 69 (48%) males (p= 0.70), respectively.

MYD88 L265P mut was detected in 19 (70%) of 27 pPCNSL, in 11 (42%) of 26 rPCNSL, in 1 (1%) of 85 neurological controls and in 1 (3%) of 40 systemic DLBCL (p< 0.00001), with a sensitivity and specificity for pPCNSL detection of 70% and 98%, respectively.

Median IL6 concentration was 4.62 pg/mL (0-157.7) for the 53 PCNSLs and 2 pg/mL (0-200) for the 118 assessed controls (p= 1.0). High IL6 levels (>12 pg/mL) were recorded in 5 (18%) of 27 pPCNSL, in 7 (27%) of 26 rPCNSL, in 7 (9%) of 78 neurological controls, and in 0 (0%) of 40 systemic DLBCL. The ROC curve showed a low sensitivity and specificity of IL6 to distinguish PCNSL from other disorders and DLBCL, with an area under the curve of 0.66 (poor accuracy).

Median IL10 concentration was 53.3 pg/mL (0-400) for PCNSLs and 0 pg/mL (0-10) for controls (p< 0.00001). Increased IL10 levels were recorded in 20 (91%) of 22 assessed pPCNSL, in 20 (91%) of 23 assessed rPCNSL, in 1 (1%) of 78 neurological controls, and in 1 (2%) of 40 systemic DLBCL, with a sensitivity and specificity for PCNSL detection of 91% and 98%, respectively, and an area under the ROC curve of 0.95 (high accuracy).

At least one of analyzed parameters (MYD88 L265P mut & high IL10 level) was recorded in 26 (96%) of 27 pPCNSL, in 23 (88%) of 26 rPCNSL, in 1 (1%) of 58 neurological controls and in 2 (5%) of 40 systemic DLBCL, with a sensitivity and specificity to detect PCNSL of 96% and 97%, respectively. Both MYD88 L265P mut and IL10 levels were independent of lymphoma features.

Conclusions: The occurrence of MYD88 L265P mut and high IL10 level in CSF samples are associated with very high sensitivity and specificity in PCNSL pts. These simple and fast procedures, currently used in routine practice, are reliable tools to generate early and strong suspicion of PCNSL at both diagnosis and relapse. These results support the use of MYD88 L265P mut and high IL10 level as diagnostic tools in pts with suspected PCNSL localized in areas unsuitable for biopsy (i.e., brain stem). The role of these parameters in monitoring lymphoma behavior should be addressed in prospective trials.