[18F]Fluoromethylcholine PET/CT for CNS lymphoma assessment: a new tool

Background Central nervous system (CNS) lymphomas are a rare subset of lymphoma, which are associated with a poor outcome. The gold standard for CNS imaging is with gadolinium-enhanced magnetic resonance imaging (MRI); however, there are a number of limitations, including some patients with small persistent abnormalities from scarring due to focal haemorrhage or from a previous biopsy, which can be difficult to discern from residual tumour. [18F]Fluoromethylcholine positron emission tomography–computed tomography (FCH-PET/CT) uses an analogue of choline, which due to the upregulation of choline kinase in tumour cells, allows increased uptake of FCH. As there is minimal background grey matter uptake of FCH, FCH-PET/CT can be used in CNS imaging and provide a useful tool for response assessment. Methods This is a cohort study, where we identified 40 patients with a diagnosis of primary or secondary CNS lymphoma between 1st November 2011 and 10th October 2019. Results 26 of the 40 patients (65%) had concordant results. Of the discordant results, 11 out of 14 had partial response (PR) on MRI but showed a metabolic complete response (mCR) on FCH-PET. The overall response rates (ORR) were similar between the two modalities (90% for MRI versus 95% with FCT-PET/CT). Conclusion We conclude that FCH-PET/CT is a reasonable alternative mode of imaging to gadolinium-enhanced MRI brain imaging, providing a new tool for assessment of CNS lymphoma.

Regulation of CNS Lymphoma Progression By the Myeloid Microenvironment

;'Insights into the molecular and immunologic pathogenesis of primary CNS lymphomas are essential for meaningful progress in therapy. Tumor-associated macrophages represent the dominant infiltrating leukocyte and there are few established insights into their phenotypes and role in this disease. While upregulation of Th2 cytokines IL-4 and IL-10 in the microenvironment has been demonstrated, the relative roles of M1 and M2 macrophages in contributing to CNS lymphoma pathogenesis has not been elucidated. To date, there is also no information regarding the relative contributions of brain resident microglia and infiltrating macrophages and their interactions with lymphoma. Additional key questions include the identification of factors that mediate both immune cell chemotaxis in CNS lymphomas, as well as the relationship between myeloid cell infiltration and T-cell mediated immune surveillance and immunosuppression. We combined analyses of clinical specimens and mechanistic studies using preclinical in vivo models and show evidence that infiltrating tumor-associated macrophages, derived from monocyte precursors, have a critical role in attenuating CNS lymphoma progression. Immunohistochemical analysis of the density and morphologic features of CD68+ tumor-associated macrophages in 62 diagnostic specimens of immunocompetent PCNSL demonstrated that smaller macrophage size and lower macrophage density correlated with significantly shorter OS. Evaluation of CD68 immunoreactivity using image analysis software (ImageJ) confirmed the heterogeneity of macrophage size and infiltrative density in PCNSL. A multivariate Cox model including age, IELSG score, receipt of consolidation and/or maintenance therapy demonstrated that tumor-associated macrophage density (both count and area) was a significant, independent predictor of favorable PFS and OS and that larger macrophage size a significant, independent predictor of OS in PCNSL treated with standard MTX-based induction (predominantly MTX, temozolomide, rituximab). Using a variety of syngeneic and non-syngeneic preclinical models, including patient-derived CNS lymphoma cells, as well as diagnostic clinical specimens, we characterized the phenotype of tumor-associated macrophages in PCNSL. Using flow-cytometry, we demonstrated that while CD45 high tumor-associated macrophages exhibit strong expression of the canonical M2 marker CD206, a scavenger receptor, these also displayed high co-expression of iNOS and MHC II, markers of classically-activated M1 macrophages. Pharmacologic inhibition of the CSF-1 receptor led to accelerated CNS lymphoma progression, attenuated T-cell infiltration and blocked rituximab efficacy. A flow-cytometric assay of phagocytosis, using Raji lymphoma transduced to express mCherry, demonstrated that infiltrating CD206+ macrophages are the dominant mediator of lymphoma phagocytosis. We applied 2P intravital imaging of a CNS lymphoma model using Cx3cr1GFP/+:Ccr2RFP/+ myeloid cell dual reporter mice and transcriptional studies to define the time-dependent infiltration and phenotypic changes in tumor-associated macrophages and microglia that correlate with disease progression. Using IFN-γ -/- mice we identified a critical role for IFN-γ in the regulation of CNS lymphoma, in the presence and absence of T-cells. We identified IFN-γ-regulated genes in tumor-associated macrophages that may contribute to direct lymphoma cytotoxicity as well as stimulation of T-cell chemotaxis and antigen processing, including TAP1 and TAP2. By IHC, we confirmed TAP1 expression in a subset of diagnostic specimens of PCNSL and determined, using Cox multivariate model, that strong TAP1 correlated with improved PFS (p<0.0006). Notably, independent of receipt of maintenance therapy, TAP1 also correlated with improved PFS in 38 patients that received only MTX-based induction, without dose-intensive chemotherapy consolidation. (Figure 1) Our results support a direct, immune-editing role for monocyte-derived macrophages in the regulation of CNS lymphoma progression, via several mechanisms, including antigenic processing and cross-presentation. We suggest that tumor-associated CD68 and TAP1 (and TAP2) be evaluated further as candidate biomarkers for risk stratification in PCNSL, particularly in trials that involve targeted immunotherapy. Supported by NCI and LLS. Figure 1 Figure 1. Disclosures Rubenstein: Kymera: Research Funding.

Preliminary Results of Zanubrutinib-Containing Regimens in DLBCL and Cerebrospinal Fluid Distribution of Zanubrutinib

Background: Zanubrutinib is a second-generation Bruton's tyrosine kinase (BTK) inhibitor. The safety and efficacy of zanubrutinib in CNS lymphoma are unknown, as well as its brain distribution through the blood-brain barrier. Objective: A retrospective study of zanubrutinib-containing regimens was performed in patients with DLBCL to evaluate the efficacy of zanubrutinib. Paired plasma and cerebrospinal fluid (CSF) samples were collected to assess zanubrutinib's permeability through the BBB. Methods: Consecutive DLBCL patients treated with zanubrutinib-containing regimens from August to December 2020 in PUMCH were recruited. Paired plasma and CSF samples were collected at a fixed time point after zanubrutinib administration. Plasma and brain zanubrutinib quantification was performed by liquid chromatography-tandem mass spectrometry. Results: Totally 13 patients were enrolled, including primary CNS lymphoma (n=8) and systemic DLBCL (n=5). 53.8% (7/13) were refractory/relapsed, 84.6% (11/13) had CNS involvement. Overall response rates (ORRs) were 84.5% and 81.8% in the whole population and CNS involved cases, respectively. A total of 23 time-matched plasma-CSF sample pairs were collected. The mean peak concentration of zanubrutinib in the CSF was 2941.1 pg/ml (range, 466-9032.0). The corrected mean CSF/plasma ratio by protein binding of 94.0% was 42.7±27.7% (range, 8.6-106.3%), indicating the good penetrating ability through the BBB of free drug. The CSF/plasm ratio was not influenced by sex, DLBCL subtype, co-administrated BBB penetrating drugs or plasma drug concentration. Conclusion: This preliminary study revealed the efficacy of zanubrutinib-containing regimens in DLBLC, especially CNSL, for the first time. The excellent BBB penetration of zanubrutinib supports its further investigation in CNS lymphomas. Disclosures Li: Astellas Pharma, Inc.: Research Funding. OffLabel Disclosure: Zanubrutinib is a selective Bruton Tyrosine kinase(BTK) inhibitor and is approved for WM, MCL and CLL/SLL in the Unite States and China. BTK inhibitors such as ibrutinib and tirabrutinib are highly effective in CNS lymphoma and have good penetration ability of brain-blood-barrier. We supposed that zanubrutinib should be effective in DLBCL and CNS lymphomas just as other BTKi,so we prescribed zanubrutinib in this study.

Prognostic significance of immunohistochemical markers in Primary CNS lymphomas

Primary CNS lymphoma (PCNSL) is a rare form of extra nodal Non-Hodgkin Lymphoma that is typically confined to the brain, spinal cord, lepto meninges and eyes. We studied the clinico pathological features of PCNSLs, immuno histochemical (IHC) markers expressed and the association of morphological features & IHC markers with clinical outcome. 30 cases of primary CNS lymphomas were studied. 25 cases were diffuse large B cell lymphomas, which were sub classified using Hans algorithm into GCB and non-GCB. The IHC markers done were CD20, CD3, BCL2, BCL6, MUM-1, CD10 and c-myc. Mean proliferation index Ki was 80%. Follow up and survival data was collected and the association of each IHC marker and subtype with prognosis was assessed. PCNSL forms around 2% of all lymphomas as well as primary CNS tumours. Non GCB type is more common (72%). Mean overall survival was 9.7 months. Ki-67 index of 80% or more is the only independent variable of prognostic significance. None of the other IHC markers or sub typing had any influence on the outcome.

P14.88 Management of primary CNS lymphomas. Experience of 32 cases

BACKGROUND Lymphomas (primary and secondary) are rare tumors of the central nervous system. They can involve both the supratentorial areas and the posterior cranial fossa. Modern management of patients with suspected CNS lymphoma should include a stereotactic or navigation-guided biopsy and subsequently carrying out chemotherapy and, in rare cases, radiosurgery. MATERIAL AND METHODS We analyzed our experience of the diagnosis and treatment of PCNSL. Our work included 32 patients with PCNSL. The study did not include patients with suspected CNS lymphoma, according to MRI data, in whom the diagnosis was not confirmed after biopsy. RESULTS Thirty patients underwent biopsy (20 - navigation guided, 1 - open, 9 - “burr hole”) with preliminary intraoperative histological verification. Gross total resection was performed in 2 cases since, according to preoperative MRI data, it was assumed that the patient had glial tumors. Postoperative histological examination confirmed the diagnosis of CNS lymphoma in all cases. Subsequently, after detailed histological and immunohistochemical studies, 30 patients underwent intra-arterial chemotherapy or high-dose chemotherapy according to NCCN protocols. Palliative treatment was recommended in 2 cases due to acute deterioration of patients. In our work, we would like to present a diagnostic algorithm and treatment regimens used in the management of our patients. CONCLUSION In the treatment of CNS lymphomas, careful histological verification is required, which is possible if several key points are performed - discontinuation of dexamethasone at least 24 hours before the biopsy, MRI for intraoperative neuronavigation after discontinuation of dexamethasone, intraoperative preliminary histological verification. In our opinion, complete removal of the tumor is possible if there are no risks of developing a persistent neurological deficit. Various methods of opening the blood-brain barrier are currently used, which can significantly reduce the effective dosage of drugs and, accordingly, the side effects. Further research is needed to determine the dependence of the prognosis of the disease on the type of surgery (biopsy or resection).

Epstein-Barr Virus Induced Cytidine Metabolism Roles in Transformed B-Cell Growth and Survival

Epstein-Barr virus (EBV) is associated with 200,000 cancers annually, including B-cell lymphomas in immunosuppressed hosts. Hypomorphic mutations of the de novo pyrimidine synthesis pathway enzyme cytidine 5′ triphosphate synthase 1 (CTPS1) suppress cell-mediated immunity, resulting in fulminant EBV infection and EBV + central nervous system (CNS) lymphomas.

Targeted Therapies and Immune Checkpoint Inhibitors in Primary CNS Lymphoma

This review article outlines the current development of emerging treatment strategies for primary central nervous system lymphoma, a rare brain tumor with, thus far, limited therapeutic options. Small molecule targeted tyrosine kinase inhibitors, immunomodulatory agents, and immune checkpoint inhibitors will be discussed. The mechanisms of action, results of completed clinical studies, ongoing clinical trials, and future perspectives are summarized. Among the most promising clinical developments in the field of CNS lymphomas is ibrutinib, an inhibitor of Bruton’s tyrosine kinase, which relays activation of nuclear factor kappa B upon integration of constitutive B cell receptor and Toll-like receptor signals. Down-stream of nuclear factor kappa B, the thalidomide analogs lenalidomide and pomalidomide exert immunomodulatory functions and are currently explored against CNS lymphomas. Finally, immune checkpoint inhibitors, such as drugs targeting the PD-1 pathway, may become novel therapeutic options to unleash anti-tumor immunity in patients with primary CNS lymphoma.