OBJECTIVE: The aim of this study was to investigate the safety and tolerability of a novel anti-folate drug, pemetrexed, in the setting of a phase I clinical trial in patients with non-HIV related central nervous system lymphoma (CNSL). METHODS: In this multicenter, open-label, phase I dose finding clinical trial, pemetrexed was investigated as a single agent treatment for primary or secondary CNSL. RESULTS: A total of 18 patients were enrolled between January 2009 and November 2014. The mean age was 64.6 years old (range: 47-79). The ratio of male to female was 1:1. One out of six patients experienced a dose limiting toxicity (DLT) at dose level 1 (600mg/m2). There were no DLTs among the four patients enrolled at dose level 2 (900m/m2). Two of six patients experienced a DLT at dose level 3 (1200mg/m2). The MTD was therefore determined to be 900mg/m2. Overall, pemetrexed was well tolerated but toxicities were seen and need to be monitored. All patients experienced at least one type of toxicity of any grade. Most patients (92.9%) experienced at least one type of neurological toxicity. Grade-3 toxicities included confusion, speech impairment, and psychosis. Twelve patients (85.7%) experienced at least one bone marrow type of toxicity of any grade. These toxicities included anemia (78.6%), thrombocytopenia (57.1%), neutropenia (50%), leukocytopenia (42.9%), and lymphopenia (42.9%). Four patients experienced either grade-3 (14.3%) or grade-4 (14.3%) neutropenia. Three patients experienced grade-3 leukopenia (21.4%). One patient experienced grade-3 lymphopenia (7.1%) and two patients experienced grade-4 lymphopenia (14.3%). Twelve patients (85.7%) experienced at least one metabolic type of toxicity of any grade. A majority of these were also grade-1 or 2, with the exception of hypophosphatemia (grade-4), hyperglycemia (grade-3) and increased ALT (grade-3), increased AST (grade-3) and increased creatinine phosphokinase (CPK) (grade-4). Constitutional and gastrointestinal symptoms were seen in >60% of patients. These consisted mainly of fatigue, constipation, nausea, and anorexia. Musculoskeletal symptoms were seen in greater than 60% of patients. Less common adverse events included pain (<60%), infection (<40%), dermatologic, ocular/visual, and pulmonary/upper respiratory (<30%). The average number of cycles on treatment for all patients was 5.5 cycles. 14 patients were evaluated for response to treatment by neuroimaging (MRI) while on treatment. Of these, four patients (28.6%) showed a complete response (CR). Of those patients, 2 patients achieved this response after only 2 doses, and 2 patients after a total of 8 doses. 5 patients (35.7%) showed a partial response (PR) and four patients (28.6%) achieved stable disease (SD). The overall response rate (ORR) was determined at 92.9% (SD, PR and CR combined). CONCLUSIONS: Given this data, pemetrexed is a powerful drug and feasible alternative to existing treatment options; however, certain toxicities need to be closely monitored. Further studies are needed to assess the efficacy of pemetrexed in a larger cohort of patients with CNSL.

L’irradiation cérébrale thérapeutique comporte un risque de neurotoxicité tardive irréversible en partie lié à l’effet de l’irradiation sur le compartiment vasculaire cérébrale. Les péricytes et les communications entre les péricytes et les cellules endothéliales jouent un rôle majeur dans la stabilisation des vaisseaux, dans la formation et la régulation de la barrière hématoencéphalique et dans le contrôle du flux sanguin cérébral. Nous montrons, dans un modèle murin d’irradiation cérébrale, que les péricytes sont une cible précoce de l’irradiation cérébrale. Après irradiation, la morphologie des péricytes est modifiée et des marqueurs d’activations du péricytes sont surexprimés. En conséquence, la communication entre péricyte et cellule endothéliale est rompue, ce qui se traduit par une diminution de la capacité du péricyte à induire une constriction vasculaire après stimulation électrique. De façon concomitante, la perméabilité de la barrière hémato-encéphalique est anormalement augmentée après irradiation. Un traitement par thalidomide, administré dans la semaine précédant et suivant l’irradiation, prévient les conséquences de l’irradiation sur les péricytes. Les communications entre péricytes et cellules endothéliales sont maintenues ainsi que les fonctions contractiles des péricytes. L’imperméabilité de la barrière hématoencéphalique est également préservée. La voie de signalisation PDGF-β/PDGFR-β essentielle au recrutement des péricytes par les cellules endothéliales, est, au moins partiellement, impliquée dans l’effet protecteur de la thalidomide. Des études supplémentaires sont nécessaires pour définir les mécanismes sous tendant l’effet de l’irradiation sur les péricytes ainsi que l’effet protecteur de la thalidomide. Nous avons en parallèle mis au point un modèle murin de lymphome cérébral luciférase positif pour vérifier, dans un premier temps, l’innocuité de l’association de la radiothérapie et de la thalidomide et de ses dérivés de la classe des immunomodulateurs (iMids), le lénalidomide et le pomalidomide. Ces trois molécules ne diminuent pas l’effet antitumoral de la radiothérapie, mais l’association de radiothérapie et de pomalidomide est synergique sur la décroissance tumorale mesurée par l’évolution des courbes de bioluminescence. Le concept de normalisation de la vascularisation tumorale fait référence aux molécules capables, non pas de faire régresser les vaisseaux tumoraux anormaux, mais de les « normaliser » pour améliorer, d’une part, la disponibilité des chimiothérapies au sein de la tumeur, et d’autre part, l’oxygénation tumorale pour accroitre l’efficacité de la radiothérapie. Nos résultats sont en faveur d’un tel effet exercé par le pomalidomide dans notre modèle murin de lymphome cérébral, caractérisé par une infiltration tumorale périvasculaire, une fuite capillaire mais sans néo angiogenèse. Nos travaux fournissent un rationnel biologique à de futurs essais cliniques avec les iMids dans le traitement des lymphomes cérébraux primitifs voire des tumeurs malignes cérébrales. / Therapeutic brain irradiation carries a risk of irreversible delayed neurotoxicity partly due to the effect of irradiation on the cerebral vascular compartment. Pericytes and communication between pericytes and endothelial cells play a major role in vessel stabilization in the formation and regulation of the blood-brain barrier and in the control of cerebral blood flow. We show in a murine model of brain irradiation, that pericytes are a target of early brain irradiation. After irradiation, the morphology of pericytes is altered and markers of activation of pericytes are overexpressed. Consequently, communication between the endothelial cell and pericyte is disrupted , which results in a decreased capacity of pericytes for inducing a vascular constriction after electrical stimulation. Concomitantly, the permeability of the blood - brain barrier is abnormally increased after irradiation. Treatment with thalidomide administered in the week before and after irradiation, prevents the effects of irradiation on pericytes . Communication between pericytes and endothelial cells are maintained as well as the contractile properties of pericytes. The impermeability of the blood brain barrier is also preserved. The PDGF-β/PDGFR-β signaling pathway, which is essential for the recruitment of pericytes by endothelial cells, is at least partially involved in the protective effect of thalidomide. Further studies are needed to define the mechanisms underlying the effect of irradiation on the pericytes and the protective effect of thalidomide. We have, in parallel, developed a model of murine luciferase positive CNS lymphoma to verify first, the safety of the combination of radiotherapy and thalidomide and its derivatives of the class of immunomodulators ( IMiDs ), lenalidomide and pomalidomide. These three molecules do not decrease the antitumor effect of radiotherapy, but the antitumoral effect of the association of radiotherapy and pomalidomide is synergistic. The concept of the normalization of the tumor vascularization refers to molecules capable not to induce regression of the abnormal tumor vessels but to "normalize" the tumoral vasculature in order to improve, on one hand , the availability of chemotherapy in the tumor , and on the other hand, the tumor oxygenation to increase the effectiveness of radiotherapy. Our results are in favor of such an effect exerted by pomalidomide in our murine model of cerebral lymphoma, characterized by perivascular tumor infiltration and capillary leak .Our work provide a biological rational for future clinical trials with IMiDs in the treatment of brain lymphomas or malignant brain tumors.

Background: Primary CNS Lymphoma is a rare and severe but potentially curable disease. In the last thirty years treatment has changed significantly. Survival times increased due to high-dose methotrexate-based chemotherapy. With intensive regimens involving autologous stem cell transplantation (ASCT), 4-year survival rates of more than 80% can be reached. However, this treatment regimen is not feasible in all patients, and is associated with some mortality. Methods: In this review, current evidence regarding the efficacy and toxicity of radiotherapy in PCNSL shall be summarized and discussed mainly based on data of controlled trials. Results: Being the first feasible treatment whole brain radiotherapy (WBRT) was initially used alone, and later as a consolidating treatment after high-dose methotrexate-based chemotherapy. More recently, concerns regarding activity and neurotoxicity of standard dose WBRT limited its use. On the contrary, latest evidence of some phase II trials suggests efficacy of consolidating WBRT is comparable to ASCT. After complete remission reduced dose WBRT appears as a feasible concept with decreased neurotoxicity. Evidence for use of local stereotactic radiotherapy is very limited. Conclusion: Radiotherapy has a role in the treatment of PCNSL patients not suitable to ASCT, e.g., as consolidating reduced dose WBRT after complete response. Local stereotactic radiotherapy for residual disease should be examined in future trials.