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.

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.