Role of chemotherapy additional to high-dose methotrexate for primary central nervous system lymphoma (PCNSL)

Abstract

Primary central nervous system lymphoma (PCNSL) is a variant of extranodal non-Hodgkin lymphoma (NHL) that accounts for about 2% to 5% of all primary intracranial tumours with immunocompetent patients. It appears at a median age of 62 years. A standard of care for PCNSL patients has not been defined yet, but high-dose methotrexate (HD-MTX) is considered to be a beneficial chemotherapy in PCNSL treatment. Currently, HD-MTX is combined with numerous other chemotherapy drugs to improve outcomes of HD-MTX monotherapy. However, the impact of additional chemotherapy remains unclear, as there is evidence of a higher risk of adverse events (AEs) such as infective complications. We performed a systematic review of randomised controlled trials (RCTs) to assess the efficacy and safety of additional chemotherapy to HD-MTX in the treatment of immunocompetent PCNSL patients. We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 5) and MEDLINE (from 1950 to May 2012) as well as conference proceedings for RCTs. Two review authors (NB, NS) independently screened search results. We included RCTs comparing HD-MTX in combination with additional chemotherapy to mono-chemotherapy with HD-MTX in immunocompetent patients off all ages in first-line treatment of PCNSL. As an effect measure we used hazard ratios (HR) and 95% confidence intervals (CI) for overall survivals (OS) and progression-free survival (PFS). For effect measure of complete remission rate (CRR), partial response rate (PRR), treatment-related mortality (TRM) and AEs we used risk ratios (RR). Two review authors (NB, NS) independently extracted data and assessed the quality of trials. Our search strategies led to 699 potentially relevant references. Of these, one RCT involving 79 patients was included. We judged the quality of the trial as moderate. The study was reported as a randomised open-label study and published as a full-text article.Even though PFS was statistically significantly improved for patients treated with HD-MTX plus cytarabine (HR 0.54; 95% CI 0.31 to 0.92; P = 0.01), this did not translate to a statistical significant OS benefit (HR 0.65; 95% CI 0.38 to 1.13; P = 0.07). AEs, especially infective complications, hepatotoxicity and haematological toxicities, were assessed more often in patients undergoing HD-MTX therapy combined with cytarabine. However, there were no statistically significant differences in terms of TRM (RR 3.08; 95% CI 0.33 to 28.32; P = 0.35). Owing to the small number of included trials and patients, the findings in this review remain uncertain. In summary, the presently available evidence (one small trial) showed a benefit in terms of PFS, ORR and CRR but no statistically significant difference regarding OS for patients with PCNSL treated with HD-MTX plus cytarabine compared to HD-MTX alone. However, the risk of severe infections and toxicity was significantly higher in patients treated with combined chemotherapy. More RCTs with additional chemotherapy to HD-MTX therapy with higher numbers of patients and longer follow-up periods are needed to confirm the results of this review and determine whether the PFS benefit will translate into an OS advantage. At least the one included study shows that RCTs of moderate quality and with valuable outcomes for this malignant disease are feasible.