Relapse pattern and prognosis of primary CNS lymphoma.

TO THE EDITOR: We compliment the work of Kim et al., on relapse patterns and prognosis of primary CNS lymphoma (PCNSL) [1]. Analyzing data on 65 patients with newly diagnosed PCNSL, authors conclude that regular systemic evaluation of extra-cranial site may not always be necessary. They also report that age less than 60 to have better overall survival (OS) and patients who received chemotherapy followed by autologous stem cell transplantation (Ctx-ASCT) to have better failure free survival (FFS). This study is one of the few studies to analyze PCNSL relapse patterns and the first study so far to analyze impact of Ctx-ASCT as compared to other treatment options in PCNSL.

Ctx-ASCT is an established therapy in systemic non-Hodgkin lymphomas; however it still remains an investigational treatment option in PCNSL especially in upfront setting [2]. There have been only a handful of clinical trials evaluating high dose chemotherapy followed by ASCT as a first line therapy in PCNSL patients. The results from those studies are encouraging; however, selection bias appears to be concerning. Most of the studies have selectively recruited younger patient with good performance status. Also exclusion of patients who were chemorefractory to high dose chemotherapy from receiving ASCT adds to the selection bias. Authors do provide baseline characteristics of the whole cohort; however it is of vital importance to know about characteristics of patients receiving Ctx-ASCT to draw any clinical conclusions.

Another important observation in this study, which deserves mention, is comparison of response rates of Ctx-ASCT and Ctx followed by whole brain radiation therapy (WBRT). It is well established now that high dose methotrexate based regimens forms the backbone of PCNSL treatment; however, the best therapy to consolidate the initial response is still debatable [3]. WBRT provides good results but at the cost of increased risk of neurotoxicity. There is growing body of evidence, which suggests that ASCT could be used as consolidation therapy [4]. In this study, overall response rate for Ctx-ASCT was higher than Ctx-WBRT (90% as opposed to 86%). But it would be important to know, if patient characteristics were similar for both the treatment regimens or not.