Early response to high-dose methotrexate, vincristine, and procarbazine chemotherapy-adapted strategy for primary CNS lymphoma: no consolidation therapy for patients achieving early complete response.

Optimal treatment strategies for primary central nervous system lymphoma (PCNSL) have not been established. In this study, we investigated the treatment outcomes and prognostic factors of high-dose methotrexate, vincristine, and procarbazine (MVP) chemotherapy followed by an interim response-adapted intensification strategy in immunocompetent patients with PCNSL. We evaluated the evidence of infection with Epstein-Barr virus (EBV) in both brain tumor tissue and whole blood. Forty patients were retrospectively reviewed. Ten (25 %) patients who achieved complete response (CR) in the interim analysis did not receive any additional consolidation treatment after completion of planned high-dose MVP chemotherapy. Additional radiotherapy (n = 9) or autologous stem cell transplantation (ASCT) (n = 7) was performed in patients who did not achieve CR in the interim analysis. The median age was 55 years. The overall CR rate was 62.5 % (n = 25), and the objective response rate was 75.0 %. Two-year overall survival (OS) was 59.8 %, and 2-year progression-free survival was 47.1 %. Grade 3 or 4 neutropenia and thrombocytopenia occurred in 47.5 and 32.5 % of patients, respectively. Treatment-related mortality was 15.0 % (n = 6), and four patients developed delayed neurotoxicity. There was no evidence of EBV-encoded RNA expression in brain tumor tissue. Ten (29.4 %) of 34 patients showed detectable EBV-DNA in whole blood. Poor performance status and EBV-DNA positivity in whole blood were significantly associated with inferior OS (p = 0.032, p = 0.023, respectively). We suggest that high-dose MVP chemotherapy followed by an early response-adapted intensification strategy may be effective and minimize the number of patients who receive radiotherapy or ASCT in the early course of treatment.