Constant pattern of relapse in primary central nervous lymphoma patients treated with high-dose methotrexate combinations. A Finnish retrospective study.

Primary central nervous system lymphoma (PCNSL) is a rare brain tumour with a dismal prognosis. Several phase II studies with high-dose methotrexate-based regimens have shown promising early results, but in all hospital-based data published so far, the disease outcome is poor.We performed a hospital-based retrospective analysis to evaluate the long-term results of the Nordic type of Bonn chemotherapy regimen in PCNSL patients. The study included 54 patients with newly diagnosed PCNSL who received chemotherapy with curative intent as their first-line treatment.We found promising response rates, 76% of the patients achieving CR and 22% patients achieving PR, with corresponding two-year EFS 53% and OS 76%. However, with longer follow-up a constant pattern of relapses was observed with only one patient remaining in primary remission after 60 months.The finding suggests that basic biological differences exist between PCNSL and systemic diffuse large B-cell lymphoma and there is a need for consolidation or maintenance therapy after achieving a remission in patients with PCNSL.