ML-08 THE ROLE OF MAINTENANCE HIGH-DOSE METHOTREXATE CHEMOTHERAPY IN ELDERLY PRIMARY CNS LYMPHOMA PATIENTS

BACKGROUND: The addition of high-dose methotrexate (HD-MTX)-based chemotherapy to whole brain irradiation (WBRT) has improved the prognosis of primary central nervous system lymphoma (PCNSL). However, the high neurotoxicity rates observed, especially in the elderly, raised interest in chemotherapy-only treatments. Withholding radiotherapy substantially decreases the risk of neurotoxicity, however, disease control may be compromised. In the elderly who cannot tolerate WBRT as a consolidation, maintenance treatment may serve as a feasible approach after an initial response. We treated ePCNSL with induction immunochemotherapy, maintenance chemotherapy with HD-MTX and deferred WBRT. Here, we retrospectively investigated the prognosis for ePCNSL that became CR after the induction chemotherapy. MATERIAL AND METHODS: Newly diagnosed ePCNSL (median age: 74 years) received biweekly rituximab/HD-MTX for 6 cycles (induction) followed by monthly rituximab/HD-MTX for 2 cycles (consolidation) and then were treated differently according to the radiological response. With CR patients, HD-MTX was continued with every 3 months (maintenance) for 2 years. Patients who did not obtain consent for maintenance therapy were followed up. For PD patients, immunochemotherapy was interrupted and WBRT initiated immediately. Patients with PR and SD were treated with alternative chemotherapy with temozolomide and/or stereotactic radiotherapy or WBRT. RESULTS: The median PFS was 24.6 months and median OS was 27 months for the entire cohort. Of the 42 ePCNSL, 26 had CR after induction and consolidation, of which 18 cases were carried out maintenance (M+) and 8 cases were followed up (M-). Median PFS was 73 months in the M+ group and 24.5 months in the M- group. Median OS is 102.2months versus 27.6 months, respectively. Both mPFS (P= 0.0125) and mOS (P =0.0015) were significantly prolonged by maintenance therapy. CONCLUSION: It was suggested that maintenance treatment with HD-MTX may improve the prognosis for ePCNSL that reached complete response after induction therapy.