275P - Primary central nervous system lymphoma treated with high-dose methotrexate and rituximab: Preliminary results in Vietnam

Abstract

BackgroundCurrent treatment for primary central nervous system lymphoma involves high-dose methotrexate based regimen. In low&middle-income countries like Vietnam, a shortage of drugs and monitoring is common. The present study reports the first experience and preliminary results of 25 patients PCNSL treated with HD-MTX and RTX. MethodsFollowing Institutional Review Board approval by Vietnam National Institute for Cancer Control, a prospective study evaluating the treatment of histologically confirmed PCNSL with combined biweekly HD-MTX (8g/m2/dose) and weekly RTX (375 mg/m2/dose) for 8 cycles. Responders received consolidation treatment with 2 additional cycles, followed by maintenance with monthly HD-MTX for up to 12 months. Patients received aggressive hydration infusion to maintain a urine output of ≥ 100 ml/h and a urinary pH of > 7, until serum MTX levels had decreased to ≤ 0.1 µM/l. Serum MTX levels were monitored daily. Leucovorin rescue was initiated 24 h after completion of MTX infusion and administered at 50 mg IV every 6 h for the first 4 doses and then 30 mg IV until serum MTX levels were ≤0.1 µM/l. Leucovorin dosing was increased in cases of slow MTX clearance. The primary end point was radiographic response, and drug-related toxicity and secondary were survival. ResultsFrom 01/2017 to 12/2018, 25 patients were analysed (13 males and 12 females, median age 58.6). Following a mean of 10,72 cycles, the response rate and CR rate was 88% and 36%. The median PFS was 13 months and the OS has not yet been attained. MTX clearance was achieved by 72h in 198/268 cycles, and by 96h in 92%; 30.9% cycles needed escalation of leucovorin rescue dose. Toxicity: transient transaminitis (72%), mucotitis (59%) and diarhea (61.9%), febrile neutropenia (8%). Pneumonia was observed in 2 patients. 4 patients had renal dysfunction and 2 patient had dialysis. ConclusionsRTX combined HDMTX for PCNSL is possible in lower-middle income countries like Vietnam but should be done in experienced centers capable of close monitoring serum MTX levels to prevent toxicity. The addition of RTX to HD-MTX in the treatment of PCNSL may increase response rates and prolong PFS. The final results currently in progress will more definitively estimate the survival. Legal entity responsible for the studyThe authors. FundingHas not received any funding. DisclosureAll authors have declared no conflicts of interest.