ML-8 HIGH-DOSE CHEMOTHERAPY SUPPORTED BY AN AUTOLOGOUS STEM CELL TRANSPLANT IN RELAPSED PRIMARY CNS LYMPHOMA

BACKGROUND: Many patients with primary CNS lymphoma (PCNSL) relapse despite complete response (CR) after initial therapy. Relapsed PCNSL (rPCNSL) has a poor prognosis, and no adequate standard of treatment has been established. Autologous stem cell transplant (ASCT)-assisted high-dose chemotherapy (HDC) for rPCNSL is a promising treatment option, as is thiotepa (TT), which has been used in malignant lymphoma as a treatment option for PCNSL. In March 2020, TT was approved in Japan as a pre-treatment for ASCT in malignant lymphoma. TBC, TT with busulfan and cyclophosphamide, and BCNU+TT are used in Europe and the US, but treatment-related mortality (TRM) has been reported in about 10% of patients. The regimen approved in Japan is Buslufan-TT(BuTT) therapy in combination with busulfan, which differs from TBC in dosage, and there is little information on efficacy and safety for rPCNSL. In our hospital, we have introduced BuTT therapy for rPCNSL in patients under 65 years of age. In this report, we describe our experience with this treatment. Subjects: Five patients with rPCNSL since May 2021, age <66 years, PS 0-2, are included in this study. METHODS: After obtaining CR with (R)MPV therapy after relapse, peripheral blood stem cells were harvested after administration of G-CSF and plerixafor, pretreated with BuTT therapy (Bu: 3.2 mg/kg, Day-8, -7, -6, -5: TT: 5 mg/kg, Day-4, -3) and transplanted on Day 0. RESULTS: Adverse events of Grade 3 or higher were abdominal pain in 2 cases, diarrhea in 1 case, pharyngitis in 2 cases, sepsis in 1 case, and pleuritis in 1 case, but all recovered, and no TRM was observed. All five patients are currently alive without recurrence. CONCLUSION: HDC/ASCT is expected to be a curative treatment for rPCNSL. Future issues include the establishment of an upper age limit for the indication.