Outcomes of a non-thiotepa conditioning regimen with BuCyE and ASCT for CNS lymphoma: A series of three patients

Lymphoma of the central nervous system (CNS) forms a rare type of lymphoma with a poor prognosis. Chemo-immunotherapy containing a methotrexate backbone remains the treatment of choice in the first line setting. When responses are achieved, this treatment needs to be followed, whenever possible, by treatment intensification followed by autologous stem cell transplantation (ASCT). There is no consensus on the optimal conditioning regimen for ASCT. Most studied regimens contain thiotepa, an agent that can cross the blood brain barrier, which confer excellent survival outcomes. However, this drug is not widely accessible in the United States for multiple reasons. An alternative to thiotepa-based regimens is the combination of busulfan, cyclophosphamide, and etoposide (BuCyE), which has resulted in conflicting outcomes. Here we report our experience with 3 cases of CNS lymphoma, treated with BuCyE, with a protocol using dosages different from what was previously reported, specifically with busulfan 3.2 mg/kg at days -8 to -5 (with pharmacokinetics adapted dosing at days -6 and -5), etoposide 30 mg/kg on day -4, and cyclophosphamide 60 mg/kg on day -3. Treatment resulted in excellent long-term outcomes with all 3 patients being alive at least 4 years following ASCT with no evidence of relapse. The side effect profile was acceptable, with the exception of a case of pulmonary toxicity. This cohort is limited by its small size, and further work comparing it to other treatments is being done at our institution.