Impact of thiotepa dose-intensity in primary diffuse large B-cell lymphoma of the central nervous system undergoing autologous hematopoietic cell transplant with thiotepa/carmustine conditioning

Thiotepa/carmustine (TT-BCNU) is a commonly used autologous transplant (ASCT) conditioning regimen for primary DLBCL of the CNS (PCNSL). The total thiotepa dose varies among TT-BCNU recipients, with some centers administering a total dose of 20 mg/kg, while others using 10 mg/kg. We retrospectively assessed the impact of thiotepa dose intensity on ASCT outcomes in 218 adult PCNSL patients who underwent a first ASCT with TT-BCNU conditioning and received either a total thiotepa dose of 10 mg/kg (TT-10 group; N = 90), or 20 mg/kg (TT-20 group; N = 128). The median follow-up of survivors was 22 months. The cumulative incidence of 1-year non-relapse mortality (NRM) for TT-10 and TT-20 cohorts were 6% (95%CI = 2–12%) vs. 4% (95%CI = 1–8%), respectively (p = 0.66). The 3-year cumulative incidence of relapse (15% vs. 13%; p = 0.67), progression-free survival (PFS) (71% vs. 80%; p = 0.25) and overall survival (OS) (79% vs. 83%; p = 0.56) were similar in the TT-10 and TT-20 groups, respectively. On multivariate analysis compared to TT-10, the TT-20 cohort was not associated with significantly different risk of NRM (Hazard ration [HR] = 0.77; p = 0.64), relapse/progression (HR = 0.87; p = 0.74), PFS (HR = 0.80; p = 0.48) or OS (HR = 1.10; p = 0.80). In conclusion thiotepa dose-intensity in TT-BCNU conditioning does not impact ASCT outcomes of PCNSL patients.