Autologous stem cell transplantation with thiotepa, busulfan, and cyclophosphamide conditioning in patients with...

The prognosis of central nervous system lymphoma (CNSL) remains poor, and attempts have been made to improve outcomes through autologous stem cell transplantation (ASCT) with thiotepa-based conditioning. We aimed to assess the outcomes of thiotepa/busulfan/cyclophosphamide (TBC) followed by ASCT in CNSL. An investigator-initiated, single-arm, phase II trial was conducted to evaluate the efficacy and safety of TBC/ASCT (NCT06625359). The conditioning dose was adjusted based on age and performance status (9-day or 8-day regimen). As this trial was terminated early after enrolling 17 patients, a retrospective cohort of CNSL treated with the same protocol was included. In total, 44 patients were included in the study and classified into 8-day and 9-day groups according to the TBC regimen received. In total, 25 patients (56.8%) had primary CNSL, and 19 patients (43.2%) received the 9-day regimens. Following ASCT, 33 patients (75.0%) achieved an objective response (32 complete response and 1 partial response). The 3-year progression-free survival (46.5% vs. 52.6%, P = 0.49) and overall survival (60.5% vs. 73.7%, P = 0.77) for 8-day and 9-day groups were comparable. The 1-year cumulative incidence of non-relapse mortality in the 8-day group showed a trend toward decrease compared to that in the 9-day group (4.6% vs. 21.1%, P = 0.073). Our study demonstrates the efficacy of TBC/ASCT in CNSL in the Asian population. The conventional busulfan dose (9-day regimen) may be associated with higher toxicity, suggesting the potential need for a modified TBC regimen in Asian populations. Further studies are needed to identify the optimal thiotepa-based conditioning in CNSL.