Favorable Outcomes with Thiotepa/Busulfan-Based Conditioning and Autotransplant for Patients with Aggressive B-Cell Lymphoma and Secondary CNS Involvement
Authors: Puckrin Robert , Chua Neil , Shafey Mona , Stewart Douglas A. 
Published: November 2021

Abstract
Introduction : Central nervous system (CNS) relapse is a devastating complication affecting ~5% of patients with diffuse large B-cell lymphoma (DLBCL). The optimal management is unknown and survival rates are ~20% in contemporary series. Thiotepa/busulfan-based high-dose chemotherapy (HDT) and autotransplant (ASCT) has demonstrated efficacy in primary CNS lymphoma, but there have been fewer studies of this conditioning regimen in secondary CNS lymphoma (SCNSL).
Methods : This multicenter retrospective study included all consecutive patients ≥18 years old with aggressive B-cell lymphoma and secondary CNS involvement treated with thiotepa/busulfan-based HDT/ASCT at the University of Calgary and University of Alberta since 2005. Kaplan-Meier curves were used to estimate progression-free survival (PFS), overall survival (OS), and disease-specific survival (DSS) from the time of ASCT. Data collection is underway for all consecutively diagnosed SCNSL patients at our institutions to evaluate frequency and predictors of HDT/ASCT use.
Results : This study included 57 patients with DLBCL (n=45), double-hit lymphoma (n=6), high-grade B-cell lymphoma NOS (n=2), intravascular large B-cell lymphoma (n=2), or T-cell/histiocyte-rich large B-cell lymphoma (n=2). Two (4%) had previously treated indolent B-cell lymphoma and 1 (2%) had multiply relapsed DLBCL. Median International Prognostic Index was 4 (range 0-5) at DLBCL diagnosis and median time to CNS relapse was 4 months (range 0-139). Median age was 58 years (range 20-73) and median ECOG was 3 (range 0-4) at diagnosis of SCNSL. CNS involvement was present at initial diagnosis in 20 (35%) patients or developed during frontline treatment in 10 (18%) or after completion of treatment in 27 (47%). For those without SCNSL at diagnosis, isolated CNS relapse occurred in 31 (84%) patients while 6 (16%) had concurrent CNS and systemic relapse.
Most patients (n=54, 94%) received high-dose methotrexate (HD-MTX)-based multiagent induction chemotherapy (median HD-MTX doses 4, range 1-5) followed by peripheral blood stem cell mobilization with rituximab, dexamethasone, cytarabine, and cisplatin (R-DHAP) in 41 (72%). HDT conditioning regimens were thiotepa, busulfan, melphalan, rituximab (TBMR, n=52, 91%) or thiotepa, busulfan, cyclophosphamide (TBC, n=5, 9%). Median time from SCNSL diagnosis to ASCT was 116 days (range 7-201). Median time to neutrophil engraftment was 10 days (range 7-15) and to platelet engraftment 16 days (range 9-93).
Overall response rates (ORR) for systemic/CNS disease were 93%/89% pre-ASCT and 95%/100% post-ASCT. Combined ORR pre-ASCT was 88%, with complete response in 21% and partial response in 67%. Two (4%) patients who developed CNS relapse immediately prior to ASCT achieved long-term remission after TBMR conditioning without any other systemic chemotherapy. With a median follow-up time of 4.0 years (range 0.1-15.9), PFS was 75% (95% CI 61-85%), OS was 76% (95% CI 62-86%), and DSS was 79% (95% CI 64-88%) at 4 years after ASCT. Lymphoma recurred in 9 (16%) patients at median 88 days (range 54-346) after ASCT with CNS relapse (n=4), systemic relapse (n=3), or both (n=2). There were 2 (4%) deaths due to peri-transplant toxicity and 1 (2%) death at 1.5 years due to therapy-related acute myeloid leukemia; no other unexpected toxicities of HDT/ASCT were observed. Among the 45 (79%) patients achieving long-term disease-specific survival, none were treated with CNS radiation therapy and only 1 (2%) had persistent neurocognitive impairment. There were no significant differences in DSS with respect to timing of CNS relapse, concurrent presence of systemic disease, or TBMR versus TBC conditioning (78% vs 80%, p=0.87).
Conclusion : In one of the largest studies of this conditioning regimen in SCNSL to date, we found that high-dose thiotepa/busulfan-based conditioning with ASCT is associated with favorable outcomes for patients with aggressive B-cell lymphoma and secondary CNS involvement, with 4-year OS ~75% in this study. Although SCNSL has been historically associated with a poor prognosis, an increasing proportion of patients may achieve long-term survival after intensive therapy with HD-MTX-based induction and thiotepa/busulfan-based HDT and ASCT.
Figure 1 Figure 1.

Disclosures
Chua: Eisai: Honoraria; Pfizer: Honoraria; Merck: Honoraria; Gilead: Honoraria. Stewart: Novartis: Honoraria; AstraZeneca: Honoraria; Amgen: Honoraria; Celgene: Honoraria; Gilead: Honoraria; Abbvie: Honoraria; Janssen: Honoraria; Roche: Honoraria; Sandoz: Honoraria; Teva: Honoraria.