High-Dose Chemotherapy and Autologous Stem-Cell Transplantation for Primary CNS Lymphoma: Updated Results from a Pilot and Phase II Study

Introduction: High-dose chemotherapy (HDT) and autologous stem-cell transplantation (ASCT) demonstrated high efficacy in the treatment of newly-diagnosed primary CNS lymphoma (PCNSL) in younger patients (pts.). A 5-year overall survival probability (OS) of 69% could be demonstrated in 30 pts within a phase-II trial on HDT and ASCT with consolidating whole-brain-irradiation (WBRT) (Illerhaus et al. JCO 2006). A subsequent pilot trial on HDT and ASCT without WBRT showed a 5-year OS of 77% (Illerhaus et al. Haematologica 2008). Here we give an update of our two different treatment regimens and future perspectives.

Patients and Methods: Thirty pts. ≤65 years were treated within the phase II trial, chemotherapy (CHT) consisted of 3 cycles of high-dose methotrexate (MTX, 8 g/m²), 1 cycle of AraC (2× 3 g/m²) plus thiotepa (TT, 40 mg/m²) followed by rG-CSF and stem-cell-mobilization. Conditioning regimen included BCNU (400 mg/m²) and TT (2×5 mg/kgBW) followed by ASCT. Hyperfractionated WBRT (45 Gy, 2×1Gy/d) was administered as consolidation. In our subsequent pilot trial 13 pts. (age 38–67 years) were treated without consolidating WBRT; CHT was intensified with 4 cycles MTX 8g/m², 2 cycles AraC (2× 3 g/m²) and TT (40 mg/m²). Dose escalated HDT included BCNU (400 mg/m²) and TT (4×5 mg/kgBW) followed by ASCT. WBRT was reserved for pts. not responding to CHT.

Results: Median follow-up of the 30 pts. treated within our phase II trial was extended to 95 months (mo), the updated 5-year OS of all pts. is 66.6% and 82,3% of the subgroup of pts. who underwent HDT and ASCT (n=23), respectively. Three additional deaths occurred due to relapse (n=2) after 45 and 71 mo and due to comorbidity (n=1) after 103 mo. Five of 30 pts. developed severe leukoencephalopathy during follow-up. With a median follow-up of 35 mo in the 13 pts. treated within the pilot-phase without consolidating WBRT 3-year OS of all pts. is 77%. No further relapse or non-relapse mortality occurred in this pilot-group during. Most recent follow-up data will be presented in detail.

Conclusion: Sequential systemic application of high-dose cytostatic agents followed by HDT+ASCT is highly effective as initial therapy for pts. with PCNSL. The restriction of WBRT to refractory disease shows similar OS rates and a decrease in neurotoxicity. In an ongoing multicenter phase-II trial immunotherapy with rituximab is combined with HDT and ASCT to further increase remission rates. A future randomized trial should be focused on the efficacy of consolidation with HDT supported by ASCT.