Arm B (experimental intervention)
Patients in the experimental arm will receive 2 cycles of R-MTX/AraC (rituximab 375 mg/m² i.v. d0, 4; MTX 3,5 g/m² i.v. d1, AraC 2 × 2 g/m²/d i.v. d2 + 3) every 3 weeks followed by consolidating HCT-ASCT with rituximab 375 mg/mStem cell harvest will be performed after cycle 1 of MARTA according to local standard procedure. In case of unsuccessful stem cell harvest after cycle 1, stem cell harvest can be performed after cycle 2.