This study is designed to test:
1. in patients with negative positron-emission tomography (PET) after 2 cycles of
BEACOPPesc chemotherapy: whether the number of cycles can be reduced without
compromising progression free survival (PFS) (2 further cycles vs. 6 further cycles)
2. for patients with positive PET after 2 cycles: whether intensifying BEACOPPesc
chemotherapy by adding Rituximab improves PFS.