Cyclophosphamide, doxorubicin, vincristine, prednisolone (CHOP) versus cyclophosphamide, epirubicin, vincristine, prednisolone, ifosfamide, VP-16, methotrexate, dexamethasone (CEOP/IMVP-Dexa) for aggressive non-Hodgkinxxxs lymphoma. A multicenter randomized trial of the Austrian working party medical oncology.