After the completion of induction chemotherapy, patients undergo CT scan and positron emission tomography (PET) scanning. If the PET scan is positive in one or more nodal sites, a repeat biopsy is performed. Patients with a negative PET scan OR a negative repeat biopsy (including no evidence of lymphoma on repeat bone marrow biopsy) are assigned to receive regimen A for consolidation therapy. Patients with a positive repeat biopsy are assigned to receive regimen B for consolidation therapy.