Adverse events

INDUCTION: Patients receive cyclophosphamide IV and doxorubicin IV on day 1, etoposide IV on days 1-3, and prednisone PO on days 1-5. Patients also receive brentuximab vedotin IV over approximately 30 minutes on day 1. Treatment repeats every 21 days for up to 6 cycles (or for up to 5 cycles for patients who received 1 cycle of CHOP-like or CHP-BV therapy prior to induction, per investigator's discretion) in the absence of disease progression or unacceptable toxicity. CONSOLIDATION: Between 30-60 days post-consolidative autologous stem cell therapy, post-consolidative radiation therapy, or after completing induction cycle 6 (cycle 5 for patients who qualify for receiving 5 cycles of CHEP-BV instead of 6), patients with objective response (complete response or partial response) receive brentuximab vedotin IV over approximately 30 minutes on day 1. Treatment repeats every 21 days for up to 10 cycles in the absence of disease progression or unacceptable toxicity. Brentuximab Vedotin: Given IV Cyclophosphamide: Given IV Doxorubicin: Given IV Doxorubicin Hydrochloride: Given IV Etoposide: Given IV Etoposide Phosphate: Given IV Laboratory Biomarker Analysis: Correlative studies Prednisone: Given PO