DURATION OF THERAPY Therapy in LCCC 1637 involves up to 6 cycles of treatment with brentuximab vedotin (BV) with a chemotherapy treatment made up of cyclophosphamide, doxorubicin, etoposide, and prednisone (CHEP). Each cycle is 21 days long. Participants may continue on BV alone as maintenance therapy after 6 cycles of BV-CHEP if they meet the requirements outlined above. Each cycles of BV maintenance therapy is 21-day long. BV maintenance therapy may continue until a participant's disease progresses.