 I. To compare the event-free survival of rituximab, cyclophosphamide, doxorubicin hydrochloride, vincristine sulfate, prednisone R-CHOP versus dose-adjusted DA- etoposide, prednisone, vincristine sulfate, doxorubicin hydrochloride, cyclophosphamide, and rituximab EPOCH-R chemotherapy in untreated cluster of differentiation CD20 positive diffuse large B-cell lymphomas. 