 The combination of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone R-CHOP regimen has been the first-line chemotherapy for elderly patients with diffuse large B-cell lymphoma DLBCL. The treatment-related toxicities, especially the severe cardiac toxicities induced by anthracycline drugs doxorubicin, have become a major concern among elderly patients. Pegylated liposomal doxorubicin is a formulation of doxorubicin with a prolonged circulation time and unique toxicity profile. Previous single arm studies of elderly patients with lymphoma used pegylated liposomal doxorubicin instead of traditional doxorubicin in combination with rituximab, cyclophosphamide, vincristine, and prednisone the novel R-CDOP regimen, and demonstrated better safety profile, including less bone marrow suppression and less cardiac toxicities, while maintaining the efficacy. However, the efficacy and safety of these two regimens R-CHOP and R-CDOP have not been head-to-head compared in a randomized study. The aim of this study is to compare the efficacy and safety of R-CDOP rituximab, cyclophosphamide, pegylated liposomal doxorubicin, vincristine, and prednisone and R-CHOP rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone in previously untreated elderly patients with DLBCL. 