A Study on Pharmacokinetics (PK), Efficacy and Safety of Subcutaneous (SC) Versus Intravenous (IV) Rituximab, in Combination With CHOP (Cyclophosphamide, Doxorubicin, Vincristine, Prednisone) in Previously Untreated Participants With CD20 Positive Diffuse Large B-Cell Lymphoma (DLBCL)

Inclusion Criteria: * Previously untreated CD20 positive diffuse large B-cell lymphoma (DLBCL) * Participants with an International Prognostic Index (IPI) score of 1 to 5 or IPI score of 0 with bulky disease, defined as one lesion \>/=7.5 cm * At least one bi-dimensionally measurable lesion defined as \>/=1.5 cm in its largest dimension on CT scan * Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2 * Left ventricular ejection fraction (LVEF) \>/=50% on cardiac multiple-gated acquisition (MUGA) scan or cardiac echocardiogram * A negative serum pregnancy test or a negative urine pregnancy test within 7 days prior to study treatment * For men who are not surgically sterile, agreement to use a barrier method of contraception during the treatment period and until \>/=12 months after the last dose of rituximab SC or rituximab IV or according to institutional guidelines for CHOP chemotherapy, whichever is longer, and agreement to request that their partners use an additional method of contraception * For women of reproductive potential who are not surgically sterile, agreement to use adequate methods of contraception during the treatment period and until \>/=12 months after the last dose of rituximab SC or rituximab IV or according to institutional guidelines for CHOP chemotherapy, whichever is longer * Adequate hematologic function confirmed within 14 days prior to randomization Exclusion Criteria: * Transformed non-Hodgkin's lymphoma (NHL) or types of N…