Inclusion Criteria:

          -  Previously untreated patients with CD20-positive DLBCL, including one of the following
             diagnoses made according to the 2016 World Health Organization (WHO) classification of
             lymphoid neoplasms

               -  DLBCL, not otherwise specified, including GCB and ABC/non-GCB types as well as
                  double-expressor lymphoma (coexpression of MYC and BCL2)

               -  High-grade B-cell lymphoma (HGBCL) with MYC and BCL2 and/or BCL6 translocations

               -  Patients with de novo transformed follicular lymphoma (patients with discordant
                  bone marrow involvement, i.e., evidence of low-grade histology in bone marrow)
                  may be considered after discussion with the Medical Monitor

          -  Eastern Cooperative Oncology Group (ECOG) Performance Status of 0-2

          -  International Prognostic Index (IPI): 1-5

          -  Life expectancy of at least 6 months

          -  Adequate biomarker blood samples prior to initiation of R-CHOP on Day 1 of Cycle 1 and
             on Day 1 of Cycle 2 submitted for screening for determination of ctDNA status

          -  At least one bi-dimensionally fluorodeoxyglucose (FDG)-avid measurable lymphoma lesion
             on positron emission tomography/computed tomography (PET/CT) scan

          -  Left ventricular ejection fraction (LVEF) >=50%, as determined on cardiac
             multiple-gated acquisition (MUGA) scan or cardiac echocardiogram (ECHO)

          -  Adequate hematopoietic function

          -  Contraception use

        Additional Inclusion Criterion for ctDNA High-Risk Participants:

          -  Plasma sample evaluated to be ctDNA high risk

        Exclusion Criteria:

          -  Current diagnosis of B-cell lymphoma, unclassifiable, with features intermediate
             between DLBCL and classic Hodgkin lymphoma (gray-zone lymphoma), primary mediastinal
             (thymic) large B-cell lymphoma, Burkitt lymphoma, central nervous system (CNS)
             lymphoma (primary or secondary involvement), primary effusion DLBCL, and primary
             cutaneous DLBCL

          -  Contraindication to any of the individual components of R-CHOP, including prior
             receipt of anthracyclines, history of severe allergic or anaphylactic reactions to
             murine monoclonal antibodies, or known sensitivity or allergy to murine products

          -  Prior treatment for indolent lymphoma

          -  Prior solid organ or allogeneic stem cell transplant

          -  Prior therapy for DLBCL and high-grade B-cell lymphoma (HGBCL) with the exception of
             palliative, short-term treatment with corticosteroids

          -  Pregnant or breastfeeding, or intending to become pregnant during the study or within
             12 months after the final dose of R-CHOP, 3 months after the final dose of tocilizumab
             (if applicable), or 2 months after the final dose of glofitamab