A Study to Evaluate the Safety and Efficacy of Glofitamab in Combination With Rituximab (R) Plus Cyclophosphamide, Doxorubicin, Vincristine, and Prednisone (CHOP) in Circulating Tumor (ct)DNA High-Risk Patients With Untreated Diffuse Large B-Cell Lymphoma

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): 2-5 * 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, T-cell/histiocyte-rich 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