The Feasibility and Clinical Efficacy of Atezolizumab Consolidation Treatment in High Risk (IPI > 2) DLBCL

Inclusion Criteria: * Age 18-75 (inclusive) years * Patients with a confirmed histologic diagnosis of diffuse large B-cell lymphoma (DLBCL-NOS) based upon a representative histology specimen according to the World Health Association (WHO) classification, revision 2016 * Ann Arbor stages II-IV * WHO performance status 0 - 1 * International Prognostic Index (IPI) ≥ 3 at diagnosis * Complete metabolic remission (Deauville 1-3) after 6-8 cycles of R-CHOP according to the Lugano criteria Of note: 1. Rituximab may have been administered either intravenously or subcutaneously. A rituximab biosimilar may have been used when it is approved for the indication of DLBCL. 2. Patients should have received at least 6 cycles R-CHOP. Dose reductions for vincristine are allowed during R-CHOP. Dose reductions because of bone marrow toxicity are allowed but cannot exceed \>15% of cumulative dose of doxorubicin and cyclophosphamide. 3. Central nervous system prophylaxis (MTX) by intrathecal therapy or IV is allowed. 4. Fludeoxyglucose Positron Emission Tomography (18F-FDG-PET) scan should have been made 4-8 weeks after last induction cycle 5. Histologically confirmed false positive EoT PET-scans are eligible. * Negative pregnancy test at study entry * Patient is willing and able use adequate contraception during and until 5 months after the last protocol treatment. * Patient is capable of giving a written informed consent Exclusion Criteria: Diagnosis • All histopathological diagnoses other than DLBCL-NOS according to the WHO classification, revision 2016, including: \- High-grade B-cell lymphoma with a double/triple translocation with MYC, BCL2 and/or BCL6. Please note that patients with an isolated MYC translocation or an isolated BCL2 translocation or an isolated BCL-6 translocation are eligible (single hit translocation). * Testicular large B-cell lymphoma * Primary mediastinal B cell lymphoma * Transformed indolent lymphoma * Post-transplant lymphoproliferative disorder Organ dysfunction * Clinical signs of severe pulmonary dysfunction * Clinical signs of heart failure (New York Heart Association (NYHA) classification II-IV) * Symptomatic coronary artery disease or cardiac arrhythmias not well controlled with medication. * Myocardial infarction during the last 6 months * Significant renal dysfunction (serum creatinine ≥ 150 umol/l or clearance ≤ 30ml/min Creatinine clearance (CrCl) may be calculated by Cockcroft -Gault formula: CrCl = (140 - age \[in years\]) x weight \[kg\] (x 0.85 for females)/(0.815 x serum creatinine \[μmol/L\]) • Inadequate hematological function: hemoglobin \< 5.5 mmol/L Absolute Neutrophil Count (ANC) \< 1.0x10↑9/L or platelets \< 75x10↑9 /L * Signs or known history of bleeding disorder. * Significant hepatic dysfunction (total bilirubin ≥ 1.5x upper limit of normal (ULN) or transaminases ≥ 2.5 x ULN), unless related to Gilberts syndrome. * Clinical signs of severe cerebral dysfunction * Patients with a history of uncontrolled seizures, central nervous system disorders or psychiatric disability judged by the investigator to be clinically significant and adversely affecting compliance to study drugs * Major surgery within the last 4 weeks Known or suspected infection • Known active bacterial, viral, fungal, mycobacterial, parasitic, or other infection or any major episode of infection requiring treatment with IV antibiotics or hospitalization within 4 weeks of the start of Cycle 1. Suspected active or latent tuberculosis needs to be confirmed by positive interferon gamma (IFN-γ) release assay • Patients known to be Human Immuno-deficiency Virus (HIV)-positive * Active chronic hepatitis B or C infection * Administration of a live, attenuated vaccine within 4 weeks before date of registration or anticipation that such a live attenuated vaccine will be required during the study and for a period of 5 months after discontinuation of atezolizumab Auto-immune • Any active or history of documented autoimmune disease, including but not limited to myasthenia gravis, myositis, autoimmune hepatitis, systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease, vascular thrombosis associated with antiphospholipid syndrome, Wegener's granulomatosis, Sjögren's syndrome, Guillain-Barré syndrome, multiple sclerosis, vasculitis, or glomerulonephritis. The following exceptions are allowed: Patients with autoimmune-related hypothyroidism or type 1 diabetes mellitus who are on stable treatment. * History of idiopathic pulmonary fibrosis, organizing pneumonia (e.g., bronchiolitis obliterans), drug-induced pneumonitis, idiopathic pneumonitis, or evidence of active pneumonitis per chest computer tomography (CT) scan at screening. * Patients with uncontrolled asthma or allergy, requiring systemic steroid treatment * Regular treatment with corticosteroids within the 4 weeks prior to date of registration, unless administered for indications other than NHL at a dose equivalent to \< 30 mg/day prednisone/prednisolone General • Serious underlying medical conditions, which could impair the ability of the patient to participate in the trial (e.g. ongoing infection, uncontrolled diabetes mellitus, gastric ulcers, active autoimmune disease) • Current participation in another clinical trial interfering with this trial • History of active cancer during the past 5 years, except basal cell carcinoma of the skin, stage 0 cervical carcinoma or carcinoma in situ (for which no systemic treatment was indicated) • Life expectancy \< 6 months • Any psychological, familial, sociological and geographical condition potentially hampering compliance with the study protocol and follow-up schedule Prior treatment * Prior treatment with Atezolizumab, or anti-programmed cell death protein-1 (anti PD-1) or PDL-1 antibodies. * Prior treatment with CD137 agonists or immune checkpoint blockade therapies, including anti-CTLA4 therapeutic antibodies. * Treatment with systemic immunostimulatory agents (including but not limited to IFN, interleukin \[IL\]-2) within 6 weeks or 5 half-lives of the drug, whichever is shorter, prior to Cycle 1, Day 1. * Treatment with systemic immunosuppressive medications, including but not limited to prednisone, cyclophosphamide, azathioprine, methotrexate, thalidomide, and anti-tumor necrosis factor (anti-TNF) agents within 2 weeks prior to date of registration; inhaled corticosteroids and mineralocorticoids are allowed.