Subsequent to durvalumab infusion, rituximab was administered by IV. Rituximab administration could be split over 2 consecutive days according to local clinical practice. Rapid infusion of rituximab was not allowed in this clinical study.

A component of the CHOP therapy administered by IV. CHOP therapy was administered following rituximab.

A component of the CHOP therapy administered by IV. CHOP therapy was administered following rituximab.

A component of the CHOP therapy administered by IV. CHOP therapy was administered following rituximab.

Prednisone was administered as an IV infusion or by mouth (PO) on Day 1, followed by PO administration on Days 2-5 of each cycle.

Prednisone could be given prior to other drugs of the CHOP therapy. It was administered after lenalidomide dosing in the R2-CHOP treatment arm.

Lenalidomide was administered orally in capsule form on Days 1-14 of the DUR+R2-CHOP treatment arm only.

Data in the analysis include all participants who received durvalumab, irrespective of the study arm in which they enrolled, because the selected biomarkers have been associated with response in other anti-PD1 or anti-PDL1 studies, such as durvalumab. IHC analysis was performed on the baseline tumor biopsy to quantify CD8 T-cell density. Participants with 'high' values, i.e. above the threshold defined as the median value of 774 cells/mm^2 found in commercial DLBCL samples using matched analytical methods, were predicted to be responders to treatment with durvalumab. The definition of a complete response was that used in the primary outcome.

Data in the analysis include all participants who received durvalumab, irrespective of the study arm in which they enrolled, because the selected biomarkers have been associated with response in other anti-PD1 or anti-PDL1 studies, such as durvalumab. IHC analysis was performed on the baseline tumor biopsy to quantify CD8 T-cell density. Participants with 'high' values, i.e. above the threshold defined as the median value of 774 cells/mm^2 found in commercial DLBCL samples using matched analytical methods, were predicted to be responders to treatment with durvalumab. The definition of a complete response was that used in the primary outcome.

Data in the analysis include all participants who received durvalumab, irrespective of the study arm in which they enrolled, because the selected biomarkers have been associated with response in other anti-PD1 or anti-PDL1 studies, such as durvalumab. IHC analysis was performed on the baseline tumor biopsy to quantify CD8 T-cell density. Participants with 'high' values, i.e. above the threshold defined as the median value of 774 cells/mm^2 found in commercial DLBCL samples using matched analytical methods, were predicted to be responders to treatment with durvalumab. The definition of a complete response was that used in the primary outcome.

Data in the analysis include all participants who received durvalumab, irrespective of the study arm in which they enrolled, because the selected biomarkers have been associated with response in other anti-PD1 or anti-PDL1 studies, such as durvalumab. IHC analysis was performed on the baseline tumor biopsy to quantify CD8 T-cell density. Participants with 'high' values, i.e. above the threshold defined as the median value of 774 cells/mm^2 found in commercial DLBCL samples using matched analytical methods, were predicted to be responders to treatment with durvalumab. The definition of a complete response was that used in the primary outcome.

An AE is any noxious, unintended, or untoward medical occurrence that may appear or worsen during a study. A serious AE is any AE occurring at any dose that: • Results in death; • Is life-threatening; • Requires or prolongs existing inpatient hospitalization; • Results in persistent or significant disability/incapacity; • Is a congenital anomaly/birth defect; • Constitutes an important medical event. The Investigator assessed the relationship of each AE to study drug and graded the severity according to the National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE, Version 4.03): - Grade 1 = Mild (no limitation in activity or intervention); - Grade 2 = Moderate (some limitation in activity; no/minimal medical intervention required); - Grade 3 = Severe (marked limitation in activity; medical intervention required, hospitalization possible); - Grade 4 = Life-threatening; - Grade 5 = Death. Relation to IP is determined by the investigator.

Participants receive Induction Therapy (21-day cycles): Cycle 1 - induction therapy of durvalumab in combination with R-CHOP (as described in DUR + R-CHOP arm). Starting at cycle 2 - Durvalumab 1125 mg IV on Day 1 of each 21-day cycle in combination with 6 to 8 cycles R2-CHOP (IV rituximab, doxorubicin, vincristine and cyclophosphamide on Day 1; daily oral/IV prednisone/prednisolone from Day 1 to 5; daily oral lenalidomide 15 mg from Day 1 to 14) from the cycle following COO determination until end of induction therapy (Cycle 6 or Cycle 8) or starting Cycle 1 if ABC subtype is identified prior to C1D1.

Participants then receive Consolidation Therapy (28-day cycles): Durvalumab 1500 mg IV on Day 1 of each 28-day cycle for up to a total of 12 months from C1D1 of induction therapy.

Participants receive Induction Therapy (21-day cycles): Cycle 1 - induction therapy of durvalumab in combination with R-CHOP (as described in DUR + R-CHOP arm). Starting at cycle 2 - Durvalumab 1125 mg IV on Day 1 of each 21-day cycle in combination with 6 to 8 cycles R2-CHOP (IV rituximab, doxorubicin, vincristine and cyclophosphamide on Day 1; daily oral/IV prednisone/prednisolone from Day 1 to 5; daily oral lenalidomide 15 mg from Day 1 to 14) from the cycle following COO determination until end of induction therapy (Cycle 6 or Cycle 8) or starting Cycle 1 if ABC subtype is identified prior to C1D1.

Participants then receive Consolidation Therapy (28-day cycles): Durvalumab 1500 mg IV on Day 1 of each 28-day cycle for up to a total of 12 months from C1D1 of induction therapy.

Participants had IHC analysis performed on a biopsy sample collected before treatment on this protocol. The result of their CD8 density evaluation was below threshold,defined as the median of 774 cells/mm^2 found in commercial DLBCL samples using matched analytical methods. Participants with values below threshold were predicted to be non-responders.

Participants had IHC analysis performed on a biopsy sample collected before treatment on this protocol. The result of their PDL1 % of total cell evaluation was below threshold,defined as the median of 13.8% found in commercial DLBCL samples using matched analytical methods. Participants with values below threshold were predicted to be non-responders.

Participants had IHC analysis performed on a biopsy sample collected before treatment on this protocol. The result of their PDL1 % of tumor cell evaluation was below threshold,defined as the median of 6.2% found in commercial DLBCL samples using matched analytical methods. Participants with values below threshold were predicted to be non-responders.

Participants had RNA IFN Gamma Score calculated based on a biopsy sample collected before treatment on this protocol. The result of their RNA IFN Gamma Score was below threshold,defined as the median of 3.28 found in commercial DLBCL samples using matched analytical methods. Participants with values below threshold were predicted to be non-responders.

Participants receive Induction Therapy (21-day cycles): Cycle 1 - induction therapy of durvalumab in combination with R-CHOP (as described in DUR + R-CHOP arm). Starting at cycle 2 - Durvalumab 1125 mg IV on Day 1 of each 21-day cycle in combination with 6 to 8 cycles R2-CHOP (IV rituximab, doxorubicin, vincristine and cyclophosphamide on Day 1; daily oral/IV prednisone/prednisolone from Day 1 to 5; daily oral lenalidomide 15 mg from Day 1 to 14) from the cycle following COO determination until end of induction therapy (Cycle 6 or Cycle 8) or starting Cycle 1 if ABC subtype is identified prior to C1D1.

Participants then receive Consolidation Therapy (28-day cycles): Durvalumab 1500 mg IV on Day 1 of each 28-day cycle for up to a total of 12 months from C1D1 of induction therapy.