POLA+BR for Relapsed or Refractory DLBCL

The first day of treatment will constitute Cycle 1 Day 1. Patients will be treated with a minimum of three cycles and up to a maximum of 6 cycles to optimize responses prior to ASCT based on investigator discretion. All patients will be evaluated for safety and efficacy according to the schedules of assessments. All patients will be assessed for response to treatment by the investigator with the use of standard criteria according to the Modified Lugano Response Criteria at the following time points: * At the time of screening * At the time of primary response assessment (3 weeks after completion of study treatment (i.e., 3 weeks after Cycle 3 Day 1 or after last dose of study medication) Imaging at these timepoints must include FDG-PET (18F-fluorodeoxyglucose-positron emission tomography) and a diagnostic-quality CT scan with both oral and IV contrast. A combined PET/CT scan is encouraged if feasible. CT scans with oral and IV contrast should include neck, chest, abdomen, and pelvic scans. In patients for whom contrast is contraindicated, (e.g., patients with contrast allergy or impaired renal clearance or patient denial), PET-CT scans without contrast are permitted so long as they permit consistent and precise measurement of target lesions during the study treatment period. Patients will also be evaluated every 3 months for 2 years, or until disease progression, death, withdrawal of consent, or initiation of another anti-cancer therapy. Tumor assessments should also be performed to confirm clinical suspicion of relapse or disease progression for documentation. The study will end when all patients enrolled have been followed until death, have withdrawn consent, have been lost to follow-up, until 2-year follow up, or the Sponsor-investigator decides to end the trial, whichever occurs first.