Single-Arm Comprehensive Ablative Bridging Irradiation I Prior to CD19 CAR-T In High-Risk R/R LBCL

Inclusion Criteria: * Patients with a histologically confirmed diagnosis of diffuse large B-cell lymphoma (DLBCL) who plan to receive treatment at the Moffitt Cancer Center will be eligible. * Must have ability to comprehend and the willingness to sign written informed consent for study participation. * Eligible to receive CAR T-cell therapy (axicabtagene ciloleucel) for LBCL and histological variants approved by the standard of care label * ECOG performance status 0 to 2. * At least one high-risk lesion, defined as measuring ≥ 5 cm, that is targetable for radiotherapy per investigator assessment. * Ability to undergo comprehensive bridging radiation, defined as radiation to all visible sites of disease. * No evidence or suspicion of active central nervous system (CNS) involvement of lymphoma * Adequate bone marrow and organ function as defined in protocol. The effects of therapeutic agents used in this trial on developing human fetus are unknown, and because of this, women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation as outlined in criteria below: * Men must agree to take appropriate precautions to avoid fathering children (with at least 99% certainty) from screening through safety follow up and must refrain from donating sperm during this period. Permitted methods that are at least 99% effective in preventing pregnancy …