Adaptive Bridging RT in R/R B-cell Lymphoma (Pre-CAR T)

Inclusion Criteria: * Diagnosis of relapsed or refractory B-cell lymphoma (including, but not limited to diffuse large B-cell lymphoma (DLBCL) not otherwise specified, primary mediastinal large B-cell lymphoma, high grade B-cell lymphoma, DLBCL arising from follicular lymphoma, follicular, and mantle cell lymphoma) * Being planned to undergo CAR T-cell therapy (patients can be enrolled prior to apheresis) * At least 1 measurable lesion according to the Lugano criteria35. Lesions that have been previously irradiated will be considered measurable only if progression has been documented following completion of radiation therapy. Re-irradiation is allowed for these patients. More than 1 lesion can be targeted as per radiation oncologist discretion. If disease is palpable, physical examination alone may be sufficient measurement for disease if a recent PET/CT or CT is not available as a radiologic measurement of the disease can be obtained during CT simulation. * Age ≥ 18 years * Eastern Cooperative Oncology Group (ECOG) performance status of less than or equal to 3. * Ability to understand and the willingness to sign a written informed consent document Exclusion Criteria: * Any medical condition likely to interfere with assessment of safety or efficacy of RT. * CNS-only disease as the site for bridging radiation therapy (which cannot be reliably evaluated on CT). Patients with CNS disease with extra-axial involvement that can be evaluated on CT remain eligible. * Patient likel…