Radiation, Oral Vancomycin, and CAR-T for B-Cell Lymphomas

Inclusion Criteria: * Male or female subject aged ≥ 18 years. * Pathologically confirmed B-cell lymphoma patients intended for standard of care CAR-T * ECOG Performance Status ≤ 2. * Subjects must be clinically eligible to receive standard of care anti-CD19 CAR-T * Subjects must have at least one site of disease amenable to radiation, with the ability to deliver radiation to at least 50% of involved sites * Subjects must have at least one site of measurable disease based on CT or FDG PET * Subjects must not be anticipated to require additional therapy beyond bridging radiation listed in this protocol for control of their lymphoma * For female subjects: Negative pregnancy test or evidence of post-menopausal status. The post-menopausal status will be defined as having been amenorrheic for 12 months without an alternative medical cause. The following age-specific requirements apply: Women \< 50 years of age: amenorrheic for ≥ 12 months following cessation of exogenous hormonal treatments; and luteinizing hormone and follicle-stimulating hormone levels in the post-menopausal range for the institution; or Underwent surgical sterilization (bilateral oophorectomy or hysterectomy). Women ≥ 50 years of age: amenorrheic for 12 months or more following cessation of all exogenous hormonal treatments; or had radiation-induced menopause with last menses \>1 year ago; or had chemotherapy-induced menopause with last menses \>1 year ago; or underwent surgical sterilization (bilateral oophorectomy, bilateral salpingectomy, or hysterectomy). * Able to provide informed consent and willing to sign an approved consent form that conforms to federal and institutional guidelines. * Stated willingness to comply with all study procedures and availability for the duration of the study Exclusion Criteria: * Unable to take oral vancomycin for any reason, including: Allergy or Inability to swallow drug * Known history of vancomycin resistant enterococcus (VRE) * Contraindications to radiation therapy, including scleroderma, systemic lupus erythematosus, Crohn disease, ulcerative colitis, or idiopathic pulmonary fibrosis * History of radiation pneumonitis or other grade 4 radiation-related adverse event * Prior or concurrent malignancy whose natural history or treatment which has the potential to interfere with the safety or efficacy assessment of the radiation therapy are eligible for this trial. * Severe, uncontrolled, significant intercurrent or recent illness that would exclude them from being a candidate for standard-of-care CART therapy. * Known uncontrolled HIV infection with a detectable viral load at the time of screening. Note: Patients on effective antiretroviral therapy or who will plan on going on antiretroviral therapy at the time of screening are eligible for this trial. HIV testing is not required for eligibility. * Active infection that required the use of antibiotics within 4 weeks prior to registration * Any other condition that would, in the investigator's judgment, contraindicate the subject's participation in the clinical study due to safety concerns or compliance with clinical study procedures