CNS-BRT response. (A) Paired lesion-size analysis shows a significant decrease in lesion size after CNS-BRT, before CAR T-cell infusion (P = .014). The mean decrease in lesion size was 74.8%. (B) Baseline imaging and CNS-BRT response for patients with leptomeningeal lesions. Patient 1: coronal T1 postcontrast MRI through orbits shows disease centered in bilateral superolateral extraconal fat (asterisks) and infiltrating the bilateral infraorbital nerves (arrowheads); 55 days after radiotherapy (RT) completion there is near complete resolution of orbital masses and decreased prominence of the infraorbital nerves. Patient 3: sagittal T1 postcontrast MRI of the lumbar spine demonstrating enhancing soft tissue mass filling much of the thecal sac from T12-L2; 19 days after RT completion there is marked decrease in intrathecal contrast enhancement (arrowheads). Patient 10: sagittal T1 postcontrast MRI of the lumbar spine showing enhancing soft tissue mass filling much of the thecal sac from T12 to superior extent of L2; 43 days after RT completion there is near complete resolution of the mass (arrowheads). Patient 3 and 10 had bulky spinal leptomeningeal lesions. (C) Baseline imaging and CNS-BRT response for patients with parenchymal brain lesions. All images show axial T1 postcontrast MRIs of the brain. Patient 5: enhancing lesion centered in the right occipital lobe shows significant reduction in size 2 days after RT completion. Patient 6: enhancing right frontal/operculum lesion shows significant reduction in size, 3 days after RT completion. Patient 9: enhancing paramedian lesion at the right frontoparietal convexity shows marked reduction in size, 42 days after RT completion. Patient 11: enhancing lesion centered in the left thalamus shows significant contraction, 4 days after RT completion. Patient 12: enhancing right gangliocapsular lesion shows near complete resolution, 5 days after RT completion.