Cognitive Aftereffects of Neurotoxicity in Children and Young Adults With Relapsed/Refractory Hematologic Malignancies Who Receive CAR T-cell Therapy

Background: * Chimeric antigen receptor (CAR) T-cell immunotherapy has rapidly emerged as a successful and breakthrough treatment in pediatric and adult hematologic malignancies. However, significant toxicities can complicate the therapeutic successes of such therapy, including neurologic toxicity associated with cytokine release syndrome (CRS). * There is a critical need to characterize the subacute and long-term neurocognitive outcomes of participants undergoing CAR T-cell therapies and to compare the results across trials, some of which are first-in-human studies. It is unknown how acute toxicity affects attention, learning, memory, processing speed, and higher order cognition in participants who are cured of their cancer and survive for many years. Information about subacute and long-term neurocognitive sequelae would help determine whether the acute toxicity of specific CAR T-cell therapies needs to be treated and prevented aggressively or whether it is fully reversible without specific intervention. Objective: -To evaluate changes in working memory in children and young adults with relapsed/refractory leukemia or lymphoma at 12 months post CAR T-cell therapy Eligibility: * Children and young adults (age \>= 5 and \<=35 years old) with relapsed/refractory leukemias or lymphomas scheduled to have CAR T-cell therapy and their caregivers (informants). * Participants who can speak and read in English or Spanish Design: * This is a multi-center pilot trial to study the neurocognitive effects of CAR T-cell therapy. * Eligible participants will be seen in one of the enrolling sites. * Neurocognitive evaluations will be conducted using a computerized test battery (Cogstate) and other paper/pencil tests that assess cognitive processes known to be most affected in participants treated for leukemia or lymphomas as well as patient-reported and observer-reported outcome measures. Participants with the disease and their informants will be enrolled in this study during the preparation of participants for CAR T-cell therapy and followed for up to 3 years post CAR infusion.