Targeted Immunotherapy After Myeloablative TBI-Based Conditioning & AlloHCT in CAYA With High Risk T-Cell ALL & Lymphoma

This study is testing a targeted immunotherapy approach after stem cell transplant in children, adolescents, and young adults with high-risk T-cell acute lymphoblastic leukemia (T-ALL) or T-cell lymphoblastic lymphoma that has come back or is not responding to treatment. **You may be eligible if...** - You are between 0 and 39 years old - You have T-cell ALL in second or later remission (less than 5% cancer cells remaining), or T-cell lymphoblastic lymphoma that has achieved a complete response after re-induction treatment - You have a matched donor identified for an allogeneic stem cell transplant - You have recovered from prior chemotherapy side effects - Your organ function meets the minimum requirements **You may NOT be eligible if...** - You have had a prior stem cell transplant (autologous or allogeneic) - You have an active, uncontrolled infection - You have known allergies to key study medications (such as mannitol, corticosteroids, or monoclonal antibodies) Talk to your doctor to see if this trial is right for you.