Burketts relapse after bone marrow transplant

Hi. I have a nephew, Mason, who has been battling Burketts Lymphoma for about a year. He is 10 years old. Orignally, he had a tumor in his abdomen when he was diagnosed. It was surgically removed and he started chemo. He went into remission a few months later, but then relapsed. Cancer cells were detected in his Central nervous system, but he had no tumors.  More chemo, which sent him into remission, and he then received bone marrow from his younger brother. He has received marrow I think twice from his brother. He has relapsed again, His Omaaya (sp?) tap showed 300 white cells. The doctors think that the disease has mutated and become "invisible" to his own immune system. They started more chemo, and his numbers went down to 33, then to 5. So the Burketts is still responding to chemo, but this may only buy him a little time until the doctors figure out what to do next. The family is asking for help in finding a doctor who has successfully treated Burketts in patients who have relapsed after Bone Marrow Transplant. He lives in the Atlanta area, and I believe he is being treated at St. Jude hospital. Does anyone know or have a docotr that has sucessfully treated Burketts in patients after a bonew marrow transplants? Any suggestions would be greatly appreciated.
MM