1. Specific eligible disease: Patients must have been diagnosed and be in treatment for a childhood cancer or a similar disease. Examples of cancers that will be included in the trial are: Acute Lymphoblastic Leukemia, Acute Myelogenous Leukemia, lymphoma, rhabdomyosarcoma, osteosarcoma, Hodgkins and Non-Hodgkins Lymphoma, and Pediatric Brain Tumor (malignant and non-malignant are included since they receive the same treatments).