Study of a new drug for soft tissue cancer (rhabdomysarcoma) Disease/Condition: Adult Rhabdomyosarcoma | Alveolar Childhood Rhabdomyosarcoma | Embryonal Childhood Rhabdomyosarcoma | Metastatic Childhood Soft Tissue Sarcoma | Previously Untreated Childhood Rhabdomyosarcoma | Stage IV Adult Soft Tissue Sarcoma Principal Investigator: Nina Kadan-Lottick