All subjects start treatment with a 12.5 micrograms/hour patch. Immediate-release morphine is available to treat breakthrough pain. The patches are replaced every 72 hours. The objective is to have subjects pain-free as much as possible, using the least possible rescue medication. Duragesic® dose increases are considered based on rescue medication consumption and pain assessment. Where a subject is maintained pain-free with a daily consumption of 45 mg of rescue morphine or more, a dose increase of Duragesic® with 12.5 micrograms/hour is permitted. No increase in Duragesic® dose is to be performed within the 72-hour dosing interval. The primary outcome of this study is an assessment of safety, including the incidence and severity of adverse events, and physical examination results and vital signs. Clinical utility is assessed by the parent's treatment assessment of pain relief, tolerability and convenience (pre-treatment and after each patch change); the investigator's and the parent's global assessments on Day 16 of pain control, adverse events, and convenience; daily measures of pain levels; use of rescue medication; and the child's play performance. Pharmacokinetics will also be assessed. Duragesic® will be applied to the upper torso, and replaced every 72 hours. The initial dose is one patch with a fentanyl delivery rate of approximately 12.5 micrograms/hour. Dose increases in steps of 12.5 micrograms/hour are considered if pain is inadequately controlled. The treatment phase is 15 days.