An Observation Study to Assess the Efficacy and Safety of Proportional Doses of Painkyl® in Patients With Breakthrough Cancer Pain

Inclusion Criteria: 1. cancer patients regularly experienced 1 to 3 breakthrough pain episodes per day that required additional opioids from pain control; 2. a current regimen of opioids equivalent to 60-360 mg/day of oral morphine or 25-150 mcg/hr of transdermal fentanyl for one week or longer; 3. at least partial relief of breakthrough pain by use of opioid therapy; 4. able to self-administer the study medication correctly or has an available adult caregiver to administer the study medication correctly; 5. willing and able to complete patient diary with each pain episode. 6. 20 to 80 years of age; Exclusion Criteria: 1. rapidly escalating pain (e.g., regularly more than 3 breakthrough pain episodes per day) that are hard to be controlled by analgesics; 2. history of hypersensitivity or intolerance to fentanyl; 3. cardiopulmonary disease that, in the opinion of the investigator, would significantly increase the risk of respiratory depression; 4. psychiatric/cognitive or neurological impairment that would limit the subject's ability to understand or complete the diary; 5. Severe (Grade 4) mucositis (subjects with less than severe mucositis are permitted and must be instructed to not apply the Painkyl® film at a site of inflammation); 6. abnormal oral mucosa which will impede drug absorption; 7. recent history or current evidence of alcohol or other drug substance (licit or illicit) abuse; 8. use of an investigational drug or other rapid-onset opioids drugs within 4 weeks preceding this study; 9. pregnant women or nursing mothers, or positive pregnancy test for women of childbearing potential.