PEctin Rapid Fentanyl Efficacy Clinical Trial For pAin at Swallowing Undergoing radioTherapy

Inclusion criteria: 1. Male and female aged 18 years or over 2. Diagnosis of stage III-IV cancer of oral cavity, oropharynx, hypopharynx, larynx, salivary glands 3. Receiving radiation therapy (RT) with or without concurrent platinum based chemotherapy or cetuximab as first line treatment or as postoperative adjuvant treatment 4. Background pain controlled with at least 60 mg oral morphine daily or an equianalgesic dose of another opioid. A "background pain controlled" is defined as NRS \<4 5. Uncontrolled pain during swallowing (predictable BTP at swallowing) with an intensity ≥4 on an 11-point numeric scale (0=no pain; 10=worst possible pain). This pain will have to be measured with the ingestion of a solid/liquid food (depending on the ability to swallow or less solid foods of the patient at moment) 6. Patients able to receive a nasal spray therapy 7. Willing and able to sign an informed consent form 8. Females with childbearing potential must provide a negative pregnancy test and both males and females must be using adequate contraception during the study 9. Patients with PEG or jejunostomy, if are available to take by mouth meals (solid or liquid) or just liquid in order to be compliant with the protocol. Exclusion Criteria: 1. Patients with known metastatic disease 2. Known hypersensitivity to opioids, to Fentanyl or to drugs used in the PC-UC, and/or to study medications' formulation ingredients 3. Patients with impaired chemistry laboratory exams, assessed as routine clinical practice before radiotherapy start: a. Hepatic function: i. Total bilirubin \> 2 times the upper-normal limit (ULN) ii. Serum transaminase \> 5 times ULN b. Renal function: i. Serum creatinine concentration \> 2 times ULN 4. Pregnant or breastfeeding women 5. Patients unlikely to comply with the protocol or unable to understand the nature, scope and possible consequences of the study 6. Patients planned to receive other investigational treatments during study period 7. Patients with moderate to severe respiratory impairment 8. Patients with nasogastric feeding tube 9. Patients that cannot take FPNS according to investigator's judgment