Breakthrough cancer pain in the radiotherapy setting: a systematic and critical review.

Qualitative and quantitative data regarding BP in the RT setting are poor in terms of scientific evidence. Most papers assessed fentanyl products, particularly fentanyl pectin nasal spray, to resolve possible problems with transmucosal absorption of fentanyl due to mucositis of the oral cavity in patients with head and neck cancer or to prevent and treat procedural pain during RT sessions. According to the lack of clinical studies with large number of patients, BP should be included in the agenda of radiation oncologists.