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

Breakthrough pain (BP) is a complex phenomenon that has been reported to have a relevant role in the global management of cancer pain. Radiotherapy (RT) has a fundamental part in the treatment of many pain conditions, particularly oral mucositis and painful bone metastases. The literature regarding the phenomenon of BP in the radiotherapy setting was reviewed. Three areas were assessed, including epidemiology, pharmacokinetics, and clinical data. 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.