The Etiology and management of radiotherapy-induced fatigue.

Fatigue is one of the most common side-effects accompanying radiotherapy, but arguably the least understood. Radiotherapy-induced fatigue (RIF) is a clinical subtype of cancer treatment-related fatigue. It is described as a pervasive, subjective sense of tiredness persisting over time, interferes with activities of daily living, and is not relieved by adequate rest or sleep. RIF is one of the early side-effects and long-lasting for cancer patients treated with localized radiation. Although the underlying mechanisms of fatigue have been studied in several disease conditions, the etiology, mechanisms, and risk factors of RIF remain elusive, and this symptom remains poorly managed. The purpose of this paper is to review and discuss recent articles that defined, proposed biologic underpinnings and mechanisms to explain the pathobiology of RIF, as well as articles that proposed interventions to manage RIF. Understanding the mechanisms of RIF can describe promising pathways to identify at-risk individuals and identify potential therapeutic targets to alleviate and prevent RIF using a multimodal, multidisciplinary approach.