My get up and go got up and went: fatigue in people with cancer.

Many gaps remain in understanding fatigue across the phases of the cancer experience. These include determining the extent to which fatigue is a presenting or continuing symptom of cancer or a side effect of cancer treatment, identifying those at highest risk of fatigue, defining factors that differentiate between those who do and do not experience fatigue, and characterizing fatigue in special populations such as those with advanced cancer, children, and elders. This article reviews current knowledge of who experiences fatigue, the relationship of fatigue to cancer treatment, and the phenomenon of persistent fatigue following treatment. Critical elements in the research agenda that need to be addressed include the relationship of fatigue to other symptoms of cancer or side effects of treatment, mechanisms underlying fatigue and the development of mechanism-specific approaches to preventing and managing this troublesome symptom.