title: Muscle dysfunction in cancer patients.
abstract: BACKGROUND
  Muscle dysfunction is a prevalent phenomenon in the oncology setting where patients across a wide range of diagnoses are subject to impaired muscle function regardless of tumor stage and nutritional state. Here, we review the current evidence describing the degree, causes and clinical implications of muscle dysfunction in cancer patients. The efficacy of exercise training to prevent and/or mitigate cancer-related muscle dysfunction is also discussed.
  
  
  METHODS
  We identified 194 studies examining muscular outcomes in cancer patients by searching PubMed and EMBASE databases.
  
  
  RESULTS
  Muscle dysfunction is evident across all stages of the cancer trajectory. The causes of cancer-related muscle dysfunction are complex, but may involve a wide range of tumor-, therapy- and/or lifestyle-related factors, depending on the clinical setting of the individual patient. The main importance of muscle dysfunction in cancer patients lies in the correlation to vital clinical end points such as cancer-specific and all-cause mortality, therapy complications and quality of life (QoL). Such associations strongly emphasize the need for effective therapeutic countermeasures to be developed and implemented in oncology practice. Significant progress has been made over the last decade in the field of exercise oncology, indicating that exercise training constitutes a potent modulator of skeletal muscle function in patients with cancer.
  
  
  CONCLUSIONS
  There are clear associations between muscle dysfunction and critical clinical end points. Yet there is a discrepancy between timing of exercise intervention trials, which can improve muscle function, and study populations in whom muscle function are proven prognostic important for clinical end points. Thus, future exercise trials should in early-stage patients, be powered to evaluate clinical outcomes associated with improvements in muscle function, or be promoted in advanced stage settings, aiming to reverse cancer-related muscle dysfunction, and thus potentially improve time-to-progression, treatment toxicity and survival.
authors.affiliation: The University Hospitals Centre for Health Care Research (UCSF).
authors.forename: J F
authors.initials: JF
authors.lastname: Christensen
authors.forename: L W
authors.initials: LW
authors.lastname: Jones
authors.forename: J L
authors.initials: JL
authors.lastname: Andersen
authors.forename: G
authors.initials: G
authors.lastname: Daugaard
authors.forename: M
authors.initials: M
authors.lastname: Rorth
authors.forename: P
authors.initials: P
authors.lastname: Hojman
mesh_terms: D000818:Animals; D005081:Exercise Therapy; D006801:Humans; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000473:pathology / Q000503:physiopathology*; D009369:Neoplasms / Q000401:mortality / Q000503:physiopathology* / Q000628:therapy; D011788:Quality of Life; D016896:Treatment Outcome
keywords: cancer; exercise; muscle mass; muscle strength; skeletal muscle