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.
We identified 194 studies examining muscular outcomes in cancer patients by searching
PubMed and EMBASE databases.
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.
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.