Chapter 01 - Safeguarding Exercise Capacity Throughout and After Cancer Treatment
Reduced Muscle Mass and Strength
Muscle wasting is present in approximately 50% of cancer survivors, contributing to decreased responsiveness to cancer treatment and severe dose-limiting toxicities, in turn contributing to poor prognosis and increased morbidity and mortality. Because muscle strength is related to muscle mass, muscle wasting also contributes to weakness and reduced functional ability and independence. In addition, due to its mediating role, muscle wasting may have serious consequences on glucose metabolism and chronic low-level systemic inflammation. Muscle wasting results from an imbalance between the rate of muscle protein synthesis and degradation and, in particular, from accelerated muscle protein degradation. Mechanisms underlying muscle protein degradation include tumour- and treatment-related increases in pro-inflammatory cytokines and proteolysis-inducing factors, as well as testosterone suppression, reduced food intake, and low physical activity levels.
Increased Fat Mass
Cancer and its treatment are commonly associated with changes in body composition. The specific detrimental changes in total weight, lean body mass, and fat mass differ by cancer and treatment types. An increase in fat mass is common during adjuvant treatments, for example for breast, colon, prostate, and gynaecological cancer, which has a significant impact on the risk of type 2 diabetes, asthma, chronic back pain, osteoarthritis, metabolic syndrome, and cardiovascular disease. In addition, obesity has been associated with a poorer overall and cancer-specific survival.