Until now, cancer is still associated with high morbidity and mortality, and is therefore a big issue for the public health. Colorectal cancer is the second leading cause of cancer death in developed countries. In advanced colorectal cancer, 60% of these patients develop cachexia. The presence of cachexia plays an important role in the high mortality rate of cancer. Cachexia is characterized by involuntary weight loss with loss of skeletal muscle with or without loss of fat mass. The aim of this study is to determine the feasibility of taking muscle biopsies of cachectic colorectal cancer patients. Skeletal muscle characteristics will be compared between biopsies of the m. erector spinae and the m. vastus lateralis from cachectic colorectal cancer patients, non-cachectic colorectal cancer patients and healthy controls. 10 cachectic, 25 non-cachectic, and 25 healthy controls will be recruited for this study. It is an observational study, so measurements will be taken at one time point. Interventions/measurements: * muscle biopsies * blood samples * 3D freehand ultrasound * Short physical performance battery test * handgrip strength * questionnaires (activity pattern, quality of life)