Every type of cancer causes muscle loss. The main reason all cancer types cause muscle loss is because the body is producing cytokines to fight the cancer, as stated by cancercare.org.
Another reason all types of cancers cause muscle loss is because of the treatments patients have to go through. In most cases, chemotherapy and radiation causes patients to have a decrease in appetite or sores in their mouth, which indirectly leads to the muscle loss through a decrease in exercise and eating. The cancer itself and the treatments can lead to fatigue that causes patients to lose their ability to perform the physical activities they had performed previously.