Fig. 4

Muscle wasting, serum CK decrease, and sex. In cancer patients, skeletal muscle wasting leads to a decrease in SMA, with a more pronounced reduction in type II muscle fibers compared to type I muscle fibers. Additionally, the synthesis of CK-MM in muscle fibers is inhibited in the inflammatory environment caused by cancer, which further contributes to the reduction of CK-MM efflux from muscle fibers into the bloodstream. Estrogen may be a factor contributing to the lack of prognostic significance of CK in females. CK, creatine kinase; SMA, skeletal muscle area