Sarcopenia associated with chemotherapy and targeted agents for cancer therapy
Clinicians often believe that cachexia is caused by cancer and anorexia as a toxicity of chemotherapy or targeted anti-cancer agents. It is now recognized that chemotherapy and certain targeted agents cause sarcopenia which reduce physical function and quality of life. Pre-treatment sarcopenia predicts chemotherapy toxicity, reduced response, increased disability, poor anti-tumor response and survival. Though bioelectrical impedance and dual energy X-ray absorptiometry (DEXA) scans have been used in the past for body composition measurements, CT scan cuts at the level of the 3rd lumbar vertebral body with measurement of skeletal muscle and visceral and subcutaneous fat areas has become standard. Nonpharmacological approaches to reducing sarcopenia during chemotherapy includes resistance training and dietary counselling. Pharmacologic therapies include vitamin D replacement if depleted, omega-3 fatty acids, testosterone and selective androgen receptor modulators (SARMS) and ghrelin. A comprehensive multimodal and multiple drug approach is likely to be better than single modalities. However, this is yet to be proven. Finally, it is not known if intervening to prevent or reverse sarcopenia will have a clinical benefit in terms of better tolerance to cancer therapy, physical function, well-being, tumor response and survival. Reversing sarcopenia and improving objective outcomes should be the goal of therapy.