CGA and neoplasm: Whereas the European Neuroendocrine Tumor Society (refs. 11, 19) and European Society for Medical Oncology (ref. 9) guidelines support serial measurements of circulating CgA for the management of patients with GEP-NET, the National Comprehensive Cancer Network (ref. 10) and North American Neuroendocrine Society (ref. 8) guidelines do not contain a clinical algorithm for CgA.