EPO and cancer: ESAs are still the most commonly used drugs for the clinical treatment of renal anemia but the simple administration of ESAs often does not achieve satisfactory results, and about 5% to 10% of patients respond poorly to ESAs.[2] Research has found that the main reasons for the poor efficacy of ESAs include the presence of iron deficiency, inflammation, erythropoietin (EPO) inhibitors, malignant tumors, and secondary hyperparathyroidism.[3,4]