Erythropoietin in renal cell carcinoma: evaluation of its usefulness as a tumor marker.

Erythropoietin levels in serum were analyzed in 165 patients with renal cell carcinoma. All samples were taken before therapy and stored at -80 degrees C. Erythropoietin, a glucoprotein produced by the renal cortex was quantified by an enzyme immunoassay. Fifty-five of 165 patients (33%) had elevated serum levels. In patients with metastatic disease (M+), elevated levels were found in 24 of 65 cases (38%). Patients with high-grade tumors had significantly more often increased erythropoietin than those with low-grade tumors. No correlation between erythrocytosis and elevation of erythropoietin in serum was found. There was a significant difference in survival between patients with normal and patients with elevated erythropoietin levels (p = 0.013). The study shows that erythropoietin is a tumor marker with a low sensitivity. However, it correlates with stage and grade and provides prognostic information.