Prevalence of paraneoplastic erythropoietin production by renal cell carcinomas.

The prevalence of increased serum immunoreactive erythropoietin (Epo) was determined in a prospective study of 49 patients with renal cell carcinoma. Measured by a monoclonal antibody based commercial enzyme-linked immunoassay, the Epo concentration was above the normal range, determined in nonanemic humans, in four of the renal carcinoma patients. Since three of these were anemic, their increased Epo level was considered to be appropriate. The high estimate of serum Epo (218 U/l) in the fourth patient, who was not anemic, was not confirmed when tested by radioimmunoassay. Thus, in contrast with earlier studies, our results indicate that increased Epo is not a clear serological renal cell carcinoma marker. In addition, when monolayer cell cultures of 14 different established human renal carcinoma lines were screened, none of these released immunoreactive Epo in measurable amounts.