The value of erythropoietin assay in the follow-up of Wilms' tumor patients.

Ectopic tumor associated erythropoietin release was measured preoperatively and postoperatively in 36 Wilms' tumor patients followed for an average of three years. Erythropoietin assay results in plasma and urine were related independently to tumor stage as well as to the general clinical judgment following appropriate and exhaustive tests as to whether the disease was active or inactive at the time of the assay. Consistent erythropoietin plasma elevations were correlated with the presence of active disease in all stages of Wilms' tumor. Less consistent elevations were noted in urine specimens concomitantly obtained and assayed. This hormonal assay continues to be of consistent and long-term benefit in predicting or correlating disease recurrence or persistence in Wilms' tumor.