Determination of plasma erythropoietin levels: an early marker of tumor activity.

A young female patient developed erythrocytosis during the third recurrence of a cerebellar hemangioblastoma. Elevated erythropoietin levels were found in the patient's plasma with normalization after resection of the tumor. High erythropoietin titers were also found in the tumor saline extract. A fourth recurrence of the tumor was heralded by a rising plasma erythropoietin level and gradual erythrocytosis despite the absence of change in the clinical picture or the brain scan. In this case, serial plasma erythropoietin determinations served as a useful early marker of the tumor activity.