A clinical evaluation of serum placental alkaline phosphatase in seminoma patients.

Serum levels of placental alkaline phosphatase (PLAP) were measured in 100 patients with seminoma. A specific double antibody radioimmunoassay was used. PLAP was elevated for 9 out of 21 patients with primary tumours, to a mean of 53 micrograms/l. Of the 12 cases with recurrent or metastatic growth, nine had raised PLAP. The sensitivity of PLAP determinations for primary and advanced disease was 55%. After successful treatment of seminoma, the PLAP level decreased. In a group of 68 patients with no evidence of disease, nine had slightly elevated serum PLAP. In many, but not all patients, serum PLAP parallelled the changes in tumour burden. In such patients and for follow-up of treatment, PLAP might be used as a new marker for seminomatous disease.