Placental alkaline phosphatase as a tumor marker in ovarian cancer

The serum levels of placental alkaline phosphatase were determined with a radioimmunoassay using a polyclonal antibody on 1236 samples from 414 patients with ovarian cancer. The frequencies of elevated enzyme levels for patients with or without evidence of disease were 17.7 and 10.9%, respectively. The true positive rate was highest in serous cystadenocarcinoma, undifferentiated carcinoma, and dysgerminoma. A tendency to an inverse correlation with differentiation was found. Measurement of the enzyme did not give a useful index of stage of disease, tumor burden, or prognosis. The value of the enzyme as an index of successful therapy was limited because half of the patients lost this marker during progression. Further studies of the use of this enzyme as a tumor marker should evaluate the modulation of the placental alkaline phosphatase pattern during the course of the disease and should be based on monoclonal antibodies.