Multicenter evaluation of human placental alkaline phosphatase as a possible tumor-associated antigen in serum

Using a solid-phase monoclonal antibody enzyme immuno-assay, we evaluated in a multicenter study (18 laboratories) the utility of evaluating catalytic activity of human placental alkaline phosphatase (hPLAP, EC 3.1.3.1) in serum as a potential tumor marker. We determined hPLAP in serum samples from 130 patients with ovarian cancer, 79 patients with testicular cancer (53 seminoma testis, 26 nonseminoma testis), 537 patients with various other malignant diseases (95 lung, 39 gastrointestinal, 195 breast, 208 others), 291 patients with benign diseases, and 213 healthy controls. To assess the influence of smoking on hPLAP activity in serum, we evaluated 79 serum samples from patients with noncancerous diseases for whom smoking habits had been recorded. Our main findings are: (a) hPLAP activity is frequently increased (greater than 100 mU/L) in pre-operative serum samples from ovarian cancer patients (49%) and from testicular cancer patients (59% overall; 72% seminoma, 35% nonseminoma); (b) heavy smoking may increase hPLAP activity; (c) excluding heavy smokers, a 96% specificity for cancerous lesions was observed; (d) in patients with ovarian malignancies, CA 125 and hPLAP may behave as independent markers; and (e) in patients with seminoma, hPLAP is clearly more frequently increased than is beta-choriogonadotropin.