Monitoring therapy in trophoblastic diseases by radioimmunoassay of pregnancy-specific beta 1-glycoprotein and the beta subunit of human chorionic gonadotropin.

The beta-subunit of human chorionic gonadotrophin (hCG) and pregnancy-specific beta 1-glycoprotein (SP1) were measured simultaneously by specific radioimmunoassays in 473 serum samples from 43 patients with trophoblastic tumors. Both SP1 and hCG values were high in 16 untreated patients. 27 patients had been treated previously elsewhere, and their further treatment and monitoring were started simultaneously in our institute. Raised SP2 and hCG levels were found in 22 and 21 cases, respectively. Treatment was followed by a parallel decrease of both SP1 and hCG, but the hCG decline was more marked. Seronegativity was reached only after several months; SP1 was present in the serum for 60-150 days, and hCG could be found even after this time. Both parameters were sensitive indicators of residual tumor activity, calling for further therapy months before any clinical manifestation of recurrence. In three cases only one of the tumor makers could be found, which underlines the importance of the simultaneous measurement of hCG and SP1.