 Gestational trophoblastic disease comprises a spectrum of diseases with different propensity for local invasion and metastasis, that is, partial and complete hydatidiform mole, choriocarcinoma, and placental site trophoblastic tumor.All trophoblastic tumors produce hCG, and monitoring of therapy is largely based on the determination of hCG in serum. The conformational change of tumor markers during antineoplastic chemotherapy for cancer and its clinical meaning has only been rarely studied. In this study, we will try to understand the conformational change of the tumor marker hCG during chemotherapy. 