Staging Before gestational trophoblastic disease is treated, it is assigned the following: A stage based on the 2000 International Federation of Gynecology and Obstetrics (FIGO) staging system (see table FIGO Anatomic Staging of Gestational Trophoblastic Neoplasia) A risk score based on the modified World Health Organization [WHO] prognostic scoring system (see table WHO Scoring System in Metastatic Gestational Trophoblastic Disease) Both systems correlate with clinical outcomes and identify patients at risk of treatment failure.