<prompt> Indications for instituting single-agent chemotherapy following evacuation of a hydatidiform mole usually includeA rise in hCG titersA plateau of hCG titers for 1 weekReturn of hCG titer to normal at 6 weeks after evacuationAppearance of liver metastasis  <response>: Mishell, 3e, pp 455-456. Single-agent chemotherapy is usually instituted if levels of hCG remain elevated 8 weeks after evacuation of a hydatidiform mole. Approximately 50 of the patients who have persistently high hCG titers will develop malignant sequelae. If hCG titers rise or reach a plateau for 2 to 3 successive weeks following molar evacuation, a single-agent chemotherapy should be instituted, provided that the trophoblastic disease has not metastasized to the liver or brain. The presence of such metastases usually requires initiation of combination chemotherapy. 