Persistent low-level "real" human chorionic gonadotropin: a clinical challenge and a therapeutic dilemma.

OBJECTIVE: The finding of persistent low-level human chorionic gonadotropin (hCG) with or without a preceding pregnancy event presents a rare but clinically important challenge and a therapeutic dilemma. These are patients with "real" hCG shown by the positive test in both serum and urine or by specialized testing. The problems associated with "phantom" hCG have been recognized and should now be clinically resolvable. Four cases of low-level "real" hCG are described to illustrate the problems encountered, the management, and the resolution achieved.

METHODS: Two patients presented with persistent low-level hCG after hydatidiform mole pregnancy, one after an early pregnancy loss and one as amenorrhea and irregular bleeding. A detailed clinical description is provided to illustrate the difficulties encountered.

RESULTS: All patients have real hCG. The hCG level of Patient 1 was responsive to hormonal contraception and disappeared with such medication. Over a period of 3 years hCG reappeared whenever estrogen was stopped. Patient 2 achieved two pregnancies and the hCG subsequently disappeared. The hCG in Patient 3 persisted over a period of 6 years although she is now menopausal. Patient 4 developed metastatic placental site trophoblastic tumor after 2 1/2 years of observation of low-level hCG.

CONCLUSIONS: The finding of unexplainable low-level hCG in a patient without evidence of a uterine lesion or of trophoblastic metastases provides a therapeutic challenge. The administration of single-agent chemotherapy had no effect on the level of hCG in the three patients to whom it was administered. The administration of multiple-agent chemotherapy appears unjustified in the absence of a demonstrable trophoblastic tumor. A small number of trophoblastic cells must be providing this hCG and these cells may be quiescent for years. Nevertheless these cells may proliferate and manifest themselves as trophoblastic tumor. Continuing long-term surveillance of these patients is necessary.