Serum methotrexate and human chorionic gonadotropin concentrations during five-day chemotherapy for low-risk metastatic gestational trophoblastic neoplasia.

A recent report of serum methotrexate (MTX) levels measured during treatment of gestational trophoblastic neoplasia (GTN) led us to determine MTX and human chorionic gonadotropin (beta-hCG) levels in a patient with low-risk metastatic GTN with a pulmonary metastasis. Peak MTX concentrations exceeded 10(-6) mol/l considered by many investigators to be within the therapeutic range against many human tumors. Serum beta-hCG levels did not decline during MTX administration; however, after 5 days of MTX a steep dose-response curve was observed which continued during 5 courses of chemotherapy.