Trophoblastic cell sensitivity to 8-day chemotherapy in nonmetastatic gestational trophoblastic neoplasia.

Serial radioimmunoassay determinations of serum beta hCG and methotrexate were compared in two patients with nonmetastatic gestational trophoblastic neoplasia (NMGTN) treated with Goldstein's modification of Bagshawe's intermediate-dose methotrexate-citrovorum factor rescue-treatment program. Pretreatment beta hCG levels (mIU/ml) ranged within the outer limits of the 10(3) log level. Following intravenous methotrexate, sharp serum peaks between 10(-6) and 10(-5) M were observed. Plasma disappearance was rapid with a 3 log drop noted within 24 hr to levels incapable of inhibiting DNA synthesis. beta hCG levels manifested a 1 to 1.5 log drop over the 8 days of chemotherapy and complete remission was noted within 5 to 6 weeks of the first dose of methotrexate. No significant clinical or laboratory toxicity was observed. Although cell culture studies show that 100% of cell death can be achieved with serum levels of 10(-5) M in methotrexate-resistant choriocarcinoma, similar data do not exist for previously untreated trophoblastic neoplastic cells. These preliminary observations suggest that serum methotrexate levels are important for establishing sensitivity levels in a heterogeneous population of trophoblastic cells in NMGTN and that the total dose of methotrexate may be safely preselected on the basis of the pretreatment beta hCG.