Comparison of 5-day MTX and 5-day ETP treatment results and early predictors of drug resistance to 5-day MTX in patients with post-molar low-risk gestational trophoblastic neoplasia

Abstract Objective To determine the primary remission rates and predictors of drug resistance in patients with post-molar low-risk gestational trophoblastic neoplasia (GTN) who were treated with a 5-day intramuscular methotrexate (5-day IM MTX) or a 5-day drip infusion etoposide (5-day DIV ETP) regimen. Methods Between 1980 and 2014, 166 consecutive patients with low-risk post-molar GTN were initially treated with a 5-day IM MTX or a 5-day DIV ETP regimen. The primary remission rates, changes in chemotherapy due to drug resistance or toxicity, and relapse rates were compared. Furthermore, we analyzed the factors that influenced the development of resistance to MTX. Results Primary remission rates were significantly higher among the ETP-treated patients than among the MTX-treated patients. Among the 42 patients who required a change in chemotherapy, 23 patients (22.6%) and 4 patients (6.3%) were diagnosed as being resistant to MTX and EPT, respectively. Maternal age and the presence of metastasis did not significantly influence the development of MTX resistance, although higher FIGO scores and pre-treatment human chorionic gonadotropin (hCG) levels of > 5 × 104 mIU/mL were significantly more common among patients who developed MTX resistance. Moreover, a < 30% decrease in hCG after the first cycles of MTX chemotherapy was significantly associated with the development of MTX resistance. Conclusions All patients with low-risk GTN eventually achieved complete remission, although several patients developed drug resistance to the first-line chemotherapy. A < 30% decrease in hCG during the first chemotherapy cycle may be an early indicator of drug resistance after commencing a 5-day MTX regimen.