Serum human chorionic gonadotropin ratios for the detection of etoposide, methotrexate, dactinomycin, cyclophosphamide, and vincristine resistance in high-risk gestational trophoblastic neoplasia.

A hCG ratio of <31.9 at the fourth cycle should be considered a high-risk for etoposide, methotrexate, dactinomycin, cyclophosphamide, and vincristine resistance and may need second-line chemotherapy. The ratio increases the detection rate of resistance to these drugs more than the traditional criteria.