Single or two drug combination therapy as initial treatment for low risk, gestational trophoblastic neoplasia. A Canadian analysis.

INTRODUCTION: Low risk gestational trophoblastic neoplasia, WHO prognostic score of 0 to 6, is highly curable. There is no consensus on the optimal chemotherapy. Common regimens are q2wk actinomycin-D (ACT-D), weekly intramuscular methotrexate (MTX) or multi-day MTX. Combination MTX/ACT-D is rarely used. METHODS: A four centre, retrospective cohort study was carried out comparing commonly used regimens: weekly MTX, q2weekly ACT-D and q2 weekly MTX and ACT-D. RESULTS: 412 patients - 196 MTX/ACT-D, 107 MTX, 109 ACT-D - were treated between October 1994 and January 2019. Initial regimen failure (secondary to resistance or toxicity) occurred in 37% (MTX), 21% (ACT-D) and 5% (MTX/ACT-D). Relapse after completion of primary therapy (initial plus switch to another therapy if needed) was rare (0-5%). All eventually were cured. Mean number of cycles required to achieve remission were 10.1 (MTX), 7 (ACT-D) and 5.6 (MTX/ACT-D) with corresponding mean treatment durations of 3.12, 2.9 and 2.26 months. Dosage reductions occurred in 3% (MTX), 0% (ACT-D) and 29% (MTX/ACT-D). Higher failure rates occurred with WHO prognostic scores of 5 to 6 and HCG levels ≥10,000. SUMMARY: Initial regimen failure ie the need to switch to an alternative treatment was more common with MTX. ACT-D and MTX/ACT-D were similar within prognostic score 0-4 or HCG < 10,000. ACT-D then appears the better initial choice with its superior convenience. Above these levels primary failure rates are less with MTX/ACT-D, making it a better choice.