522 Comparison of efficacy and adverse events of 2 ACT-D regimens in the treatment of low-risk gestational trophoblastic neoplasia: a retrospective study

Introduction/Background Low-risk gestational trophoblastic neoplasia (GTN) is treated with single-agent chemotherapy. In Europe, methotrexate with folinic acid rescue (MTX/FA) is the usual first-line therapy, and in the event of resistance, a switch is made to dactinomycin (ACT-D). There are two regimens of ACT-D, the 5-day regimen and the biweekly pulsed regimen. There are no large cohort studies to investigate the differences in efficacy or chemotoxicity between the two regimens and to support the choice of treatment. The aim of this study was to assess the differences in primary cure, recurrence and chemotoxicity between the 5-day ACT-D regimen and the biweekly pulsed ACT-D regimen. Methodology A retrospective study was performed using the database of the Charing Cross Center for Gestational Trophoblastic Disease. Patients treated with ACT-D as second line treatment for low-risk GTN between 1993–2020 were selected. Results In total 324 patients were included, of which 180 received the 5-day ACT-D regimen and 144 received the biweekly pulsed ACT-D regimen. Resistance occurred in 24 patients (7.4%), cure was achieved in 168/180 (93%) in the 5-day group and in 132/144 (92%) in the biweekly pulsed group, which was not significantly different (p=0.569). After completion of treatment a total of 18 patients (5.5%) had a recurrence. Of these patients 8/180 (4%) had received the 5-day regimen and 10/144 (7%) patients had received the bi-weekly pulsed regimen, which was not significantly different (p=0.283). None of the patients reported a severe adverse event. Conclusion There is no significant difference in the primary cure, recurrence rate or chemotoxicity between the 5-day ACT-D regimen and the biweekly pulsed ACT-D regimen. Given the need for fewer visits and reduced health care costs, the latter regime seems the most beneficial. Disclosures Nothing to disclose.