Efficacy analysis of single-agent carboplatin AUC4 2-weekly as second-line therapy for methotrexate-resistant (MTX-R) low risk gestational trophoblastic neoplasia (GTN).

BACKGROUND:Approximately one-third of patients with low-risk Gestational Trophoblastic Neoplasia (WHO 0-6) develop methotrexate-resistance (MTX-R). In the UK, subsequent treatment with either actinomycin-D (ActD) or multi-agent combination chemotherapy has depended on whether the hCG was above or below an hCG threshold. To reduce exposure to combination chemotherapy (CC), over the years the UK service has raised this threshold as well as using single-agent carboplatin AUC6 3-weekly at MTX-R instead of CC. Updated results for carboplatin demonstrate an 86% complete hCG response (hCG CR) but associated with haematological dose-limiting toxicity. METHODS:In 2017, single-agent carboplatin became the national standard second-line treatment following MTX-R at hCG of >3000 IU/L. Carboplatin was changed to two-weekly AUC4 scheduling and continued until normal hCG plus 3 consolidation cycles. For patients failing to respond, CC (Etoposide-Actinomycin-D or EMA-CO) was introduced. RESULTS:22 evaluable patients with a median hCG at MTX-R of 10,147 IU/L (IQR 5527-19,639) received carboplatin AUC4 2-weekly (median no. of cycles = 6, IQR 2-8). Of these, 36% achieved a hCG CR. All 14 non-CR patients were cured with subsequent CC; 11 and 2 patients with 3rd line and 4th line CC respectively and 1 patient following 5th line CC and hysterectomy. Overall survival remains 100%. CONCLUSION:Carboplatin is not sufficiently active in the second-line treatment of low-risk MTX-resistant GTN. New strategies are required to increase hCG CR and spare more toxic CC regimens.