A single-arm multicentre phase II trial of doxorubicin in combination with trabectedin in the first-line treatment for leiomyosarcoma with long-term follow-up and impact of cytoreductive surgery

Background: Uterine leiomyosarcomas (U-LMSs) and soft tissue leiomyosarcomas (ST-LMSs) are rare tumours with poor prognosis when locally advanced or metastatic, and with moderate chemosensitivity. In 2015 we reported very encouraging results of the LMS-02 study (NCT02131480) with manageable toxicity. Herein, we report the updated and long-term results of progression-free survival (PFS) and overall survival (OS). Patients and methods: Patients received 60 mg/m² intravenous doxorubicin followed by trabectedin 1.1 mg/m² as a 3-h infusion on day 1 and pegfilgrastim on day 2, every 3 weeks, up to six cycles. Surgery for residual disease was permitted. Patients were stratified into U-LMS and ST-LMS groups. Results: One-hundred and eight patients were enrolled, mainly with metastatic disease (85%), and 20 patients (18.5%) had surgical resection of metastases after chemotherapy. With a median follow-up of 7.2 years [95% confidence interval (CI) 6.9-8.2 years], the median PFS was 10.1 months (95% CI 8.5-12.6 months) in the whole population, and 8.3 months (95% CI 7.4-10.3 months) and 12.9 months (95% CI 9.2-14.1 months) for U-LMSs and ST-LMSs, respectively. The median OS was 34.4 months (95% CI 26.9-42.7 months), 27.5 months (95% CI 17.9-38.2 months), and 38.7 months (95% CI 31.0-52.9 months) for the whole population, U-LMSs, and ST-LMSs, respectively. The median OS of the patients with resected metastases was not reached versus 31.6 months in the overall population without surgery (95% CI 23.9-35.4 months). Conclusions: These updated results confirm the impressive efficiency of the doxorubicin plus trabectedin combination given in first-line therapy for patients with locally advanced/metastatic LMS in terms of PFS and OS. Results of the LMS04 trial (NCT02997358), a randomized phase III study comparing the doxorubicin plus trabectedin combination versus doxorubicin alone in first-line therapy in metastatic LMSs, are pending.