A single-arm multicenter phase II trial of doxorubicin (Doxo) in combination with trabectedin (Trab) given as first-line treatment to patients with metastatic/advanced uterine (U-LMS) and soft tissue leiomyosarcoma (ST-LMS): Final results of the LMS-02 study

11506 Background: U-LMS and ST-LMS are rare tumors with poor prognosis when locally advanced or metastatic, and with moderate chemosensitivity. Overall response rates (ORR) given in the 1st-line setting do not exceed 50% for U-LMS and 35% for ST-LMS with a mean response duration of 3- 6 months without impact on overall survival (OS). In 2015 we reported very encouraging results of the LMS-02 study (NCT02131480) with ORR of 59.6% in U-LMS, and 39.3% in ST-LMS with manageable toxicity (Pautier; Lancet oncol 2015). Herein, we report the updated results of progression-free survival (PFS) and final results of overall survival (OS). Methods: Patients (pts) received 60 mg/m² intravenous Doxo followed by trabectedin 1.1 mg/m2 as a 3-hour infusion on Day 1 and pegfilgrastim on Day 2, repeated every 3 weeks for up to 6 cycles. Surgery for residual disease was permitted. Patients were stratified into U-LMS and ST-LMS groups. Results: Overall, 108 patients with LMS with a median age of 59 years and mostly metastatic disease (85%) were enrolled. Of those, 77 patients (71.3%) have received all 6 cycles of treatment, and 20 patients (18.5%) had metastasis resection. With a median follow-up of 7.2 years (95% CI: 6.9 - 8.2), the overall median PFS was 10.1 months (95% CI: 8.5 - 12.6), being 8.3 months (95 CI: 7.4 - 10.3) and 12.9 months (95% CI: 9.2 - 14.1) in U and ST group, respectively. Median OS was 34.4 months (95% CI: 26.9 - 42.7), being 27.5 months (95% CI: 17.9 - 38.2) in U-LMS and 38.7 months (95% CI: 31.0 - 52.9) in ST-LMS group. The median OS among the 20 pts with surgery was not reached vs 31.6 months in the population without surgery (95% IC: 23.9 - 35.4). Conclusions: The Doxo +Trab combination is an effective 1st-line therapy for pts with LMS, with promising PFS and OS results and an acceptable safety profile. Merely for comparison, the most recent results of Doxo alone in metastatic LMS, given in 1st-line setting in a phase III ANNOUNCE trial conducted during the same period, reported median PFS of 6.9 months, and median OS of 21.9 months (ASCO 2019 LBA3). Results of the LMS04 trial (NCT02997358), a randomized phase III study comparing this combination vs Doxo alone in 1st-line therapy in metastatic LMS are pending. Clinical trial information: NCT02131480 .