(P 337) POOLED ANALYSIS OF TRABECTEDIN EFFICACY IN MYXOID/ROUND CELL LIPOSARCOMA FROM THREE PROSPECTIVE CLINICAL TRIALS

Objective: Trabectedin is a standard of care (SOC) chemotherapy for recurrent/metastatic liposarcomas (LPS). LPS include genetically distinct subtypes: well-differentiated/dedifferentiated, pleomorphic, and myxoid/round cell liposarcoma (MRCLS). Clinical trials often group subtypes, not typically reporting comprehensive outcomes for each. We performed a pooled analysis of trabectedin efficacy in MRCLS across multiple trials to serve as an SOC efficacy baseline.

Methods: The Yale University Open Data Access Project was queried for prospective trabectedin trials. Seven were identified; 4 excluded (3 had no means to reference MRCLS within the data, 1 was a neoadjuvant trial). Participant-level data on patients (pts) with locally unresectable/metastatic MRCLS who received ≥1 trabectedin dose (1.0–1.5 mg/m2 24 hrs continuous infusion every 3 wks) were extracted from 3 trials: ClinicalTrials.gov NCT00060944 (Phase 2), NCT00210665 (expanded access), and NCT01343277 (Phase 3). Primary outcome was overall response rate (ORR; complete response or partial response per RECIST v1.1). Secondary outcomes included disease control rate (DCR; ORR + stable disease [SD]), duration of response, overall survival (OS; time between first date of trabectedin treatment and death), and duration of SD for pts with available data. Responses were assessed using RECIST by investigators in NCT01343277 and by independent review in NCT00060944. In NCT00210665, tumor assessment followed institutional standards, so only OS was analyzed.

Results: Eligibility criteria required that pts were intolerant to or had relapsed/progressed after previous SOC cytotoxic chemotherapy. Sixty-three pts (42 from NCT01343277, 13 from NCT00060944, 8 from NCT00210665) were included: 32% (20/63) female, median age 50 (range, 20–75) yrs, and 79% (50/63) White. ORR was analyzed for 49 pts: 37 from NCT01343277, 12 from NCT00060944 (Table). For 22 pts with duration of SD data, 18 had SD ≥12 wks, 4 had SD < 12 wks; median duration of SD was 6.41 (range, 0.03–15.74) mo. OS data were available for 63 pts: median OS was 22.51 mo (95% CI: 16.99–34.33).

Conclusion: This represents one of the largest populations to date of pts with advanced MRCLS treated with trabectedin in prospective clinical trials. It is limited by typical factors affecting pooled analyses including heterogeneity across studies. Nevertheless, the results provide a trabectedin efficacy baseline against which to compare other therapies for MRCLS.

Best Overall Responses in 49 Pts with Advanced MRCLS Receiving Trabectedin.