Trabectedin (T) as second line treatment option for patients with epithelioid malignant pleural mesothelioma (MPM) in progression following pemetrexed/platin-derivates chemotherapy: ATREUS trial.

Abstract

8513 Background: Systemic chemotherapy in MPM is inevitably followed by relapse, and response rates to second line treatment are limited. T is an antineoplastic agent targeting both the malignant cells and the tumor microenvironment with demonstrated activity against a range of tumors. We aimed to study the activity and safety of T in advanced MPM. Methods: ATREUS, an Italian multicenter single arm phase II trial, assessed the activity T in MPM evaluating the proportion of patients responding to treatment and achieving progression free survival for 12 weeks (PFS12w). Pre-treated epithelioid and naive or pre-treated biphasic/sarcomatoid pts were treated until progression or unacceptable toxicity. Initial dose was 1.3 mg/m2, over 3 hours every 21 days, later reduced to 1.1 mg/m2to improve tolerability. In the epithelioid cohort, sample size was based on a Simon's Optimal Two-Stage Design. The study was set to reject, at an alpha error of 10% the hypothesis that PFS12w was ≤25% and to demonstrate, with a power of 85% the hypothesis that PFS12w was ≥40%. At least 20 out of 62 pts with assessed disease, no major protocol violations, either receiving ≥12 weeks of treatment or interrupting before for progression or death (per protocol – PP analysis) were to reach PFS12w in order to consider T effective. Results: 71 pts were enrolled and evaluable. Average age was 65.8 ± 8.75 years. 71.8% were male and 82.5% presented stage III or IV disease. 42.4% (25/59) of pts included in the PP analysis obtained PFS12w (95% CI: 29.6% - 55.9%). In a second, more conservative analysis, including pts withdrawn prematurely for toxicity or intercurrent illness as failures, PFS12w rate reached 38.5% (25/65 pts). The most frequent grade ≥3 treatment-related toxicities werehepatic toxicity (60.5%), non-febrile neutropenia (21.1%), and fatigue (6.6%). Five pts (7%) interrupted treatment for toxicities (2 liver, 1 multi-organ failure, 1 thrombocytopenia, 1 T intolerance). Conclusions: In pts with advanced epithelioid MPM, second line treatment with T showed an elevated rate of disease stabilization. Safety data is promising but require further evaluation. Clinical trial information: NCT02194231.