Multicenter phase 2 trial of atezolizumab for advanced alveolar soft part sarcoma

Alveolar soft part sarcoma (ASPS) is a rare soft-tissue sarcoma with a poor prognosis and no established therapy. Recently, encouraging responses to immune checkpoint inhibitors have been reported. A multicenter phase 2 trial in the United States evaluated atezolizumab (anti-PD-L1) for advanced ASPS. An objective response was seen in 37% of the patients (one complete response), with median time to response 3.6 months (range 2.1 to 19.1) and median duration of response 24.7 months (range 4.1 to 55.8). Median progression-free survival was 20.8 months. Seven responding patients took a treatment break after 2 years of treatment, and their responses were maintained through the data-cutoff date. No treatment-related graad 4 or 5 adverse events were recorded. The authors conclude that atezolizumab was effective at inducing sustained responses in approximately one third of patients with advanced ASPS.