PD-L1 Inhibition for Advanced Alveolar Soft-Part Sarcoma

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In a phase II trial reported in The New England Journal of Medicine, Chen et al found that atezolizumab produced durable responses in patients with advanced alveolar soft-part sarcoma.

As stated by the investigators: “Alveolar soft-part sarcoma is a rare soft-tissue sarcoma with a poor prognosis and no established therapy. Recently, encouraging responses to immune checkpoint inhibitors have been reported.”

Study Details

In the United States–based, investigator-initiated, multicenter trial, 52 patients who had received no prior PD-1 or PD-L1 inhibitors were enrolled between April 2017 and July 2022. They were treated with atezolizumab at 1,200 mg for those aged 18 and older (n = 49) or 15 mg/kg (maximum dose of 1,200 mg) for those aged up to 18 (n = 3) every 3 weeks. A total of 27 patents had received at last one prior line of systemic therapy.  

Key Findings

Among the 52 patients, objective response was observed in 19 patients (37%, 95% confidence interval [CI] = 24%–51%), with a complete response in 1. Median time to response was 3.6 months (range = 2.1–19.1 months). Median duration of response was 24.7 months (range = 4.1–55.8 months). Seven responding patients took a treatment break after 2 years on treatment, with all maintaining a response at last analysis.

A total of 28 patients (54%) had stable disease as best response. Median best change from baseline in tumor size was −66.2% (range = −36.6% to −100%). Median progression-free survival was 28 months. Responses were observed irrespective of baseline PD-1 or PD-L1 expression.

Grade 1 or 2 adverse events occurred in 50 patients (96%). Treatment-related grade 3 adverse events occurred in eight patients (15%), with no grade ≥ 4 events being observed. No patients discontinued treatment because of adverse events. 

The investigators concluded: “Atezolizumab was effective at inducing sustained responses in approximately one-third of patients with advanced alveolar soft-part sarcoma.”

Alice P. Chen, MD, of the Division of Cancer Treatment and Diagnosis, National Cancer Institute, is the corresponding author of The New England Journal of Medicine article.

Disclosure: The study was funded by the National Cancer Institute and others. For full disclosures of the study authors, visit

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