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.”
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.
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 nejm.org.The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.