Approximately one-third of patients with advanced alveolar soft part sarcoma (ASPS) — a rare soft-tissue sarcoma with a poor prognosis and no established therapy — had sustained responses to treatment with the anti–programmed death ligand 1 (PD-L1) agent atezolizumab, researchers report. “The results of this phase 2 clinical study, which formed the basis of the recent FDA approval, support the use of atezolizumab as a safe and effective treatment for advanced ASPS,” the investigators conclude. “Further investigation is needed to inform clinical decisions regarding the duration of atezolizumab treatment, the usefulness and appropriate timing of treatment breaks, and the potential benefit of atezolizumab rechallenge after disease progression.”
Atezolizumab 1200 mg (in patients ≥18 years of age) or 15 mg/kg with a 1200-mg cap (in patients <18 years of age) was administered intravenously once every 21 days. Study endpoints included objective response, duration of response, and progression-free survival, as well as pharmacodynamic biomarkers of multistep drug action.
“A total of 52 patients were evaluated,” the authors wrote. “An objective response was observed in 19 of 52 patients (37%), with 1 complete response and 18 partial responses. The median time to response was 3.6 months (range, 2.1 to 19.1), the median duration of response was 24.7 months (range, 4.1 to 55.8), and the median progression-free survival was 20.8 months. Seven patients took a treatment break after 2 years of treatment, and their responses were maintained through the data-cutoff date. No treatment-related grade 4 or 5 adverse events were recorded. Responses were noted despite variable baseline expression of programmed death 1 and PD-L1.”