As reported in the Journal of Clinical Oncology by Chen et al, extended follow-up of the pivotal phase II trial of atezolizumab in patients with alveolar soft part sarcoma (ASPS) showed continued benefit of atezolizumab treatment.
Study Details
In the U.S. multicenter trial, 53 patients received atezolizumab at 1,200 mg every 21 days. Any patient with no progression with ≥ 2 years of monotherapy was eligible for a monitored drug holiday for up to 2 years. Patients with disease progression could elect to have bevacizumab added to their atezolizumab therapy. The current report represents an additional 3 years of observation since the primary analysis.
Key Findings
After extended follow-up, the objective response rate of 35.8% (95% confidence interval [CI] = 23.1%–50.2%) and median progression-free survival of 20.8 months (interquartile range [IQR] = 7.6 months to not reached) remained similar to values at primary analysis. Median duration of response increased to 37.0 months.
ASPSCR1::TFE3 fusion type was determined for 47 of 53 patients: objective response rate (43.9%, 95% CI = 28.5%–60.2%) and median progression-free survival (28.3 months, IQR = 9.2 months to not reached) were higher among 41 patients expressing type 1 than among 6 patients expressing type 2 (0%, 95% CI = 0%–45.9%, and 7.5 months, IQR = 3.9 months to not reached; progression-free survival hazard ratio = 3.2, 95% CI = 1.01–10.2).
Among 11 patients who chose a per-protocol drug holiday (range = 3.5–26.4 months) after ≥ 2 years of treatment, 2 had disease progression during the holiday. Among nine eligible patients who elected to receive bevacizumab plus atezolizumab after disease progression, objective response rate was 0% and median progression-free survival was 18.5 months (IQR = 7.9–21.1 months).
The investigators concluded: “Long-term results support using atezolizumab to treat ASPS, even for several years; a drug holiday with careful monitoring may be an option for some patients.”
Alice P. Chen, MD, of Division of Cancer Treatment and Diagnosis, National Cancer Institute, Bethesda, Maryland, is the corresponding author for the Journal of Clinical Oncology article.
DISCLOSURE: The study was supported by the Intramural Research Program of the National Institutes of Health and the National Cancer Institute. For full disclosures of the study authors, visit ascopubs.org.
