Atezolizumab for Alveolar Soft Part Sarcoma: A Clinical Trial Update

Area of Science:

• Oncology
• Medical Research
• Clinical Trials

Background:

• Alveolar soft part sarcoma (ASPS) is a rare soft tissue sarcoma.
• Atezolizumab is an immunotherapy agent targeting PD-L1.
• Previous studies indicated potential efficacy of atezolizumab in ASPS.

Purpose of the Study:

• To report long-term outcomes of atezolizumab in ASPS patients.
• To evaluate the impact of ASPSCR1::TFE3 fusion type on treatment response.
• To assess the feasibility and outcomes of a drug holiday and combination therapy.

Main Methods:

• Phase II clinical trial (NCT03141684) with 53 ASPS patients.
• Patients received atezolizumab treatment.
• ASPSCR1::TFE3 fusion typing was performed; subgroups analyzed for response and survival.

Main Results:

• Median duration of response increased to 37.0 months.
• Objective response rate (ORR) was 35.8% and median progression-free survival (mPFS) was 20.8 months.
• Patients with ASPSCR1::TFE3 type 1 fusion showed higher ORR (43.9%) and mPFS (28.3 months) compared to type 2 (ORR 0%, mPFS 7.5 months).
• Drug holidays were feasible for 11 patients; 2 progressed during the holiday.
• Bevacizumab plus atezolizumab combination therapy in 9 patients yielded 0% ORR and 18.5 months mPFS.

Conclusions:

• Long-term atezolizumab treatment is supported for ASPS.
• ASPSCR1::TFE3 fusion type influences treatment outcomes.
• Drug holidays with monitoring may be a viable option for select ASPS patients.
• Bevacizumab plus atezolizumab showed limited efficacy in this small cohort.