Pembrolizumab Active in Few Soft Tissue, Bone Sarcoma Subtypes

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Pembrolizumab shows antitumor activity in osteosarcoma and undifferentiated pleomorphic sarcoma, but not other types of soft tissue sarcomas.
Pembrolizumab shows antitumor activity in osteosarcoma and undifferentiated pleomorphic sarcoma, but not other types of soft tissue sarcomas.
The following article features coverage from the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago, Illinois. Click here to read more of Cancer Therapy Advisor's conference coverage.

Pembrolizumab shows antitumor activity in osteosarcoma and undifferentiated pleomorphic sarcoma (UPS), but not other types of soft tissue sarcomas (STSs), according to a study that will be presented at the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago.1

The phase 2 SARCO028 trial evaluated pembrolizumab in cohorts with different types of STS and bone sarcomas (BS). The primary endpoint was objective response rate (ORR) by RECIST 1.1 criteria, and secondary endpoints included 12-week progression-free survival (PFS) and overall survival.

The trial enrolled 10 patients each in the cohorts with STS, including UPS, dedifferentiated liposarcoma (DDLPS), synovial sarcoma (SS), and leiomyosarcoma (LMS), and 40 patients with BS, including osteosarcoma, Ewing sarcoma (ES), or dedifferentiated chondrosarcoma (CS).

The ORR was 18% and the 12-week PFS was 55% (95% CI, 42-71%) during a median follow-up of 14.5 months among the overall STS cohort, but there was high variability among the STS subtypes. The greatest response was seen among patients with UPS, with an ORR of 40%, which included 1 complete response (CR) and 3 partial responses (PRs) among 10 patients. There were 2 and 1 PRs among patients with DDLPS and SS, respectively, and no CRs.

There were no responses among patients with LMS.

The ORR was 5% with a 12-week PFS of 28% (95% CI, 14-41%) among patients with BS during a median follow-up of 12.3 months. There was 1 PR each among patients with osteosarcoma and CS, and no responses among patients with ES. There were no CRs in the BS cohort.

There were 3 (4%) tumors positive for PD-L1 expression among 70 pre-pembrolizumab biopsies, all of which had CD8+ T-cell infiltration. All of the PD-L1–positive tumors were from patients with UPS.

RELATED: Do Specialized Cancer Centers Improve Outcomes for Patients With Ewing Sarcoma?

The investigators stated expansion cohorts are planned in the cohorts with UPS and LPS.

Read more of Cancer Therapy Advisor's coverage of the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting by visiting the conference page.

Reference

  1. Burgess MA, Bolejack V, Van Tine BA, et al. Multicenter phase II study of pembrolizumab (P) in advanced soft tissue (STS) and bone sarcomas (BS): final results of SARC028 and biomarker analyses. J Clin Oncol. 2017;35(suppl; abstr 11008).

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