The following article features coverage from the European Society for Medical Oncology 2020 virtual meeting. Click here to read more of Cancer Therapy Advisor‘s conference coverage.

Treatment of some types of rare sarcomas with pembrolizumab resulted in durable clinical benefit among some patients, according to results of a nonrandomized phase 2 trial presented at the European Society of Medical Oncology (ESMO) Virtual Congress 2020.

Although immune checkpoint inhibitors have shown limited activity among unselected populations with sarcoma, sarcomas comprise more than 150 different diseases. The purpose of this study was to evaluate the efficacy and safety of pembrolizumab among patients with rare sarcoma subtypes.

The multicenter, single-arm phase 2 AcSé trial treated 81 patients with rare advanced sarcomas who were resistant to standard treatment with pembrolizumab for up to 2 years. The primary endpoint was objective response rate (ORR) and secondary endpoints included progression-free survival (PFS), overall survival (OS), duration of response (DOR), clinical benefit rate, and safety.

At baseline, the median patient age was 48 years, and 52% of participants were male. The median number of prior lines of therapy was 2. The rare sarcomas included in the analysis were chordoma (24 patients), alveolar soft-part sarcoma (ASPS; 14 patients), desmoplastic small round cell tumor (DSRCT; 5 patients), SMARCA4-malignant rhabdoid tumor (SMBT; 6 patients) and 26 different types of other rare sarcomas (32 patients).


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The ORR was 15%. The best response was partial response (PR); there were no complete responses. The rate of PR was different between the histotypes, with PR rates highest in ASPS at 35.7%, followed by SMBT at 33.3%, epithelioid sarcoma at 20%, the other group at 9%, and chordoma at 8%.

Overall, according to the study abstract, the median PFS was 7.9 months. PFS also varied among the histotypes (P =.013) with a median of 5.7, 14, 5, and 2.7 months for patients with chordoma, ASPS, DSCRCT, and others, respectively. The median PFS was not reached for patients with SMBT. The 1-year PFS rates were 35%, 58%, 0%, 62.5%, and 8%, respectively.

The median OS also varied by histology. As reported in the presentation abstract, the median OS was 20, 7.4, and 5.4 months for chordoma, DSRCT, and others, respectively. Median OS was not yet reached for the other histotypes. The 1-year OS rate was 72% for chordoma, 90% for ASPS, 50% for DSCRCT, 83% for SMBT, and 40% for others.

“These sarcomas are not consistently associated with PD-L1 expression, high [tumor mutational burden], cell infiltrates, or tertiary lymphoid structures,” Jean-Yves Blay, of the Comprehensive Cancer Centre of Lyon and Rhône-Alpes, France, and presenter of the study, said. Ongoing translational studies are ongoing to understand determinants of response.

Disclosures: The study was funded by MSD. Some of the presenters reported financial relationships with the pharmaceutical industry. For a full list of disclosures, please refer to the original abstract.

Read more of Cancer Therapy Advisor‘s coverage of the ESMO Virtual Congress 2020 by visiting the conference page.

Reference

Blay J-Y, Chevret S, Penel N, et al. High clinical benefit rates of single agent pembrolizumab in selected rare sarcoma histotypes: First results of the AcSé pembrolizumab study. Presented at: European Society of Medical Oncology (ESMO) Virtual Congress 2020; September 19-20, 2020. Abstract 1619O.