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Pembrolizumab Shows Durable Antitumor Activity in Both Locally Advanced and Recurrent/Metastatic Squamous Cell Carcinomas


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The results of the second interim analysis of the KEYNOTE-629 study of pembrolizumab in cutaneous squamous cell carcinoma confirmed durable antitumor activity in both the locally advanced and the recurrent/metastatic settings. Adverse events with pembrolizumab were generally consistent with its established safety profile. Brett G.M. Hughes, MD, and colleagues reported in Annals of Oncology that based on their study results, pembrolizumab is a promising treatment option for patients with advanced cutaneous squamous cell carcinoma.

Brett G.M. Hughes, MD

Brett G.M. Hughes, MD

Cutaneous squamous cell carcinoma is the second most common nonmelanoma skin cancer, representing approximately 20% of all nonmelanoma skin cancers and 20% of all skin cancer–related mortalities. It has high tumor mutational burden and may be responsive to immunotherapy. The authors wrote in the study background that targeting the PD-1 pathway seems to be an effective option for recurrent/metastatic or unresectable locally advanced cutaneous squamous cell carcinoma.

KEYNOTE-629 Details

KEYNOTE-629 is a global, open-label, nonrandomized phase II study of patients with locally advanced or recurrent/metastatic cutaneous squamous cell carcinoma conducted at 59 centers. Eligible patients received pembrolizumab at 200 mg intravenously every 3 weeks for up to 35 cycles. The study’s primary endpoint was objective response rate by blinded independent central review per Response Evaluation Criteria in Solid Tumors version 1.1. Secondary endpoints included duration of response, disease control rate, progression-free survival, overall survival, and safety and tolerability. Efficacy and safety were analyzed in patients who were treated with at least one dose of pembrolizumab.

Based on the first interim analysis, the KEYNOTE-629 investigators concluded that pembrolizumab demonstrated clinically meaningful and durable antitumor activity with a manageable safety profile in patients with recurrent/metastatic cutaneous squamous cell carcinoma. They are now reporting the results from the second interim analysis, including initial data for the locally advanced cohort and updated data for the recurrent/metastatic cohort.

Updated Results

Between November 2017 and September 2019, 159 patients were enrolled and treated with pembrolizumab—54 in the locally advanced cohort and 105 in the recurrent/metastatic cohort. The median time from the first dose to data cut-off in July 2020 was 14.9 months in the locally advanced cohort and 27.2 months in the recurrent/metastatic cohort.

In the locally advanced cohort, the objective response rate was 50.0% (95% confidence interval [CI] = 36.1%–63.9%); 16.7% patients achieved complete response and 33.3% achieved a partial response. In the recurrent/metastatic cohort, the objective response rate was 35.2% (95% CI = 26.2%–45.2%); 10.5% patients achieved complete response and 24.8% achieved partial response. Median duration of response was not reached in either cohort.

Grade 3 to 5 treatment-related adverse events occurred in 11.9% of patients.

Study limitations included the single-arm design and the small number of patients who received pembrolizumab as first-line treatment in the recurrent/metastatic cohort. 

The authors concluded, “The robust antitumor activity of pembrolizumab in both locally advanced and recurrent/metastatic cutaneous squamous cell carcinoma was confirmed and demonstrated to be durable without unexpected safety signals.”

Disclosure: The study was funded by Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc. For full disclosures of the study authors, visit annalsofoncology.org.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
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