Phase II trial of pembrolizumab (MK-3475) in metastatic cutaneous squamous cell carcinoma: An updated analysis.

Abstract

e21015 Background: Cutaneous squamous cell carcinomas (cSCC) are generally curable with surgery and/or radiation. Unfortunately, some patients develop locally advanced or metastatic disease, with an estimated 3900 to 8700 patients dying of cSCC in 2012. Aggressive disease is often associated with immunosuppression, and no treatment has shown an improvement in overall survival (OS). Recently the FDA has approved cemiplimab-rwlc which targets PD-1. This abstract provides an updated analysis and additional followup for patients treated with pembrolizumab which also targets PD-1. Methods: Clinical activity of pembrolizumab in cSCC patients was evaluated in patients who were not curable by surgery and/or radiation. Patients were treated with pembrolizumab 200mg IV every 3 weeks for up to 2 years. Tumor response was measured every 12 weeks using RECIST version 1.1. Response rate (RR) of pembrolizumab in metastatic cSCC was the primary objective. 6-month progression-free survival (PFS) and 1 year OS were secondary objectives. Results: 11 subjects have been enrolled thus far with a median age of 70.3 years. Two were female and all were Caucasian. ORR per RECIST criteria was 64% with 18% (2) having a complete response, 36% (4) a partial response, 36% (4) progressive disease (PD), and 9% (1) stable disease. The patient with stable disease had a clinical response and was eventually able to undergo surgery that rendered him without any evidence of disease. 6 month PFS for evaluable patients was 72%. Of those patients with a response, 50% had a durable response of 18 months or greater at the time of data cut-off. No subject deaths have occurred on study. Three grade 3 related-adverse events were noted (hepatitis and pneumonitis). Conclusions: Pembrolizumab is active in advanced cSCC. Responses appear durable and comparable to what has been seen in previous studies with the FDA-approved agent, cemiplimab. No new safety concerns were noted. Additional follow up is needed in order to establish an OS benefit. Clinical trial information: NCT02964559.