Pembrolizumab in Combination with Radiotherapy for Metastatic Melanoma - Introducing the PERM Trial

Single-agent PD-1 inhibitors are the mainstay of systemic treatment for patients with metastatic melanoma. Response rates to single-agent pembrolizumab and nivolumab range from 30 to 45% [1]. Combination treatment, with CTLA-4 and PD-1 inhibitors, improves the response rate to 58%, at the expense of increased treatment-related toxicities, which may be intolerable for some [2]. Hence, a significant proportion of these patients may benefit from different combinations of immune checkpoint modulators and conventional therapies, and the design of these combinations may be guided by understanding the immune microenvironment of the tumour [3].