Immune checkpoint inhibitor: An emerging treatment for head and neck cancer. a primer for the radiologist

Immune checkpoint inhibitors have revolutionized treatment in many cancers, including head and neck squamous cell carcinoma. The number of drugs recently approved by the FDA and the European Medicine Agency is growing. Pembrolizumab and nivolumab, which are anti-programmed cell death protein 1 monoclonal antibodies, were first adopted in 2016 as the second-line treatment for recurrent or metastatic head and neck squamous cell carcinoma in patients with disease progression after platinum-based chemotherapy. Recently, pembrolizumab with or without platinum-based chemotherapy was approved as the first-line treatment for recurrent or metastatic head and neck squamous cell carcinoma. Imaging studies play an essential role in assessing treatment response and monitoring efficacy and safety during and after treatments. Given the rapid increase in the use of immunotherapy in head and neck squamous cell carcinoma, neuroradiologists need to be familiar with the unique features indicative of treatment response in addition to a broad array of immune-related adverse events to avoid misinterpreting secondary drug-related adverse effects as tumor progression or metastasis. Moreover, emerging imaging techniques, including molecular imaging and radiomics, in an effort to assess or gauge the likelihood of treatment response to immune checkpoint inhibitors, is an ongoing area of active research.