Cutaneous squamous cell carcinoma (CSCC) is the second most common skin cancer. Treatment of advanced CSCC has traditionally been performed with chemotherapies with predominately poor results. Recently Immunotherapy (IO) has shown promising effectiveness, however the overall survival reported from these trials is immature (i.e. median is yet to be reached). This poses challenges for payers and decision makers as economic modelling and evaluation are heavily dependent on overall survival (OS). The objective of this study is to identify surrogate endpoints for OS that can be used to establish whether next generation therapies are cost-effective for CSCC.