Therapeutic Cancer Vaccines for Nonmelanoma Skin Cancer

The development of immunotherapies for nonmelanoma skin cancer (NMSC) has lagged far behind that for melanoma in the past few decades, given that the majority of cases are surgically curable. Nevertheless, given the steady growth in the incidence rate of NMSC and attendant increase in patients with unresectable or advanced-stage tumors, the demand for systemic therapy is noticeably increasing. To date, the most widely used immunotherapeutic strategies, including immune checkpoint inhibitors and T-cell therapy, have obtained satisfactory results in some patients but not others. Even with an objective response in a fraction of patients, some accompanying adverse events may lead to intolerance and noncompliance. The expanding understanding of immune surveillance and tumor escape has provided us with novel perspectives in the field of immunotherapy. One emerging approach, the therapeutic cancer vaccine, encompasses the potential to newly "prime" T cells by activating antigen presentation in regional lymph nodes and the tumor microenvironment. Immune cells are therefore preconditioned and awakened to be ready to attack tumors. In NMSCs, multiple clinical trials of cancer vaccines are underway. The vaccine targets include tumor-associated antigens, tumor-specific antigens, oncolytic viruses, and toll-like receptors. Although clinical benefits have been shown in specific case reports and trials, various challenges remain to be resolved to guarantee applicability in the general patient population. Standing on the shoulders of pioneers expedites the pace of advances in therapeutic cancer vaccines, making them the rising star in the field of immunotherapy.