Nonmelanoma skin cancer (NMSC) is the most frequently diagnosed malignancy in humans, representing a broad range of cutaneous tumors. Keratinocyte carcinomas, including basal cell carcinoma (BCC) and cutaneous squamous cell carcinoma (CSCC), are the most common NMSCs. The incidence of BCC and CSCC is steadily increasing due to a progressively aging population, chronic exposure to ultraviolet radiation, and increased awareness with earlier diagnosis. Rarer NMSCs, such as Merkel cell carcinoma (MCC) and cutaneous adnexal carcinomas, are also on the rise. Although the majority of NMSC tumors are localized at diagnosis and managed effectively with curative surgery and radiation, in rare cases with nodal and distant metastases, systemic therapy is often required. As our understanding of the immunologic characteristics of NMSCs has improved, effective treatment options have expanded with the development of immunotherapy. The FDA recently approved several immune checkpoint inhibitors for the treatment of locally advanced and metastatic MCC, CSCC, and BCC. We review the emerging role of immunotherapy as the standard of care for several advanced NMSCs not amenable to surgery and/or radiation and underscore the need for considering clinical trials of novel strategies in patients when immunotherapy does not provide durable benefit. Finally, we explore the potential of neoadjuvant and adjuvant immunotherapy.

Merkel cell carcinoma (MCC) is a very rare but highly aggressive cutaneous neuroendocrine carcinoma and is associated with chronic exposure to ultraviolet light and the Merkel cell polyoma virus. The incidence rate of MCC is increasing and MCC is associated with high rates of recurrence and mortality. Immune checkpoint inhibitors (ICIs) offer durable responses and significant clinical benefit with 2 agents-avelumab (anti-PD-L1) and pembrolizumab (anti-PD-1)—currently approved by the U.S. Food and Drug Administration for the treatment of advanced MCC. Despite the advances in systemic therapy options for MCC, ~50% of patients with advanced MCC treated with ICI progress on therapy. There is a paucity of studies assessing second-line systemic therapy following primary/acquired resistance to ICIs. Current management in this setting remains a clinical challenge especially in trial ineligible patients. We evaluated objective response to ipilimumab plus nivolumab in metastatic MCC refractory to anti-PD-(L)1 therapy. Thirty-one percent of patients experienced a grade III or grade IV immune-related adverse event (irAE) due to ipilimumab plus nivolumab. No patients (0/13) achieved a complete or partial response via RECISTv1.1/irRECIST. Twenty-three percent (3/13) of patients achieved stable disease as the best overall response but progressed shortly thereafter. The median progression-free survival was 1.3 months (90% CI 1.1–1.5) from the initiation of ipi-nivo. The median overall survival was 4.7 months (95% CI 3–17). This study suggests limited, if any, clinical benefit of ipi-nivo in patients with advanced anti-PD-L1/anti-PD-1 refractory MCC.