Immunotherapy

Approximately 70% to 80% of MCC cases in the United States are caused by Merkel cell polyomavirus (MCPyV). Within virus-positive MCCs, the viral oncoproteins (T antigens) are constitutively expressed and promote growth. Furthermore, patients with stimulated immune responses to MCPyV have better disease outcomes, providing a rationale for the use of immunotherapy. Although limited by a lack of randomized trials, several single-agent immune checkpoint inhibitors have shown improved survival and tolerability in patients with advanced MCC, compared with the chemotherapy that was used in historical controls. Therefore, immune checkpoint inhibitors are considered the recommended first-line treatment for most patients. There are ongoing trials to assess the use of immune checkpoint inhibitors in the neoadjuvant and adjuvant setting.