Merkel Cell Carcinoma

Abstract

Merkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine skin cancer that is highly radiosensitive and immunogenic. Immunotherapy is the primary treatment of advanced disease, and immune checkpoint inhibitors show promise as neoadjuvant or adjuvant therapy in patients with high-risk resectable MCC. Emerging biomarkers of tumor burden are becoming increasingly important in identifying high-risk patients and in post-treatment surveillance. Further research is needed to determine the optimal duration of anti-PD-(L)1 treatment and second-line options for patients with MCC refractory to immunotherapy. This review covers the characteristics and management of MCC including recent innovations and areas of active investigation.

Keywords: Immunotherapy; Merkel cell carcinoma; Merkel cell polyomavirus; Neuroendocrine; Skin cancer.

Figure 1.

MCC Treatment Algorithm. *PET/CT is preferred. ^†ctDNA^, and AMERK have demonstrated promising early results but are not yet recommended by treatment guidelines. ^‡For patients ineligible for surgery. ^§If clinical suspicion remains high. ^¶If high risk for false negative SLNB. Abbreviations: SLNB, sentinel lymph node biopsy; RT, radiotherapy; ICI, immune checkpoint inhibition; FNA, fine needle aspiration; Bx, biopsy; CLND, complete lymph node dissection.