Blocking PD-1/PD-L1 axis with ICIs for the treatment of advanced MCC has achieved anti-tumor activity in ~ 30–60% of the patients as well as improvement in PFS and OS compared to patients receiving chemotherapy.52–55 Indeed, data from retrospective analyses confirmed the optimistic overview to continue using ICIs for the treatment of metastatic MCC patients.52,56 This study evaluated patients from two large academic medical centers who were treated with alternative ICIs after progressive disease (PD). Here, PDCD1 is linked to Merkel cell skin cancer.