A Phase 3, Randomized, Double-blind, Placebo-controlled Study to Evaluate Pembrolizumab Versus Placebo as Adjuvant Therapy Following Surgery and Radiation in Participants With High-risk Locally Advanced Cutaneous Squamous Cell Carcinoma (LA cSCC) (KEYNOTE-630)

• Has histologically confirmed cutaneous squamous cell carcinoma (cSCC) as the primary site of malignancy (metastatic skin involvement from another primary cancer or from an unknown primary cancer is not permitted)
• Has histologically confirmed LA cSCC with ≥1 high-risk feature(s) as the primary site of malignancy
• Has undergone complete macroscopic resection of all known cSCC disease with or without microscopic positive margins
• Has completed adjuvant radiotherapy (RT) for LA cSCC with last dose of RT ≥4 weeks and ≤16 weeks from randomization
• Has completed at least 50 Gray (Gy) 25 fractions of adjuvant RT for LA cSCC prior to study entry
• Is disease free as assessed by the investigator with complete radiographic staging assessment ≤28 days from randomization
• Has provided an archival or newly-obtained tumor tissue sample adequate for Programmed Cell Death Ligand 1 (PD-L1) testing as determined by central laboratory testing
• ECOG PS 0-1
• No other histologic type of skin cancer other than invasive cSCC (eg, basal cell carcinoma) that has not been definitively treated with surgery or radiation, Merkel cell carcinoma; or melanoma
• No prior immunotherapy
• Must have recovered from all radiation-related toxicities; must have not required corticosteroids; and has not had radiation pneumonitis
• No active autoimmune disease that has required systemic treatment in past 2 years (ie, with use of disease modifying agents, corticosteroids or immunosuppressive drugs)
• No known HIV/HBV/HCV

• Primary- RFS
• Secondary- OS, QoL, Safety