Cemiplimab (PD-1) Boosts 2-Year DFS to 87% in High-Risk Post-Surgical CSCC

Cemiplimab, an anti-PD-1 antibody, was compared to placebo in the Phase 3 C-POST trial (NCT03969004) as adjuvant therapy after surgery, with or without radiotherapy, for high-risk cutaneous squamous-cell carcinoma (cSCC) (n = 415). After a median follow-up of 24 months, cemiplimab reduced recurrence or death events by 68% (24 events vs. 65; HR 0.32, p<0.001). This led to an estimated 24-month DFS rate of 87.1% with cemiplimab, compared to 64.1% with placebo. Both locoregional (9 events vs. 40 with placebo) and distant (10 vs. 26 events) recurrences were also reduced. Grade ≥3 adverse events were more frequent with cemiplimab (23.9% vs. 14.2%), and 9.8% of patients discontinued treatment. However, DFS with cemiplimab decisively outperforms the approximately 60–70% 2-year DFS seen with observation alone, which is the current de facto standard in this setting.