In a phase III trial (C-POST) reported at the 2025 ASCO Annual Meeting and in The New England Journal of Medicine, Rischin et al compared disease-free survival outcomes of adjuvant cemiplimab vs placebo in patients with high-risk cutaneous squamous cell carcinoma.
Study Details
In the trial, 415 patients from sites in 16 countries were randomly assigned between June 2019 and August 2024 to receive adjuvant cemiplimab at 350 mg (n = 209) or placebo (n = 206) given intravenously every 3 weeks for 12 weeks, followed by a dose increase to 700 mg given every 6 weeks for up to 36 weeks. Patients had local or regional disease after surgical resection and postoperative radiotherapy and were at high risk due to nodal or non-nodal features. The primary endpoint was disease-free survival.
Key Findings
Median follow-up was 24 months (range = 2–64 months).
Disease-free survival events occurred in 24 patients in the cemiplimab group vs 65 patients in the placebo group (hazard ratio [HR] = 0.32, 95% confidence interval [CI] = 0.20–0.51, P < .001). Rates of disease-free survival at 24 months were 87.1% (95% CI = 80.3%–91.6%) in the cemiplimab group vs 64.1% (95% CI = 55.9%–71.1%) in the placebo group.
The cemiplimab group had significantly lower risks of locoregional recurrence (9 vs 40 events, HR = 0.20, 95% CI = 0.09–0.40), with 2-year rates of freedom from locoregional recurrence of 94.6% vs 76.7%, and significantly lower risks of distant recurrence (10 vs 26 events, HR = 0.35, 95% CI = 0.17–0.72), with 2-year rates of freedom from distant recurrence of 94.3% vs 83.8%.
Grade ≥ 3 adverse events occurred in 23.9% of the cemiplimab group and 14.2% of the placebo group. Adverse events led to discontinuation of treatment in 9.8% vs 1.5% of patients. Immune-related adverse events occurred in 22.9% (grade ≥ 3 in 7.3%) vs 6.4% of patients. Death considered related to treatment occurred in one patient in the cemiplimab group (due to myositis).
The investigators concluded: “Adjuvant cemiplimab therapy led to longer disease-free survival than placebo among patients at high risk for recurrence of cutaneous squamous-cell carcinoma.”
Danny Rischin, MD, of the Department of Medical Oncology, Peter MacCallum Cancer Centre, Melbourne, Australia, is the corresponding author for the New England Journal of Medicine article.
Disclosure: The study was funded by Regeneron Pharmaceuticals and Sanofi. For full disclosures of all study authors, visit nejm.org.
