Cemiplimab Improves Disease-Free Survival in High-Risk Cutaneous Squamous Cell Carcinoma
Key Clinical Summary:
- Design/Population: The phase 3 C-POST trial randomized 415 patients with high-risk cutaneous squamous cell carcinoma following surgery and postoperative radiation to receive adjuvant cemiplimab or placebo. The primary end point was disease-free survival.
- Key Outcomes: Adjuvant cemiplimab significantly improved disease-free survival compared with placebo and reduced both locoregional and distant recurrence risk. Grade ≥ 3 adverse events were more frequent with cemiplimab, though patient-reported quality-of-life measures were maintained.
- Clinical Relevance: Cemiplimab is the first systemic adjuvant immunotherapy to demonstrate a clinically meaningful reduction in recurrence risk in high-risk cutaneous squamous cell carcinoma. These findings support adjuvant PD-1 blockade as a new standard consideration in this population.
Results from the phase 3 C-POST trial demonstrated that adjuvant cemiplimab significantly improved disease-free survival (DFS) compared with placebo treatment among patients with high-risk cutaneous squamous cell carcinoma (cSCC).
These results were presented by Danny Rischin, MD, Peter MacCallum Cancer Centre, Melbourne, Australia, at the 2026 Multidisciplinary Head and Neck Cancer Symposium in Palm Desert, California.
In this multicenter study, 415 patients with local and/or regional cSCC at high risk of recurrence following surgery and postoperative radiation were randomized 1:1 to receive 350 mg of cemiplimab every 3 weeks for 12 weeks followed by 700 mg every 6 weeks for up to 36 additional weeks (maximum 48 weeks total) or a placebo treatment on the same schedule. Patients were permitted to cross over upon recurrence. The primary end point was DFS. Secondary end points included freedom from locoregional recurrence, freedom from distant recurrence, overall survival (OS), and safety.
At a median follow-up of 24 months, median DFS was not reached in the cemiplimab arm and was 49.4 months in the placebo arm (hazard ratio [HR], 0.32; 95% confidence interval [CI], 0.20 to 0.51; P < .0001). The 24-month Kaplan-Meier estimated DFS was 87% and 64%, respectively. Cemiplimab improved both freedom from locoregional recurrence (HR, 0.20; 95% CI, 0.09 to 0.40) and freedom from distant recurrence (HR, 0.35; 95% CI, 0.17 to 0.72). The hazard ratio for OS was 0.78.
Grade ≥ 3 treatment-emergent adverse events were reported in 24% of patients in the cemiplimab arm and in 14% of patients in the placebo arm. Treatment-emergent adverse events led to treatment discontinuation in 10% and 2% of patients, respectively. Patient-reported outcomes demonstrated minimal changes from baseline, with similar global health status and quality-of-life scores between treatment arms. Most patients maintained or improved quality-of-life measures across treatment cycles.
“[Cemiplimab] is the first systemic adjuvant immunotherapy to demonstrate statistically significant and clinically meaningful reduction in disease recurrence for high-risk cSCC,” concluded Dr Rischin and coauthors.
“Safety profile was consistent with the known profile of [cemiplimab] in metastatic disease,” they added.
Source:
Rischin D, Chen CI, Porceddu S, et al. Clinical and patient-reported outcomes (PROs) in C-POST: Phase 3 trial of adjuvant cemiplimab (cemi) vs placebo (pbo) for high-risk cutaneous squamous cell carcinoma (cSCC). Presented at the Multidisciplinary Head and Neck Cancer Symposium. February 19 - 21, 2026. Palm Desert, California. Abstract 2079.
