Dr Rischin on the Efficacy of Adjuvant Cemiplimab in High-Risk CSCC

"We showed a marked [DFS] improvement with cemiplimab compared with placebo."

Danny Rischin, MD, a professor and director of Medical Oncology at the Peter MacCallum Cancer Centre, discussed key efficacy findings from the phase 3 C-POST trial (NCT03969004) investigating adjuvant cemiplimab-rwlc (Libtayo) vs placebo in patients with high-risk cutaneous squamous cell carcinoma (CSCC).

C-POST is a double-blind trial evaluating the efficacy and safety of the PD-1–targeting antibody cemiplimab vs placebo in high-risk patients with CSCC who have received surgery and postoperative radiotherapy. Patients defined as high-risk met criteria such as nodal disease, T4 lesions, or perineural invasion. The primary end point was disease-free survival (DFS).

Rischin reported that cemiplimab is the only systemic therapy to demonstrate a statistically significant and clinically meaningful reduction in disease recurrence in the adjuvant setting. The study demonstrated a marked improvement in DFS with cemiplimab (n = 205) compared with placebo (n = 204), including a 68% reduction in the risk of recurrence or death (HR, 0.32; 95% CI, 0.20-0.51; P < 0001). The median DFS was not reached in the cemiplimab arm, and was 49.4 months (range 48.5-not evaluable) in the placebo arm. The 2-year DFS rate was 87.1% in the cemiplimab arm vs 64.1% in the placebo arm. 

The benefit of adjuvant cemiplimab was observed across all prespecified subgroups examined. This included patients regardless of age (younger than 65 years of age, HR, 0.40, 95% CI, 0.17-0.92; at least 65 years of age, HR, 0.30, 95% CI, 0.17-0.53) and high-risk category (nodal disease, HR, 0.36, 95% CI, 0.19-0.67; non-nodal disease, HR, 0.27, 95% CI, 0.13-0.56). The improvement in DFS was attributed to reductions in both locoregional and distant recurrence. Freedom from locoregional recurrence showed an 80% reduction (HR, 0.20; 95% CI, 0.09-0.40), whereas freedom from distant recurrence showed a 65% reduction (HR, 0.35; 95% CI, 0.17-0.72). Similar efficacy was observed across cemiplimab dosing schedules.

Safety data showed that the profile of cemiplimab in the adjuvant setting was consistent with its known profile. Any-grade treatment-emergent adverse effects (TEAEs) occurred in 91% of patients in the cemiplimab group vs 89% of those in the placebo group. Grade 3 or higher TEAEs occurred in 24% of patients in the cemiplimab group vs 14% of those in the placebo group. Immune-mediated AEs were reported in 23% of patients who received cemiplimab vs 6% of those who received placebo. Rischin concluded that adjuvant cemiplimab represents a potential new standard of care for patients at high risk of CSCC recurrence.