Cemiplimab in cutaneous squamous cell carcinoma: a longer follow‐up study focusing on the late toxicities

Background and Objectives: Cemiplimab was the first systemic therapy approved for advanced cutaneous squamous cell carcinoma (cSCC). Patients and Methods: We report findings from the Italian early access program cohort, comprising 134 patients treated with cemiplimab, with emphasis on late-onset toxicities and long-term clinical outcomes. Late toxicities were defined as treatment-related adverse events (TRAEs) occurring ≥ 6 months after therapy initiation. Objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), and overall survival (OS) were evaluated. Results: Median PFS was 9 months. 58 (43.3%) patients experienced progression while 76 (56.7%) maintained a response. Median OS was 21 months (range 0–32), and 67 (50%) patients died. The ORR and DCR were 58.9% and 72.4%, respectively. CR increased from 15% (20 patients) in September 2020 to 19.4% (26 patients) in early 2022. 15 (11.2%) patients had at least one TRAE and 2 of them stopped cemiplimab. Median time to TRAE onset was 12 months (range 6–23); all events resolved after therapy discontinuation, and none of the AEs became chronic. Conclusions: With a longer follow-up than that reported in registrational studies and real-world reports, the clinical activity of cemiplimab was confirmed, with a limited incidence of late toxicities. However, some TRAEs may emerge after prolonged treatment.