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

Summary 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.