Treatment of patients with locally advanced and metastatic cutaneous squamous cell carcinoma (CSCC) with cemiplimab as first-line systemic therapy in Slovenia.

e21516 Background: Immunotherapy has revolutionized the treatment of advanced malignancies, including CSCC. Cemiplimab, a PD-1 immune checkpoint inhibitor, is the first PD-1 inhibitor approved for the systemic treatment of locally advanced CSCC (laCSCC) and metastatic CSCC (mCSCC) that are not curable with surgery or radiation. Objectives: The purpose of this retrospective study is to determine the efficacy and safety of cemiplimab in patients with CSCC in routine clinical practice in Slovenia. Methods: This retrospective analysis includes data from patients with laCSCC and mCSCC who were initiated on first-line cemiplimab therapy. The data collected included baseline patient characteristics (gender, age, ECOG performance status [PS], primary tumor site, site of disease dissemination, and comorbidities, including autoimmune diseases), objective response rate (ORR), progression-free survival (PFS), overall survival (OS), and safety. Results: Between May 2020 and October 2024, 37 patients started treatment. The median age of patients in this real-world cohort was 73 years (range: 48–90), and 22% had an ECOG PS of 2 or higher. Thirty patients (81%) had comorbidities, most commonly cardiovascular diseases, and 5 patients (14%) had a history of autoimmune disease. In total, 17 patients achieved a physician-assessed partial response (PR) or complete response (CR), resulting in an ORR of 45.9%. Five patients had stable disease (SD), yielding a disease control rate (DCR) of 59.5%. The median PFS was 9.3 months (95% CI, 4.1–14.5), and the median OS was 11.5 months (95% CI, 6.9–16.1), with a median duration of follow-up of 10.8 months. Nine patients (24.3%) experienced at least one immune-related adverse event (irAE), two of whom had two irAEs. All irAEs were grade 1 or 2, with only one irAE being grade 2–3. Skin toxicity was the most common irAE (73%), followed by thyroid dysfunction (27%). A higher response rate was observed in patients with irAEs, with an ORR of 56% and a DCR of 78%. Conclusions: Cemiplimab proved to be highly effective and safe in this real-world cohort of patients with laCSCC or mCSCC in Slovenia, confirming its therapeutic value in the treatment of advanced CSCC in daily clinical practice. Patients who developed irAEs had a higher response rate.