Real‐World Efficacy and Safety of Anti‐PD‐1 Antibody Therapy for Patients With Advanced Cutaneous Squamous Cell Carcinoma: A Single‐Center Retrospective Study in Japan

Anti-programmed cell death-1 (PD-1) immunotherapy has revolutionized the management of advanced cutaneous squamous cell carcinoma (cSCC). However, most clinical trials have primarily included Caucasian patients, and real-world data on anti-PD-1 therapy for Asian patients remain limited. We conducted a single-center retrospective study to evaluate the efficacy and safety of anti-PD-1 antibodies in patients with advanced cSCC in Japan. We analyzed 14 patients who received pembrolizumab or nivolumab, with a median follow-up of 12.1 months (1.4-40.8 months). Of these, 13 were male, and 10 had primary tumors in the head and neck region. Ten patients were previously untreated with systemic therapy, and seven had metastatic lesions. Tumor mutational burden (TMB) was assessed in seven, six of whom had high TMB. The overall response rate was 57.1%, with a complete response in 2 patients (14.3%) and a partial response in 6 patients (42.9%). The 1-year progression-free and overall survival rates were 56.2% (95% confidence intervals, 27.2-77.6) and 73.1% (95% confidence intervals, 39.1-91.0), respectively. Adverse events (AEs) occurred in 6 of 14 patients (42.9%), with one patient (7.1%) experiencing a grade 3 AE of arthralgia. No grade 4 or higher AEs were observed. The most common AE was adrenal insufficiency, which occurred in 3 patients (21.4%). Our real-world data suggest that anti-PD-1 therapy for Asian patients with advanced cSCC demonstrates efficacy and safety comparable to those observed in Caucasian populations.