NEO-CESQ study: Neoadjuvant plus adjuvant treatment with cemiplimab in surgically resectable, high risk stage III/IV (M0) cutaneous squamous cell carcinoma.

9576 Background: In the last years, the treatment of locally advanced and/or metastatic cutaneous squamous cell carcinoma (CSCC) has been revolutionized by the introduction of cemiplimab, an anti-PD-1 antibody, which showed a 50% overall response rate and long term benefit (1). Recently, a phase II trial of neoadjuvant cemiplimab in resectable CSCC patients (2), showed a major pathological response (MPR) rate of 63.3%. In the current multicenter, phase II trial we evaluated the efficacy of neoadjuvant plus adjuvant immune checkpoint inhibitor in patients with surgically resectable, high-risk stage III/IV (M0) CSCC. Methods: Patients with surgically resectable high-risk stage III/IV (M0) CSCC received cemiplimab at a dosage of 350 mg every 3 weeks for two cycles prior surgery and for one year after surgery. The study primary endpoint was MPR pathological complete response (pCR) or near pCR ( < 10% remaining viable tumour cells in the surgical pathology sample) per independent central pathology review. Key secondary endpoints included recurrence-free survival (RFS), overall survival (OS), safety and the analysis of predictive biomarkers. Results: From May 2021 to October 2022 twenty-three patients were enrolled in 6 centers. pCR was observed in 9 (39%) patients and near pCR in 2 (8%) patients, while pathological partial response (10-50% remaining viable tumour cells) and no pathologic response was observed in 1 patient and 11 patients, respectively. At data lock of 31 st January 2023, only one patient was discontinued due to clinical progression. Furthermore, it was observed n = 60 (57%) any adverse events (AE) and n = 29 (30%) treatment-related AE. No any G3/G4 AE were observed. Conclusions: Neoadjuvant cemiplimab induced a pathological response in 52% of stage III/IV (M0) CSCC patients with a MPR in 48%. The study is still ongoing to evaluate the impact of combined neoadjvuant and adjuvant immunotherapy on RFS and biomarkers analysis. Clinical trial information: NCT04632433 .