1140P Cemiplimab Versus Historical Systemic Treatments for Locally Advanced (la) or Metastatic (m) Cutaneous Squamous Cell Carcinomas (CSCC): Results from the French Study TOSCA

The anti-PD1 antibody cemiplimab, is approved and recommended for patients with la/mCSCC based on a non-comparative pivotal study. In the absence of any prospective comparative study and to evaluate the extent of the benefit of cemiplimab versus previous therapies, the TOSCA study evaluated the effectiveness and safety of cemiplimab versus Historical Systemic Therapies (HST). TOSCA is a large French retrospective, multicenter study in patients with laCSCC ineligible for curative surgery or radiation, or mCSCC, treated with cemiplimab via the Early Access Program (EAP) in 2018-2019, or with HST in 2013-2018 (NCT05302297). Primary endpoint was OS. Secondary endpoints were PFS, DOR, ORR, and safety. Only immunocompetent patients meeting the strict indication of the EAP were considered for effectiveness analysis using inverse probability weighting method (IPW). All patients were considered for safety analysis. A total of 280 patients were included in the study (cemiplimab, n=147 and HST, n=133) and 199 patients were considered for effectiveness analysis (cemiplimab, n=129 and HST, n=70). The median age was 81 (range 48–99) and 78 (52–93) years; males were 70% and 73% for cemiplimab and HST arms, respectively. 60% and 73% of patients had mCSCC, and 50% and 31% of patients received at least one previous systemic therapy in cemiplimab and HST arms. With a median follow-up of 20 and 10 months for cemiplimab and HST arms, and after controlling for confounding using IPW, the median OS was 21 and 10 months (hazard ratio [HR] [95%CI]: 0.57 [0.45-0.73]; P-value <0.0001), respectively. The median PFS was 14 and 5 months (HR [95%CI]: 0.57 [0.43-0.76]; P-value = 0.0001). The median DOR was 22 and 5 months (HR [95%CI]: 0.58 [0.30-1.12]; P-value = 0.1033). The ORR was 57% in cemiplimab group and 33% in HST group (P-value <0.001) including 30% and 15% of complete response, respectively. Adverse drug reactions of all grades were documented in 27% (cemiplimab) and 33% (HST) of patients. TOSCA is the first comparative study in CSCC and showed significantly longer outcomes in patients treated with cemiplimab versus HST, confirming its benefits in patients with la/mCSCCs.