CemiplimAb-rwlc survivorship and epidemiology (CASE): Interim results from a prospective study of the safety and effectiveness of cemiplimab in patients with advanced cutaneous squamous cell carcinoma (CSCC) in a real-world setting.

9533 Background: Cemiplimab is the first PD-L1 inhibitor approved for the treatment of patients with locally advanced (la) or metastatic (m) cutaneous squamous cell carcinoma (CSCC) not amenable to curative therapy. Here, we present an analysis of cemiplimab-treated patients with advanced CSCC enrolled in the CASE study (NCT03836105). Methods: CASE is a phase IV, multicenter, prospective, noninterventional study evaluating the effectiveness and safety of cemiplimab in patients with laCSCC/mCSCC and basal cell carcinoma. Data were collected from participating US academic and community oncology centers treating patients ≥18 years of age with intravenous cemiplimab per standard of care. The protocol was reviewed and approved by an institutional review board/ethics committee at each site and patients provided informed consent for study participation. Effectiveness outcomes included investigator-assessed (both physical and radiological) ORR (CR plus partial response) and progression-free survival (PFS). Safety outcomes included treatment-related immune-related adverse events (irAEs), infusion-related reactions (IRRs), and serious adverse events (SAEs). Results: As of December 4, 2024, 254 patients (including 44 [17%] immunocompromised/immunosuppressed) across 65 centers with advanced CSCC received ≥1 dose of cemiplimab. Median duration of exposure was 35 weeks (interquartile range: 15.0, 65.9). Most patients were aged ≥65 years (82.7%), male (78.3%), and white (89.0%). Demographics and disease characteristics were similar to those from the EMPOWER-CSCC-1 trial, with the exception of patients with Eastern Cooperative Oncology Group Performance Status of 2-3, which were excluded from the trial but represented 10.7% (27/254) of our real-world study analysis set. 64.2% of patients had laCSCC and 35.8% had mCSCC. ORR, including all patients regardless of missing response data, was 111/254 (43.7%; 95% CI: 37.5, 50.0) patients. CR was reached by 40/254 (15.7%) patients. ORR in patients with at least 1 response assessment reported was 111/201 (55.2%; 95% CI: 48.1,62.2) patients, and CR was reached by 40/201 (19.9%) patients. The overall response rate of the clinical trial (52.7%) fell within the range of our response data (43.7-55.2%). Median PFS was 14.7 (95% CI: 12.5, 21.1) months, with survival at 12 months estimated at 59.5% (95% CI: 51.4, 66.7). Treatment-related irAEs occurred in 76/254 (29.9%) patients and treatment-related SAEs occurred in 19/254 (7.5%) patients; one patient reported an IRR. Conclusions: The interim results of this Phase IV study demonstrate robust effectiveness and a generally manageable safety profile of cemiplimab in patients with laCSCC/mCSCC in real-world practice that are comparable to the results of the EMPOWER-CSCC-1 trial. Clinical trial information: NCT03836105 .