BackgroundNo standard therapies beyond first line are established for advanced squamous cell anal carcinoma (aSCAC). Earlier preliminary data suggest activity of epidermal growth factor receptor (EGFR) inhibition and programmed cell death ligand (PD-(L))1 blockade in patients with previously treated disease. Aim of this study was to explore activity and safety of avelumab with/without cetuximab in patients with aSCAC.MethodsIn this open-label, non-comparative, ‘pick the winner’, multicenter randomized phase II trial (NCT03944252), patients with aSCAC progressing after one or more lines of treatment were randomized 1:1 to the anti-PD-L1 agent avelumab alone (arm A) or combined with cetuximab (arm B). Overall response rate (ORR) was the primary endpoint. With one-sided α error set at 0.05 and power of 80%, at least 4 responses out of 27 patients per arm had to be observed to declare the study positive. Secondary endpoints were progression free survival (PFS), overall survival (OS), and safety.ResultsThirty patients per arm were enrolled. Three patients in arm A and five in arm B achieved partial response: primary endpoint was reached in combination arm. ORR was 10% (95% CI 2.1 to 26.5) and 17% (95% CI 5.6 to 34.7) in arms A and B; disease control rate was 50% (95% CI 31.3 to 68.7) in arm A and 57 (95% CI 37.4–74.5) in arm B. At a median follow-up of 26.7 months (IQR 26.5–26.9), median PFS was 2.0 months (95% CI 1.8 to 4.0) in arm A and 3.9 (95% CI 2.1 to 5.6) in arm B. Median OS was 13.9 months (95% CI 7.7 to 19.4) in arm A and 7.8 (95% CI 6.2 to 11.2) in arm B. Acceptable safety profile was observed in both arms.ConclusionsCARACAS study met its primary endpoint in arm B, documenting promising activity of dual EGFR and PD-L1 blockade in aSCAC.