Cetuximab + Avelumab or Avelumab Alone for Unresectable, Locally Advanced or Metastatic Squamous Cell Anal Carcinoma (SCCAC) Progressed After at Least One Line of Systemic Treatment (CARACAS)

* The standard first line treatment in SCCAC is the association of 5-FU with cisplatin reaching a percentage of survival at 5 years of about 32% (Faivre 1999); in a recent case series of patients affected by SCCAC, the combination of 5-FU and cisplatin as first line treatment produced 34.4% objective response rate (ORR) and a 5 years survival rate of 15% (Sclafani 2017); * No standard second line treatment exists for SCCAC; * Cetuximab in association with irinotecan has demonstrated promising results in pretreated patients affected by SCCAC (Lukan 2009). In addition, it was recently tested in stage I-III SCCAC in association with cisplatin plus 5-FU and radiotherapy. Despite not reaching their pre-specified endpoints both studies reported an interesting activity in local control of disease, leading to hypothesize that cetuximab warrant further investigation in new strategies (Garg 2017, Sparano 2017); * Anti-PD1 treatments such as nivolumab and pembrolizumab showed promising activity in metastatic refractory SCCAC in terms of response rate and disease control with acceptable toxicity profiles (Morris 2017, Ott 2017); * The induction of immunogenic cell death was recently shown for cetuximab-based regimens (Pozzi 2016) and PD-L1 blockade should lead to NK cells activation enhancing cetuximab ADCC (Concha-Benavente 2015, Concha-Benavente 2016). On the basis of these considerations, the investigators designed the present randomized phase II trial of avelumab alone or avelumab plus cetuximab for previously treated unresectable locally advanced or metastatic SCCAC.