Anti-PD-1 and mDCF Followed by Chemoradiotherapy in Patients With Stage III Squamous Cell Anal Carcinoma.

"A total of 9 EDTA (ethylenediaminetetraacetic acid) tubes will be collected at each time point to perform:~PBMC collection: 6 EDTA tubes of 6 ml of peripheral blood mononuclear cell \[PBMC\] will be sent to the central laboratory (Biomonitoring Platform of Besançon, CHRU de Besançon located at Etablissement Français du Sang) at room temperature within 24 hours via an approved carrier for their processing, storage and immunomonitoring analysis. A sending sheet of the samples will be attached to each single sample.~Plasma collection: One 6 ml EDTA tube should be frozen in each investigation center for plasma collection.~Plasma for circulating tumoral DNA (ctDNA) collection: Two 4 ml EDTA tube should be frozen in each investigation center for ctDNA collection."

A tumor biopsy will be performed at 2 months after enrollment.