A sample size of @ patients ( @-@ / arm ) was calculated under the hypothesis that the addition of capecitabine or VPA to SCRT can improve the TRG@ rate from @ % to @ % , with one-sided alpha = @ and @ % power.Several biomarkers will be evaluated comparing normal mucosa with tumor ( TP , TS , VEGF , RAD@ , XRCC@ , Histones/proteins acetylation , HDAC isoforms ) and on blood samples ( polymorphisms of DPD , TS , XRCC@ , GSTP@ , RAD@ and XRCC@ , circulating endothelial and progenitors cells ; PBMCs-Histones/proteins acetylation ) .