Two parallel phase-@ studies will assess the safety of preoperative SCRT ( @ fractions each of @Gy , on days @ to @ ) combined with ( a ) capecitabine alone ( increasing dose levels : @-@mg / m@/bid ) , on days @-@ , or ( b ) capecitabine as above plus VPA ( oral daily day -@ to @ , with an intra-patient titration for a target serum level of @-@ microg/ml ) followed by surgery @weeks after the end of SCRT , in low-moderate risk RC patients .