Random assignment of treatment will be stratified by T3 versus T4 stage. All the patients enrolled in the study will receive one cycle of study medication (mFOLFOX6 with or without aflibercept) every 14 days for six cycles, unless unacceptable toxicity or progression is detected. After this treatment, patients will receive standard chemo-radiotherapy (CT/RT) (capecitabine 825 mg/m2 twice daily combined with a total dose of 50.4 Gy in 28 days) followed by surgery, provided they have not progressed.