A randomized , phase 2 trial evaluated preoperative RT ( 50.4 Gy in 1.8-Gy fractions ) with 2 concurrent chemotherapy regimens : ( 1 ) capecitabine ( 1200 mg/m ( 2 ) / d Monday-Friday ) plus irinotecan ( 50 mg/m ( 2 ) / wk 4 ) ; and ( 2 ) capecitabine ( 1650 mg/m ( 2 ) / d Monday-Friday ) plus oxaliplatin ( 50 mg/m ( 2 ) / wk 5 ) for clinical T3 or T4 rectal cancer .