Preoperative chemoradiation therapy for low rectal cancer: impact on downstaging and sphincter-saving operations - Habr-Gama, Angelita; Perez, Rodrigo Oliva; Kiss, Desidério Roberto; Rawet, Viviane; Scavanini, Arceu; Santinho, Pedro Marcos; Nadalin, Wladimir (Hepato-Gastroenterology, 2004)