Irinotecan (CPT-11, Camptosar) is a semisynthetic water-soluble derivative of the plant alkaloid camptothecin. This review will focus on the potential use of irinotecan in combination with fluorouracil (5-FU) in the preoperative combined-modality treatment of advanced rectal cancer. The laboratory studies that define the mechanism of fluoropyrimidine- and camptothecin-mediated radiosensitizatio...