Radiation therapy to the pelvis is recommended for patients with rectal cancer because it reduces the 20–25% probability of regional recurrences following complete surgical resection of stage II or III tumors, especially if they have penetrated through the serosa. This alarmingly high rate of local disease recurrence is believed to be due to the fact that the contained anatomic space within the pelvis limits the extent of the resection and because the rich lymphatic network of the pelvic side wall immediately adjacent to the rectum facilitates the early spread of malignant cells into surgically inaccessible tissue. The use of. | Chapter 087. Gastrointestinal Tract Cancer Part 13 Radiation therapy to the pelvis is recommended for patients with rectal cancer because it reduces the 20-25 probability of regional recurrences following complete surgical resection of stage II or III tumors especially if they have penetrated through the serosa. This alarmingly high rate of local disease recurrence is believed to be due to the fact that the contained anatomic space within the pelvis limits the extent of the resection and because the rich lymphatic network of the pelvic side wall immediately adjacent to the rectum facilitates the early spread of malignant cells into surgically inaccessible tissue. The use of sharp rather than blunt dissection of rectal cancers total mesorectal excision appears to reduce the likelihood of local disease recurrence to 10 . Radiation therapy either pre- or postoperatively reduces the likelihood of pelvic recurrences but does not appear to prolong survival. Preoperative radiotherapy is indicated for patients with large potentially unresectable rectal cancers such lesions may shrink enough to permit subsequent surgical removal. Radiation therapy is not effective in the primary treatment of colon cancer. Systemic therapy for patients with colorectal cancer has become more effective. 5-FU remains the backbone of treatment for this disease. Partial responses are obtained in 15-20 of patients. The probability of tumor response appears to be somewhat greater for patients with liver metastases when chemotherapy is infused directly into the hepatic artery but intraarterial treatment is costly and toxic and does not appear to appreciably prolong survival. The concomitant administration of folinic acid leucovorin improves the efficacy of 5-FU in patients with advanced colorectal cancer presumably by enhancing the binding of 5-FU to its target enzyme thymidylate synthase. A threefold improvement in the partial response rate is noted when folinic acid is combined with 5-FU however .
