ABSTRACT

Radiation therapy (RT) has been frequently using as it has been combined to surgery for the treatment of rectal cancer for 30 years; and has been shown to be decreasing local recurrence. Preoperative RT may have some theoretical advantages including not applying radiation to the hypoxic structures, keeping the small bowel out of radiation area, decreasing possible tumor dissemination during surgery, increasing patients’ compliance and removal of the radiated bowel segment. Accordingly, its advantages regarding local recurrence and toxicity have been also shown. Long course RT (45 to 54 Gy in 5 weeks, combined with chemotherapy during the 1st and 5th weeks) and short course RT (25 Gy in 5 days) are the two preoperative RT protocols have been preferred. Swedish, Holland and MRC CR 07 trials, which have been conducted prior or after the initiation of total mesorectal excision, have revealed that short course RT may decrease local recurrence. German Trial has shown that long course chemoradiation therapy (CRT) not only decreases local recurrence but may increase the rate of sphincter preservation. It is generally accepted that long term CRT increases complete response, risk of tumor positive radial margin and sphincter preservation, but toxicity as well. As conclusion, current data support that in a patient with rectal cancer, if RT is planned to be used, it should be placed before, not after the operation. Even though there are some issues that should be discussed and investigated; one of these protocols may be better to be chosen for rectal cancer patients with T3-4 or nod positive tumors located at two third of the rectum, since they may decrease the risk of local recurrence and increase the possibility of sphincter preservation with acceptable rates of toxicity.