Treatment Option Overview
Primary Surgical Therapy
The primary treatment for patients with rectal cancer is surgical resection of the primary tumor. Local excision of clinical T1 tumors is an acceptable surgical technique for appropriately selected patients. For all but T1 tumors, a mesorectal excision is the treatment of choice. Very selected patients with T2 tumors may be candidates for local excision. Local failure rates in the range of 4% to 8% following rectal resection with appropriate mesorectal excision (total mesorectal excision [TME] for low/middle rectal tumors and mesorectal excision at least 5 cm below the tumor for high rectal tumors) have been reported.[1,2,3,4,5]
The low incidence of local relapse following meticulous mesorectal excision has led some investigators to question the routine use of adjuvant radiation therapy. Because of an increased tendency for first failure in locoregional sites only, the impact of perioperative radiation therapy is greater in rectal cancer than in colon cancer.
Preoperative Chemoradiation Therapy
Preoperative chemoradiation therapy has become the standard of care for patients with clinically staged T3–T4 or node-positive disease, based on the results of several studies.
German Rectal Cancer Study Group
Multiple phase II studies of preoperative chemoradiation suggested that administering radiation therapy prior to surgery improved the toxicity profile of chemoradiation and enhanced the possibility of sphincter-sparing surgery. The German Rectal Cancer Study Group randomly assigned 823 patients with ultrasound (US)-staged T3–T4 or node-positive rectal cancer to either preoperative chemoradiation therapy or postoperative chemoradiation therapy (50.4 Gy in 28 daily fractions to the tumor and pelvic lymph nodes concurrent with infusional 5-fluorouracil (5-FU) 1,000 mg/m2 daily for 5 days during the first and fifth weeks of radiation therapy). All patients received a TME and an additional four cycles of 5-FU–based chemotherapy postoperatively.
The overall 5-year survival rates were 76% and 74% for preoperative and postoperative chemoradiation, respectively (P = .80). The 5-year cumulative incidence of local relapse was 6% for patients assigned to preoperative chemoradiation and 13% in the postoperative treatment group (P = .006). Grade 3 or grade 4 acute toxic effects occurred in 27% of the patients in the preoperative treatment group as compared with 40% of the patients in the postoperative treatment group (P = .001); the corresponding rates of long-term toxic effects were 14% and 24%, respectively (P = .01).[Level of evidence: 1iA] There was no difference in the number of patients receiving an abdominoperineal resection in each arm. However, among the 194 patients with tumors that were determined by the surgeon before randomization to require an abdominoperineal excision, a statistically significant increase in sphincter preservation was achieved among patients who received preoperative chemoradiation (P = .004).