Surgical resection is the cornerstone of curative therapy for rectal cancer. However, surgery alone provides a high cure rate only for patients with early stage disease. Following potentially curative resection, five-year survival rates are 80 to 90 percent for patients with stage I rectal cancer, while they are below 80 percent for those with stage II or III disease (table 1). (See "Approach to the long-term survivor of colorectal cancer", section on 'Prognosis and natural history'.)
Many randomized trials have attempted to improve the results of surgery alone through the addition of chemotherapy and radiation therapy (RT), both before and after surgery. RT has emerged as an important component of adjuvant therapy for rectal cancer because of the distinct patterns of failure following resection. In contrast to colon cancer, in which the failure pattern is predominantly distant metastases, the site of first failure in patients undergoing surgery for rectal cancer is equally distributed locally (ie, pelvis) and in distant sites (eg, liver, lung) .
The majority of early trials of combined modality therapy in rectal cancer evaluated postoperative RT with or without chemotherapy. More recently, focus has shifted to preoperative (neoadjuvant) application of combined chemoradiotherapy. Neoadjuvant rather than adjuvant chemoradiotherapy is preferred for patients with transmural (T3/4) (table 1) or node-positive tumors, particularly if they are low-lying within the rectum. Advantages of this approach include better local control, increased likelihood of sphincter saving surgery, and a lower risk of chronic anastomotic stricture. (See "Neoadjuvant chemoradiotherapy and radiotherapy for rectal cancer", section on 'Indications for neoadjuvant treatment'.)
Nevertheless, initial surgery is still utilized in clinical practice, especially for those patients whose preoperative local staging evaluation cannot distinguish between a cT2 or T3 tumor, and proximal cT3N0 tumors for which RT may not be recommended after a total mesorectal excision (TME). (See "Pretreatment local staging evaluation for rectal cancer" and "Neoadjuvant chemoradiotherapy and radiotherapy for rectal cancer", section on 'T1/2 and clinically node-positive' and "Neoadjuvant chemoradiotherapy and radiotherapy for rectal cancer", section on 'cT3N0 tumors' and 'Favorable risk rectal cancer' below.)
Postoperative (adjuvant) therapy for resected rectal cancer in patients who have not received neoadjuvant chemoradiotherapy will be reviewed here. Neoadjuvant treatment approaches for rectal cancer, the role of adjuvant chemotherapy in patients who have received neoadjuvant therapy, the preoperative staging evaluation, surgical management of rectal cancer, treatment of locally advanced unresectable or locally recurrent rectal cancer, and posttreatment follow-up after definitive treatment are discussed separately.