Approximately 40,000 Americans are diagnosed with rectal cancer annually . Surgical resection is the cornerstone of curative therapy for patients with early stage, potentially resectable disease. The addition of radiation therapy (RT) and chemotherapy can enhance both local control and cure rates in patients with either transmural invasion or positive perirectal lymph nodes.
Such therapy is often administered preoperatively. While the only definitive indication for preoperative chemoradiotherapy is the presence of a T3 or T4 (table 1) rectal cancer, other relative indications include a T1/2 lesion that is clinically node-positive, a distal tumor for which tumor regression may allow successful conversion of a planned APR to a sphincter-sparing surgical procedure, or if the preoperative staging evaluation suggests the presence of mesorectal invasion. While most of these patients are technically resectable at presentation, outcomes are better with preoperative chemoradiotherapy. (See "Neoadjuvant chemoradiotherapy and radiotherapy for rectal cancer", section on 'Indications for neoadjuvant treatment'.)
Definition of locally advanced disease — Some patients with rectal cancer present with more locally advanced or recurrent but nonmetastatic disease that cannot be easily resected. The criteria for unresectability are variable and not clearly defined. Some define a locally advanced tumor as one with endorectal ultrasound evidence of a T3/4 or N1 tumor, or one that is and/or clinically bulky .
In our view, a good working definition of a locally advanced rectal tumor is one that, in the assessment of the multidisciplinary management team of surgeons, radiation and medical oncologists, radiologists, and gastroenterologists, cannot be resected without a high likelihood of leaving microscopic or gross residual disease at the local site because of tumor adherence or fixation. A locally advanced lesion can range from a tethered or marginally resectable tumor to a fixed cancer that directly invades adjacent critical structures (eg, the duodenum, pelvic side wall).
The definition of locally advanced disease also depends upon whether the assessment of resectability is made clinically or intraoperatively. In some cases, a tumor that is considered unresectable by clinical or radiographic examination may be amenable to curative resection when the patient is examined under anesthesia.