Rectal Cancer: Preoperative Evaluation and Staging
Preoperative staging of the patient with rectal cancer can provide valuable information to guide the selection of treatment options. The modalities used for preoperative staging include CT, ERUS, MR, and PET, each with its own advantages and disadvantages
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Key Concepts • Accurate preoperative staging of patients with rectal cancer helps identify patients at risk for local or distant metastasis and guides treatment decisions. • Endorectal ultrasound (ERUS) is effective for staging the depth of invasion (T stage), especially for early-stage rectal tumors (uT0, uT1) that may be considered for local excision. • Magnetic resonance (MR) has the ability to delineate the extent of locally advanced tumors and estimate the involvement of the mesorectal fascia. • ERUS and MR use surrogate markers to estimate nodal involvement—size and node morphology—and are not particularly accurate in predicting nodal metastatic spread unless there are multiple large nodes in the mesorectum. • The potential for understaging and overstaging of patients should be realized and taken into account when making treatment decisions. • High-resolution computed tomography (CT) can detect distant metastatic lesions greater than 1 cm in diameter. • Positron emission tomography (PET) scan is the most accurate assessment of total body tumor burden, especially when combined with CT (PET-CT). • PET-CT is indicated when there are equivocal findings on CT and finding distant metastatic disease would alter therapeutic decisions.
Introduction Careful pretreatment evaluation of the patient with rectal cancer is paramount for the successful management of their disease. By identifying the location of the tumor and its stage at the time of presentation, the surgeon is best prepared to discuss treatment options and prognosis with the patient and his or her family. As such, all healthcare providers caring for patients with rectal cancer should have a thorough understanding of the evaluation and staging of this disease.
Preoperative staging is performed according to the TNM classification of malignant tumors, estimating the depth of invasion into the rectal wall (cT), the presence or absence of lymph node metastasis (cN), and the presence of distant metastasis (cM). Also of importance is the determination of invasion of the anal sphincter and pelvic floor musculature, adjacent pelvic organs, or pelvic sidewall, all with significant consequences of planning and treatment to the patient. The prefix “c” is used to indicate clinical staging, which is the estimate of stage based on physical examination and radiographic studies. Unfortunately, there is often confusion regarding this distinction, with some authors describing treatment recommendations for “T3N0” tumors as determined by pretreatment staging, when instead they should describe the tumor as “cT3N0.” The difference at first glance appears trivial but can have significant consequences if the clinician fails to understand that estimates of tumor stage are just that, estimates, and that treatment planning must take into account the potential inaccuracy of these estimates. For example, understaging of the cancer preoperatively may result in the omission of preoperative radiotherapy/chemoradiotherapy and lead to an increased risk of local recurrence. Conversely, overs
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