Introduction
The aims of the preoperative evaluation of a patient with rectal cancer are to assess both the patient and the tumor and offer a tailored treatment plan that optimizes both cure and sphincter preservation. Accurate staging of rectal cancer is the foundation upon which the choice of the best therapeutic strategy rests. Locoregional staging assists in selecting patients who can benefit from neoadjuvant chemoradiation treatment and in determining the extent of surgery. Early-stage rectal cancer can be treated by local excision or radical resection alone, but T3 cancers with a threatened circumferential resection margin (CRM) may be best managed by neoadjuvant chemoradiation followed by surgery. This approach, when combined with skillfully performed surgery, is associated with the lowest recurrence rates.
In this chapter we discuss our approach to preoperative evaluation of rectal cancer, including clinical assessment, endoscopic evaluation and biopsy, locoregional staging with endoscopic rectal ultrasound and/or magnetic resonance imaging (MRI), and investigation for distant metastases with computed tomography (CT) and other modalities. Finally, we discuss the role and importance of the multidisciplinary team in preoperative evaluation.
Clinical Assessment
History
A detailed cancer-specific history is an important initial step to elicit symptoms that may indicate the location and degree of disease. An asymptomatic patient may have an early, localized tumor, whereas a change in bowel habits and rectal bleeding may be symptoms of a more advanced tumor. Furthermore, tenesmus, anal pain, and incontinence are characteristics of an advanced distal lesion that is impinging on the anal sphincter. Constitutional symptoms including weight loss, anorexia, and fever may be indicators of systemic disease.
Obtaining a complete family history is important to screen for hereditary cancer syndromes and at times to refer the patient for genetic counseling. Any patient with rectal cancer who is younger than 50 years should be referred, along with patients who have at least one affected first-degree relative.
Finally, the history should elucidate prediagnosis bowel habits and fecal continence, as well as risk factors for postoperative fecal incontinence. Risk factors include previous anorectal surgery or trauma, vaginal deliveries with or without episiotomies or tears, and relevant neurologic disorders.
Physical Examination
Precise preoperative assessment of a rectal cancer by the operating surgeon through use of digital rectal examination and rigid proctosigmoidoscopy is critical. Digital rectal examination should include assessment of the distance between the lower border of the tumor and the anorectal ring, its fixation to the sphincters and to any adjacent structures (e.g., vagina, prostate, sacrum), the position of the tumor (anterior, posterior, or lateral), and the patient’s sphincter tone and integrity ( Table 28-1 ). After this examination, the surgeon can often determine whether the patient is a candidate for sphincter-saving surgery (i.e., low anterior resection or intersphincteric resection with colorectal or coloanal anastomosis) or will need an abdominoperineal resection.
| Distance from the anorectal ring |
| Position of the tumor Anterior Posterior Lateral |
| Degree of circumferential involvement |
| Mobility Mobile Tethered Fixed |
| Fixation to the sphincters |
| Fixation or invasion to adjacent structure Vagina/prostate Sacrum Pelvic side wall |
| Sphincter Resting and squeeze tone Defect |
Abdominal examination should include inspection for prior incisions and evaluation for abdominal distention when an obstruction is suspected. Furthermore, for patients in whom a stoma is anticipated, the right and/or left lower quadrant stoma site should be marked. Ideally, this marking is performed by enterostomal therapists at a site that will minimize postoperative stoma complications.
Endoscopic Evaluation and Biopsy
A complete colonoscopy should be performed for all patients who present with a nonobstructing rectal cancer because the incidence of a synchronous cancer or polyp is 1% to 3% and 20% to 30%, respectively. Patients with partial obstruction as a result of the rectal tumor may complete colonic evaluation by CT colonography or double-contrast barium enema. If a patient does not undergo complete preoperative evaluation of the colon, a colonoscopy should be performed intraoperatively after gut lavage or within 6 months of surgical treatment (the second best option).
All patients should have histologic confirmation of the rectal cancer before proceeding with a proctectomy. For patients with nondiagnostic biopsies, a repeat biopsy should be performed. Lesions amenable to local excision may be excised for histologic evaluation, upon which further treatment decisions will be made. Universal tumor testing for mismatch repair deficiency is often performed after resection, but it is better to perform this testing with a preoperative biopsy. Screening for microsatellite instability or use of immunohistochemistry to measure the level of expression of mismatch repair proteins will sometimes suggest Lynch syndrome and trigger genetic testing. The results also have implications for surveillance and testing of other organs.
Preoperative Staging with Imaging Modalities
Locoregional Evaluation
Preoperative clinical staging of the depth of tumor invasion (T staging) and the presence of mesorectal lymph node metastases (N staging) should be performed for all rectal cancers. Other important features that should be evaluated include CRM and extramural venous invasion (EMVI). CRM is defined as the shortest distance between the rectal tumor (including noncontiguous tumor) and the mesorectal fascia in the total mesorectal excision specimen. A positive CRM is defined as the presence of tumor 1 mm or less from the resection margin and is associated with significantly higher rates of local recurrence. Careful preoperative assessment of the mesorectal fascia is of prime importance because a potentially threatened CRM is an indication for neoadjuvant treatment. This strategy is used to cause tumor regression away from the CRM prior to surgery in order to maximize negative CRM. EMVI refers to extension of the rectal tumor into the vessels beyond the muscularis propria as visualized on MRI. EMVI has been shown to be an independent, negative predictor of survival.
High-resolution MRI should be used for local staging of rectal cancer, whereas endorectal ultrasound (ERUS) may be helpful in distinguishing between benign polyps and early T1 cancers. In difficult cases, especially those below the mesorectum, obtaining both an MRI and ERUS sometimes can be useful.
Tumor Stage and the Circumferential Resection Margin
ERUS provides a complete circumferential image of the rectal wall using a rigid or flexible probe with a water-filled balloon to maintain acoustic contact. Ultrasound frequency determines the resolution of the image. Two-dimensional imaging yields a five-layer image of the rectal wall composed of three hyperechoic and two hypoechoic circles ( Fig. 28-1 ). More recently, three-dimensional ERUS with coronal, sagittal, and transverse images has been used in an attempt to improve the accuracy of ultrasound imaging. However, ERUS remains an operator-dependent examination with a considerable learning curve and interobserver variability. A systematic review that assessed ERUS accuracy for 4118 rectal cancer cases reported a mean accuracy of 85% for tumor stage. However, the authors observed that accuracy rates significantly declined in recent years, which may be attributable to more recent widespread use of ERUS in low-volume centers compared with earlier years, along with an inflated accuracy in earlier studies.
ERUS may be useful for the assessment of large polyps when a possibility of invasion exists. These early cancers involving only the submucosa can usually be accurately distinguished from those that penetrate the muscularis propria or extend into the perirectal fat ( Fig. 28-2 ). ERUS accuracy varies with T stage. Many studies report better accuracy using ERUS for early compared with advanced rectal cancers. A review of 31 publications over two decades reported an overall accuracy of 82% for ERUS, with accuracies ranging from 40% to 100% for T1 and T2 tumors compared with 25% to 100% for T3 and T4 tumors. In a recent meta-analysis of 11 studies it was found that the sensitivity of ERUS in identifying T1, T2, T3, and T4 tumors was 84%, 76%, 96%, and 76%, respectively. ERUS has repeatedly been reported to overstage T2 lesions. Peritumoral inflammation and desmoplastic changes are common causes of this overstaging because both are difficult to differentiate from actual tumor borders. Finally, ERUS cannot be used to evaluate stenotic lesions because the probe cannot be safely or comfortably inserted into the rectal lumen. Upper rectal lesions can be difficult to reach with the rigid ultrasound probe because of the angulation of the sacrum.
