Reviewed 16 October 2012
- In the absence of bowel obstruction at presentation, a complete colonoscopy to the cecum with adequate bowel preparation should be performed to identify and biopsy any suspicious intraluminal masses and to exclude any synchronous neoplastic polyps or cancers.
- Preoperative determination of tumour height is essential in determining whether neoadjuvant radiation (with or without chemotherapy) is required. In general, tumours located in the upper rectum above peritoneal reflection (usually > 12 cm from the anal verge) may not benefit from preoperative radiation, although more advanced tumours may be radiated after multidisciplinary evaluation by the radiation oncologist, surgeon, and other treating physicians. Measurement of tumour distance from the anal verge in cm should be documented. Measurements, in decreasing order of reliability are: rigid sigmoidoscopy, flexible sigmoidoscopy/colonoscopy, endorectal ultrasound (which can often overestimate height), digital rectal examination (for low lying tumours), and pelvic imaging with CT or MRI. Tumours should be assessed on digital rectal examination as palpable or not and if palpable, mobile or fixed.
- Accurate preoperative tumour staging is essential to guide preoperative therapy. Patients with stage I tumours (T1/2, N0) do not benefit from pelvic irradiation and should proceed directly to surgery. A digital rectal examination, one of endorectal ultrasound, endoscopic ultrasound or pelvic MRI (with rectal cancer protocol) are recommended to accurately assess the clinical stage and determine the extent of pelvic disease (e.g. depth of invasion, lymph node involvement, involvement of adjacent structures and proximity to mesorectum).
- Preoperative serum carcinoembryonic antigen (CEA) tumour marker is recommended to guide subsequent follow-up.
- Preoperative CT scan of the chest, abdomen and pelvis is recommended to exclude distant metastases and to provide a baseline for surveillance.
- PET scans are not recommended for staging purposes.
- In patients with unresectable disease, core biopsy of accessible primary or metastatic lesions (e.g. liver metastasis) is recommended. Consider that predictive biomarker studies for newer targeted agents require a sufficient amount of tissue; fine needle aspirates are deemed to be insufficient in this setting.
- Although the role of this technique is still under study, computed tomography colonography (CTC) may be an option for patients unable to undergo a conventional colonoscopy. CTC, also known as Virtual Colonoscopy, is a total colonic imaging tool utilizing a specialized multislice CT scanner. This relatively brief procedure does require bowel preparation and insufflation of carbon dioxide gas. The examination occurs during a single breath hold of 10 seconds or less. Although CTG is minimally invasive and has low radiation exposure, the availability of the procedure is limited. As well, the test does not permit concomitant biopsy or polyp removal.