Therapy of Colon Carcinoma: An Oncology Perspective

Canadian Journal of Gastroenterology and Hepatology, Jul 2018

Piotr M Czaykowski, Paul C Adams

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Therapy of Colon Carcinoma: An Oncology Perspective

Can J Gastroenterol Therapy of colon carcinoma: An oncology perspective Piotr M Czaykowski MSc FRCPC 0 Paul C Adams FRCPC 0 Editor-in-Chief 0 0 Dr Piotr Czaykowski is an Assistant Professor and Medical Oncologist, Department of Medical Oncology and Haematology, CancerCare Manitoba , Winnipeg - DOncologist, Department of Medical Oncology and r Piotr Czaykowski is an Assistant Professor and Medical Haematology, CancerCare Manitoba, Winnipeg. PA: As gastroenterologists we are often the physicians that make the diagnosis of colon cancer…It seems that decisions about postoperative therapy are based on this assessment. Is this ideal at the present time? PC: There is no question that a medical oncologist’s recommendation regarding the need for systemic therapy is heavily dependent on the staging information gleaned in the initial workup. We look for the following crucial elements: Is the cancer localized? If localized, is it rectal or colon cancer? If localized, what is the status of the parameters that are linked with the risk of recurrence after surgery? If not localized, what is the extent of metastatic disease? Most commonly, the first investigation is an endoscopic evaluation of the cancer, and frequently this is performed by a gastroenterologist. This not only allows for confirmation of malignancy, but also proves crucial in helping medical and radiation oncologists determine the need for radiotherapy in distal large bowel tumours. Although the definition of where the rectum ends and the sigmoid begins remains controversial, clinical trials commonly define the rectum as being the distal 12 cm to 15 cm of the large bowel, and most of us use that as our day-to-day reference point. If I start cursing in clinic, it is usually because I have an endoscopic report that says rectal cancer (without any measurement), an operative note that calls the tumor rectosigmoid, and a computed tomography scan that calls it sigmoid. Because we only use radiotherapy routinely for rectal cancers, this question of location becomes an important one – so an explicit statement by the endoscopist of the location of the tumour is of great consequence. It is also helpful in advanced cancers to have some indication of the patency of the lumen. Even in this day and age, a surprising number of patients undergo a primary bowel resection without adequate staging. This leads to some unnecessary surprises, and occasionally leads to poor intraoperative choices. There appears to be an emerging consensus that patients with extensive metastatic disease with relatively asymptomatic primary tumours are probably best served by commencing chemotherapy as soon as possible, and worrying about the primary tumour later, if symptoms necessitate ( 1 ). Thus, the key staging investigations, often initiated by the gastroenterologist, ideally should be done before resection of the primary tumour, and should include chest imaging and a computed tomography scan of the abdomen and pelvis. A preoperative carcinoembryonic antigen test (CEA) is helpful, primarily as a prognostic indicator ( 2 ). Because I am focusing on colon cancer, I will not address the role of magnetic resonance imaging and endoscopic ultrasound in staging rectal cancer. When the patient does undergo surgery, generally for apparently localized disease, it is important that the surgeon confirm that there are no obvious metastases (and reports on this), and that he or she focuses on harvesting an adequate number of lymph nodes. It has been recognized for some time that insufficient nodal sampling leads to under-staging; the exact number of nodes necessary for accurate nodal staging remains controversial but many centres use 12 as the magic number. Clearly, finding an adequate number of nodes depends to some extent on the surgeon, but it is also heavily reliant on the pathology team. Even if positive nodes are identified, it appears to be important to remove as many as possible, because there are now some data that suggest the number and ratio of positive nodes are also important in prognosis ( 3,4 ). Currently, there are no recommendations for the routine use of positron emission tomography scanning in apparently localized colon cancer. Those centres that have ready access most commonly use this modality for trying to determine if a patient with metastatic disease can be considered for resection of the metastases with curative intent. Similarly, the use of other tumour markers (for example CA 19-9) and the use of molecular profiling (eg, looking for microsatellite instability or for overexpression of vascular endothelial growth factor or epidermal growth factor) remains the domain of clinical trials for the most part. A problem across most of Canada is that there are often excessive delays in getting the patient through the whole process of diagnosis and treatment. In a recent review of 93 Manitoba patients with stage III colon cancer who received adjuvant chemotherapy, we (...truncated)


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Piotr M Czaykowski, Paul C Adams. Therapy of Colon Carcinoma: An Oncology Perspective, Canadian Journal of Gastroenterology and Hepatology, 21, DOI: 10.1155/2007/259752