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Diagnosis and Tests for Colon Cancer

Colon cancer is typically diagnosed during a colonoscopy which is performed because an individual has concerning signs or symptoms of colon cancer or as part of routine screening in individuals 45-50 or older. During a colonoscopy, abnormal areas of the colon and polyps are biopsied. The tissue obtained during the biopsy is examined by a pathologist to confirm a diagnosis of colon cancer. Genomic profiling or biomarker testing should also be performed to see if the cancer can be targeted with precision cancer medicines. When colon cancer is confirmed additional tests are required to stage or determine the extent of spread of the cancer.

Upon completion of the clinical staging evaluation, surgery is performed to remove the cancer along with part of the normal adjacent colon and determine the level of spread within the colon and abdomen. Surgery is performed through an abdominal incision or through a laparoscope. Laparoscopic surgery is less invasive and involves the insertion of surgical instruments through very small incisions in the abdomen. Patients experience faster healing times compared with traditional abdominal surgery, and their outcomes with regard to cancer recurrence and survival have been shown in some trials to be similar.1,2,3

It is important for patients to discuss the risks and benefits of the two techniques with their doctor. Laparoscopic surgery is not yet the standard of care and is best performed by a doctor experienced with the technique.

Following surgical removal of colon cancer and examination of removed tissue under a microscope, a final “pathologic” stage will be given.

Staging of Colon Cancer

In addition to colonoscopy determining the stage of the colon cancer or the extent of the spread requires a number of tests and is ultimately confirmed by surgical removal of the cancer and exploration of the abdominal cavity. The following tests may be used to look for cancer in the chest, abdomen and pelvis. A colon cancer’s stage is a key factor in determining the best treatment.2,3

  • Computed Tomography (CT) Scan: A CT scan is a technique for imaging body tissues and organs, during which X-ray transmissions are converted to detailed images, using a computer to synthesize X-ray data. A CT scan is conducted with a large machine positioned outside the body that can rotate to capture detailed images of the organs and tissues inside the body. This method is more sensitive and precise than an X-ray.
  • Magnetic Resonance Imaging (MRI): MRI uses a magnetic field rather than X-rays and can often distinguish more accurately between healthy and diseased tissue. MRI gives better pictures of tumors located near bone than CT, does not use radiation as CT does, and provides pictures from various angles that enable doctors to construct a three-dimensional image of the tumor.
  • Colonoscopy: Because 3-5% of patients with a colon cancer can already have an additional cancer in their colon, colonoscopy is routinely recommended to identify whether a second cancer is present in the colon prior to surgery. During a colonoscopy, a long flexible tube that is attached to a camera is inserted through the rectum, allowing physicians to examine the internal lining of the colon for polyps or other abnormalities. Patients are given medication to minimize discomfort. The physician may perform a biopsy in order to collect samples of suspicious tissues or cells for closer examination.
  • Ultrasound: Ultrasound is a technique that uses sound waves to differentiate tissues based on varying tissue density. Ultrasound can be used transdermally (through the skin), transrectally (using a small probe inserted into the rectum) or intraoperatively (during surgery or during colonoscopy, which is called endoscopic ultrasound). Transrectal or endoscopic ultrasound may be used in conjunction with CT or MRI scans to help with staging.

Genetic Mutations

Not all colon cancer cells are alike. They may differ from one another based on what genes have mutations. Molecular testing is performed to identify cancer causing genetic mutations or the proteins they produce. Once a genetic abnormality is identified, a precision cancer medicine can be designed to attack a specific mutation or other cancer-related change in the DNA programming of the cancer cells. Precision cancer medicine uses targeted drugs and immunotherapies engineered to directly attack the cancer cells with specific abnormalities, leaving normal cells largely unharmed.

By testing an individual’s colon cancer for specific unique biomarkers doctors can offer the most personalized treatment approach utilizing precision cancer medicines. All individuals with colon cancer should discuss the role of genomic testing for the management of their cancer with their doctor. Testing for EGFR, HER2, BRAF, NTRK, MSI-H and other genomic markers can significantly influence treatment options and outcomes.4,5,6,7,8,9,10

  • Carcinoembryonic Antigen (CEA) is a protein that may be higher in colorectal cancer patients. High levels of CEA may indicate that cancer is present, or a treatment is not working. Low levels may indicate that the body is responding to a treatment.11

OncoType DX is a test that may help determine prognosis for patients with stage II colon cancer. This test estimates the risk of cancer recurrence by evaluating the activity of certain genes in a sample of tumor tissue. Risk of recurrence can vary greatly among patients with stage II colon cancer, and adjuvant (post-surgery) therapy is not routinely recommended for all patients with stage II colon cancer but may be considered for high-risk patients.12

Treatment information concerning colon cancer is categorized and discussed by the stage and presence or absence of specific biomarkers. In order to learn more about the most recent information available concerning the treatment of colon cancer, select the appropriate stage.

Stages of Colon Cancer

Stage I: Cancer is confined to the lining of the colon.

Stage II: Cancer may penetrate the wall of the colon into the abdominal cavity or other adjacent organs but does not invade any local lymph nodes.

Stage III: Cancer invades one or more of the local lymph nodes but has not spread to other distant organs.

Stage IV: Cancer has spread to distant locations in the body, which may include the liver, lungs, bones or other sites.



1 Lynch HT, de la Chappelle A. Hereditary colorectal cancer. New England Journal of Medicine. 2003;348:919-32.

2 Mattar MC, Lough D, Pishvaian MJ, Charabaty A. Gastrointestinal Cancer Research.2011;4:53-61.

3 Chan AT, Giovannucci EL. Primary prevention of colorectal cancer. Gastroenterology. 2010;138:2029-2043.

4 Fung T, Hu FB, Fuchs C, et al. Major dietary patterns and the risk of colorectal cancer in women. Archives of Internal Medicine. 2003; 163:309-314.

5 Thygesen LC, Gronbaek M, Johansen C et al. Prospective weight change and colon cancer risk in male US health professionals. International Journal of Cancer. 2008:123:1160-5.

6 Pischon T, Lahmann PH, Boeing H et al. Body size and risk of colon and rectal cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC). Journal of the National Cancer Institute. 2006;98:921-31.

7Paskett ED, Reeves KW, Rohan TE et al. Association between cigarette smoking and colorectal cancer in the Women’s Health Initiative. Journal of the National Cancer Institute. 2007;99:1729-35.

8 The International Agency for Research on Cancer (IARC), the cancer agency of the World Health Organization, press release.

9 Howard RA, Freedman DM, Park Y, Hollenbeck A, Schatzkin A, Leitzmann MF. Physical activity, sedentary behavior, and the risk of colon and rectal cancer in the NIH-AARP Diet and Health Study. Cancer Causes and Control. 2008;19:939-53.

10 Nilsen TI, Romundstad PR, Petersen H, Gunnell D, Vatten LJ. Recreational physical activity and cancer risk in subsites of the colon (the Nord-Trondelag Health Study). Cancer Epidemiology Biomarkers & Prevention. 2008;17:183-8.

11 Friedenreich C, Norat T, Steindorf K et al. Physical activity and risk of colon and rectal cancers: the European prospective investigation into cancer and nutrition. Cancer Epidemiology Biomarkers & Prevention. 2006;15:2398-407.

12 Doyle C, Kushi LH, Byers T et al. Nutrition and physical activity during and after cancer treatment: an American Cancer Society Guide for informed choices. CA: A Cancer Journal for Clinicians. 2006;56:323-353.

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