Diagnosis & 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 the diagnosis. 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 It is important for patients to discuss the risks and benefits of the two techniques with their doctor, as laparoscopic surgery is not yet the standard of care, but is still considered investigational.

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

Staging

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 cancer’s stage is a key factor in determining the best treatment.

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.

Precision Cancer Medicine & Personalized Colon Cancer Care

The purpose of precision cancer medicine is not to categorize or classify cancers solely by site of origin, but to define the genomic alterations in the cancers DNA that are driving that specific cancer. Cancer used to be diagnosed solely by a visual microscopic examination of tumor tissue and all patients received the same chemotherapy. Precision cancer medicine utilizes molecular diagnostic & genomic testing, including DNA sequencing, to identify cancer-driving abnormalities in a cancer’s genome. Once a genetic abnormality is identified, a specific targeted therapy 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 medicines.

Colorectal Cancer Biomarkers

Genetic Mutations

  • The RAS Genes: KRAS and NRAS: KRAS and NRAS genes play an important role in instructing colorectal cancer cells to grow and divide as part of the epidermal growth factor receptor (EGFR) process.x  If cancer has a KRAS or NRAS mutation drugs that target EGFR; erbitux® (cetuximab)2 and vectibix® (panitumumab).3 may not work effectively. “Wild type” means you do not have the mutation and the drugs may provide some benefit. All patients with advanced colon cancer should undergo RAS biomarker testing before beginning treatment.
  • BRAF: BRAF is also a gene that signals cells to divide. Patients with mutant BRAF genes generally have a poorer prognosis (chance of survival and worse side effects) but may benefit from treatment with a precision cancer medicine.xx
  • PIK3CA: While somewhat new, a growing number of clinicians are testing for mutant PIK3CA genes; particularly in patients who have early-stage colorectal cancer. There is some suggestion that aspirin use may help decrease the risk of recurrent colorectal cancer in patients with early stage disease and PIK3CA mutation.
  • Microsatellite Instability High (MSI-H) MSI-H is a DNA abnormality found in about 15% of colon cancers. It is most often found in tumors associated with genetic syndromes like Lynch syndrome but can also occur sporadically. MSI-H is what “happens” when the genes that regulate DNA function don’t work correctly. These DNA regulating genes, known as Mismatch Repair Genes (MMR), work like genetic “spell checkers.” When problems occur in these spell-checking MMR genes, it means that areas of DNA start to become unstable. A high frequency of instability is called MSI-H. Patients with MSI-H tumors may respond differently to certain treatment. It is important to test colon cancers for this trait because it can help determine if the colorectal cancer is related to an inherited family syndrome.

Carcinoembryonic Antigen (CEA) 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.

OncoType DX:  Is a test that may help guide treatment decisions 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.4 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.

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.

Learn more here: http://oncoprecision.org/

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.

Recurrent/Relapsed: Colon cancer has progressed or returned (recurred/relapsed) following initial treatment.

Next: Screening & Prevention of Colon Cancer

References


1 Kuhry E, Schwenk WF, Gaupset R, Romild U, Bonjer HJ. Kuhry E, Schwenk WF, Gaupset R, Romild U, Bonjer HJ. Cochrane Long-term results of laparoscopic colorectal cancer resection. Cochrane Database of Systematic Reviews 2008;2:CD003432. Cochrane Database of Systematic Reviews 2008;2:CD003432.

2 Karapetis CS, Khambata-Ford S, Jonker DJ et al. K-ras mutations and benefit from cetuximab in advanced colorectal cancer. New England Journal of Medicine. 2008;359:1757-65.

3 Amado RG, Wolf M, Peeters M et al. Wild-type KRAS is required for panitumumab efficacy in patients with metastatic colorectal cancer. Journal of Clinical Oncology. 2008;26:1626-1634.

4 National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology.™ Colon Cancer. V.3.2008. © National Comprehensive Cancer Network, Inc. 2008. NCCN® and NATIONAL COMPREHENSIVE CANCER NETWORK® are registered trademarks of National Comprehensive Cancer Network, Inc.