Colorectal cancer can be identified during a routine screening. In other cases, doctors will order additional tests after discussing symptoms with a patient.
The following tests may be used to diagnose colorectal cancer or find out if it has spread. Tests also may be used to find out if surrounding tissues or organs have been damaged by treatment.
Endoscopic tests, which may include:
- Colonoscopy: A tiny camera on flexible plastic tubing (colonoscope) is inserted into the rectum and advanced through the colon. This gives the doctor a view of the entire colon. Tissue or polyps can be removed and looked at under a microscope
- Sigmoidoscopy: Similar to colonoscopy but a shorter examination of the rectum and lower colon.
Fecal DNA test (FDNA): This take-home test identifies DNA changes in the cells of a stool sample.
Fecal immunochemical test (FIT): This take-home test identifies blood proteins in stool.
Fecal occult blood test (FOBT): This take-home test identifies blood in stool.
Once diagnosed with colorectal cancer, your doctor might perform the following tests:
Blood test for carcinoembryonic antigen (CEA): CEA is a protein, or tumor marker, made by some cancerous tumors. This test also can be used to find out if the tumor is growing or has come back after treatment.
Imaging tests, which may include:
- CT or CAT (computed axial tomography) scan
- MRI (magnetic resonance imaging) scan including dedicated rectal cancer MRI
- PET/CT (positron emission tomography) scan
- Endoscopic ultrasound (EUS)
Imaging tests can help to provide detailed information about the size or location of colorectal cancer and assess if the cancer has spread to other parts of the body.
Other imaging tests
Virtual colonoscopy or CT (computed tomography) colonoscopy: A focused CT scan of your abdomen and pelvis to create 3-D images, that can show polyps and other abnormalities in your colon and rectum. This test can be used for patients with medical conditions, such as bleeding disorders, that make traditional colonoscopies riskier.
Double contrast barium enema (DCBE): Barium is a chemical that allows the bowel lining to show up on an X-ray. A barium solution is given by enema, and then a series of X-rays are taken.
If you are diagnosed with colorectal cancer, your doctor will determine the stage of the disease. Staging is a way of classifying cancer by how much disease is in the body and where it has spread when it is diagnosed. This helps the doctor plan the best way to treat the cancer. It’s important that staging be performed before treatment begins.
(Source: National Cancer Institute)
Stage 0: Abnormal cells are found in the inner lining of the colorectal tissue. These abnormal cells may become cancer and spread into nearby normal tissue. Stage 0 also is called carcinoma in situ.
Stage 1: Cancer has formed and spread into the first (submucosa) or second (muscle) layers of the bowel wall. It has not spread outside of the bowel.
Stage 2: Cancer has spread outside of the rectal walls into the surrounding fat or nearby tissue. It has not gone into the lymph nodes. It is divided into stages IIA, IIB or IIC depending on the extent of local tumor involvement.
Stage 3: Cancer has spread to nearby lymph nodes. It has not spread to other parts of the body. It is divided into stages IIIA, IIIB or IIIC depending on the extent of local tumor involvement and the number of lymph nodes that contain cancer.
Stage 4: Cancer has spread to other parts of the body, such as the liver, lungs or ovaries. It is divided into stages IVA,IVB and IVC depending on the number of different other parts of the body or location to which the cancer has spread.
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