Initial Tools Used to Diagnose and Stage Colorectal Cancer
- During the physical exam, your doctor will look for tenderness, swelling, or unusual growths that might be felt in your rectum or the lower part of your colon. Your doctor will also check the rest of your body to look for signs of spread to other sites and to evaluate your overall health.
Even if the cancer was first found by sigmoidoscopy (a test that looks at the lower colon and anus), you still need a complete colonoscopy (a test that looks at the whole colon) to see if there might be more than one cancer in the colon. During a colonoscopy, biopsies of the tumor and any other suspicious tissue can be taken and evaluated under the microscope by a pathologist.
Monroe Blood Tests
A complete blood count (CBC) will help your doctor get a picture of your overall health. Many people with colorectal cancer lose blood in the stool, even if they cannot see it. The CBC will help your doctor determine how low your red blood cell count is (how anemic you are).
CEA (Carcinoembryonic Antigen)
- CEA is a substance (called a tumor marker) that can be detected in the blood. CEA is not always high in patients with colorectal cancer and it can be elevated for other reasons. For some people, CEA is a good marker that can help your doctor monitor your status during and after treatment. CEA should be measured before any treatment, including surgery.
-These are tests that look at images of different internal organs to see if the cancer has spread to other parts of the body. Imaging studies you might have for colorectal cancer include:
Chest, Abdominal and Pelvic Imaging Studies
– These are most frequently done using a CT scan (also known as a CAT Scan) but may also be done using an MRI (Magnetic Resonance Imaging) scan.
- Examination of the rectum (if you have Rectal Cancer).
PET Scans (Positron Emission Tomography)
are not routinely used to image colorectal cancer but in some cases may help locate areas of cancer activity that cannot be seen on CT or MRI scan
Tumor Tissue Testing
- Depending on your clinical situation and the recommendation of your physician, other tests may be performed on tumor tissue removed during surgery. These tests identify genetic changes that can predict your response to treatment or can indicate that your colorectal cancer is associated with an hereditary syndrome.
KRAS Mutation Analysis:
This test determines if tissue from a stage IV cancer has a mutation in the KRAS gene. In the 40% of people who have the mutation, some targeted therapies (EGFR inhibitors such as cetuximab and panitumumab) will not be effective or recommended.
Oncotype DX Colon Cancer Assay:
For patients with Stage II cancer, were the value of chemotherapy is uncertain, Oncotype DX colon cancer assay, or similar tests, may be valuable. Oncotype DX assay uses tissue from the tumor and analyzes 12 different genes to give patients a "recommended score." The score (a number between zero and 100) estimates the chance of the cancer returning after surgery. A low score means you have a low risk of recurrence, and a high score means your risk of recurrence is high.
Your final diagnosis and cancer stage may not be known until after you have surgery. During the surgery, the surgeon will remove not just the tumor itself, but also tissue around the tumor (called margins) and fat and lymph nodes attached to the area where the tumor was found. A pathologist will look at the tissue that was removed during surgery to help determine the stage of the cancer.