Your doctor will order a series of tests that are designed to help determine the stage, or to what extent, the cancer may have spread. This information will help your doctor decide whether surgery, radiation, chemotherapy, or a combination of these treatments is appropriate for you.
Some of the tests you may need include:
Both MRI and PET scans are special x-rays that may detect the spread of cancer into the abdomen or into other internal organs such as the lungs or liver.
Blood tests may also be ordered, including an initial CEA (carcinoembryonic antigen) level test. CEA is a substance that can be produced by colon and rectal cancer cells and released into the bloodstream. The CEA level in the blood may be high for reasons other than cancer or it can be normal in a person who has cancer. It is not used to find cancer in people who have never had cancer and appear to be healthy. However, the CEA combined with other tests may provide an early warning that cancer has returned.
Finally, a rectal ultrasound is sometimes recommended for patients with rectal cancer. Rectal ultrasound has become an important tool in determining how deep a rectal cancer may have grown and whether it has spread to nearby organs or tissues. It can help your doctor decide whether chemotherapy and radiation should be given before surgery.