Biopsies are usually done during the proctoscopy or colonoscopy in a doctor's office. The doctor may also perform a test called an endorectal ultrasound. This test uses sound from a probe inserted into the rectum to determine how large the tumor is, and whether it has spread. Other tests are being developed. In patients with some forms of rectal and colon cancer, abnormal genes have been found.
Genes are markers in cells associated with hereditary traits.
Tests are being developed to determine who carries these abnormal genes long before cancer appears. A doctor needs to know the stage of the disease to plan treatment. Cancer is found only in the top lining of the rectum. Cancer has spread beyond the top lining of the rectum to the second and third layers and involves the inside wall of the rectum, but has not spread to the outer wall of the rectum or outside the rectum. Stage I cancer of the rectum is sometimes called Dukes A rectal cancer.