• The tumor penetrates through the bowel wall or encircles the rectal wall.
• The tumor is larger than 6 cm (2½ in.).
There are several conditions found at the time of diagnosis of colon cancer that suggest an unfavorable outcome:
• Pelvic nodes (rectal) or abdominal nodes (colon) are involved.
• There is a large bowel or rectal obstruction.
• The veins or lymphatic vessels of the bowel have been invaded.
• The tumor cells are poorly differentiated under the microscope.
• The chromosome pattern is abnormal.
• The level of carcinoembryonic antigen (CEA) in the blood is high before surgery.
• The cancer cell DNA is abnormal (investigational).
Caution is needed when planning treatment for rectal cancers because the rectum lacks the covering layer of the bowel (the serosa). Thus, treatment of these tumors differs.
