Colorectal Cancer Stages / Staging

Staging Colorectal Cancer

Colorectal cancer staging is the process of finding out how far the cancer has grown into the wall of the intestine, if it has reached nearby structures and whether or not it has spread to the lymph nodes or distant organs. Understanding the stage of colorectal cancer is very important in helping to determine the prognosis and is a basis for selecting treatment options.

Colorectal cancer staging can be divided into two types: clinical and pathologic. The clinical stage is your doctor's best estimate of the extent of the disease. This is based on the results of physical exams, biopsies and diagnostic imaging tests. The pathologic stage uses all of the information from the clinical stage, plus the results of surgery. Because surgery is often used in the treatment of colorectal cancer, and it allows your doctor to get a firsthand impression of the extent of your disease, pathologic staging is usually used to describe the extent of the cancer.

Stages of Colorectal Cancer

The most commonly used colorectal cancer staging system is the TNM system, which has been established by the American Joint Committee on Cancer. The TNM system looks at three key factors to determine the stage of the cancer. First, it looks at how far the primary tumor has grown into the wall of the intestine, and if it has grown to nearby areas. This is represented by the T. Second, the extent of spread to nearby lymph nodes is examined. This is represented by the N. The last factor examined is whether or not the cancer has metastasized (i.e., spread) to other organs in the body. This is represented by the M. After all of these factors have been determined, the information is combined in a process called stage grouping. The stage of the colorectal cancer is then assigned a number from 0 (the least advanced) to IV (the most advanced). In some cases, colorectal cancer stages are subdivided using letters.

• Stage 0 Colorectal Cancer: Also known as carcinoma in situ or intramucosal carcinoma, this is the earliest stage of colorectal cancer. In stage 0, the cancer has not grown beyond the inner layer of the colon or rectum.
• Stage I Colorectal Cancer: The cancer has grown through the muscularis mucosa and into the submucosa, or it may also have grown into the muscularis propria. The cancer has not spread to nearby lymph nodes or distant sites.
• Stage II Colorectal Cancer: This stage is divided into three more separate categories: IIA, IIB and IIC. The difference between the categories lies in the extent to which the cancer has spread.
  • Stage IIA Colorectal Cancer: The cancer has grown into the outermost layers of the colon or rectum. It has not reached nearby organs or lymph nodes, and has not spread to distant sites.
  • Stage IIB Colorectal Cancer: The cancer has grown through all of the layers of the colon or rectum and into other nearby organs or tissues. Nearby lymph nodes and distant organs have not been affected.
•  Stage III Colorectal Cancer: Stage III is further divided into three more separate categories: IIIA, IIIB and IIIC. The difference between the categories lies in the extent to which the cancer has spread, and how many lymph nodes have been affected.
  • Stage IIIA Colorectal Cancer: The cancer has grown into the submucosa. It may have also grown into the muscularis propria. The cancer has spread to one to three lymph nodes near the site of the primary tumor, but has not spread to distant sites.
  • Stage IIIB Colorectal Cancer: The cancer has grown into the outermost layer of the colon or rectum, but has not reached nearby organs. Or, it has grown through the wall of the colon or rectum and into nearby organs or tissues. The cancer has spread to one to three lymph nodes near the primary site, but has not spread to distant organs.
  • Stage IIIC Colorectal Cancer: The cancer may or may not have grown through the wall of the colon or rectum, but has spread to four or more lymph nodes near the primary site. The cancer has not metastasized to distant sites.
• Stage IV Colorectal Cancer: The cancer has metastasized to distant sites such as the liver or lungs. The cancer may or may not have grown through the wall of the colon or rectum, and lymph nodes may or may not have been affected.

Next Topic: Colorectal Cancer Treatments