To plan optimum treatments for the best possible outcome for each patient, oncologists use imaging, biopsies, and other tests to determine colon cancer stages.
The colon (also known as the large intestine) is located at the end of your digestive tract. It removes water from digested food and moves the solid waste that remains in the rectum, where it is stored until you have a bowel movement. When malignant cells form in the tissues of the colon, cancer is the result.
However, not all colon cancers are alike.
So, when a person is diagnosed with cancer of the colon, an oncologist uses biopsies, imaging techniques, and other tests to find the stage of the cancer — whether the malignancy is localized to one spot, has spread into other tissues, or has metastasized to additional areas of the body.
Staging of cancer for optimum targeted therapy is important because, while cancer of the colon is highly treatable when caught early, it can be deadly. By zeroing in on cancer stages, doctors can tailor treatments to help patients have the best possible outcome.
Understanding cancer of the colon
Rectal cancer develops in the small (about five inches long) rectum, while cancer of the colon can develop in a much larger area — anywhere along the approximately five-foot length of the organ. But because the colon and the rectum both affect the large intestine, and are both part of the gastrointestinal tract, colon and rectal cancers are often combined in statistics as colorectal cancer.
Colorectal cancer is the second leading cause of death of men and women in the U.S. However, there’s good news about the disease.
The death rate from colorectal cancer has dropped for several decades due to better screening, including early detection and the removal of polyps from the colon before they become cancerous. In addition, there are better treatments for even late colon cancer stages than ever before, the American Cancer Society points out.
Colon cancer stages
Colon cancer stages are identified as stage 0 (the earliest stage) through stages I, II, III, and IV. The lower the number of the stage, the less the cancer has spread.
- Stage 0, also called carcinoma in situ, means that abnormal cells are found in the innermost layer of the colon wall, and they may become cancer and spread into normal tissue in the future, according to the National Cancer Institute (NCI).
- Stage I indicates a malignancy has formed in the innermost layer (mucosa) of the colon and has spread to the tissues next to the mucosa (the submucosa) — or to the colon wall’s muscle layer.
- Stage II occurs when the cancer has spread through the muscle layer of the colon wall to the outermost layer of the colon wall (the serosa); the disease may also have spread to other nearby organs.
- Stage III is divided into several types, depending on whether the disease has spread from the colon to lymph nodes (and how many), or spread to tissues near lymph nodes, and whether it has metastasized to nearby organs.
- Stage IV is the most serious form of the disease and indicates the cancer has metastasized to other parts of the body. The extent of the metastasis depends on whether the cancer has spread to one organ far from the colon (such as the liver, lung, ovary, or a distant lymph node) or the cancer has been found in tissue lining the wall of the abdomen.
How doctors identify colon cancer stages
Colon cancer is often first found when a biopsy of a polyp reveals malignant cells. After cancer is diagnosed, next comes the cancer staging process to document whether cancer cells have spread within the colon or traveled to other parts of the body, the NCI explains.
Tests and procedures used to determine colon cancer stages include:
Surgery. In addition to removing any tumor located in the colon, the surgeon will check to see how far it appears to have spread.
Lymph node biopsy. All or part of a lymph node is removed surgically or using ultrasound-guided fine needle aspiration, and a pathologist studies the removed material under a microscope to look for cancer cells.
CT scan (computerized tomography). To check for signs the cancer may have spread inside the body, a dye is injected to make organs and tissues show up more clearly in CT images (produced by a computer linked to an x-ray machine).
MRI (magnetic resonance imaging). A contrast medium called gadolinium is injected into the patient for a staging MRI. The substance collects around cancer cells so they show up brighter in computerized, detailed MRI pictures (created with radio waves and powerful magnets).
PET scan (positron emission tomography). PET scans use a radioactive material (a tracer) to produce images showing how tissues and organs are functioning. For colon cancer staging, a small amount of radioactive glucose (sugar) is injected. This makes any cancer cells show up brighter in PET scan images because malignant cells take up more glucose than normal cells.
Make sure you understand your colon cancer stage
Within each of the stages, except for stage 0, are several sub-categories, providing more information about an individual’s case — such as if the cancer has spread and, if so, how far.
The staging system most often used for colorectal cancer is the American Joint Committee on Cancer (AJCC) TNM system. The TNM system assigns letters and numbers to describe the tumor. However, the NCI uses a different lettering system.
Bottom line: Cancer stages can be complex and confusing for patients.
If you are diagnosed with cancer of the colon, it’s important to ask questions and make sure you understand what the stage of your disease is, what your best treatment is, and why.
While it’s true, later stages of cancer of the colon are the most serious forms of the disease, and the earlier stages have the best prognosis (chance of recovery), each person’s cancer case is unique.
The NCI notes the prognosis and treatment options depend not only on cancer stages but also on many other factors, including whether the cancer has blocked the colon, is a recurrence, and the patient’s own general health.
July 18, 2019
Janet O’Dell, RN