The Four Stages of Colon Cancer

Colon cancer (known more formally as colorectal cancer) is the third most common cancer in the U.S. and the second leading cause of cancer deaths, according to the American Cancer Society. But, good news: It’s curable—due to an array of available treatments. The first step in deciding how to treat a cancerous polyp or mass is staging—determining if the cancer has spread, and if so, how far.


Getting a Diagnosis

The earlier colon cancer is diagnosed, the greater the chance of a cure, so it’s essential to go for regular colonoscopies, which detect polyps—abnormal growths in the colon and rectum that can become malignant. If polyps are present, they can be removed during the procedure and sent to the lab. Typically, only 1% are found to become malignant; if that happens, a pathologist will assess the tissue and assign a stage from 0 to IV (also written as 0 to 4). Basically, the lower the number, the less the cancer has spread.

intestine polyp

How Staging Is Determined

Staging is based on the TNM system, created by the American Joint Committee on Cancer, which looks at three factors.

  1. How large the original tumor (T).
  2. Whether cancer cells have spread to nearby lymph nodes (N).
  3. Whether the cancer has spread, or metastasized (M) from the colon to other parts of the body, such as the lungs or liver.
CT scan

The Challenge of Staging

Most of the time staging is straightforward. But sometimes—when doctors think there are cancerous cells in places that can’t be safely biopsied, like a lymph node near the heart or too near the intestines—the decision is based on imaging alone, which isn’t always 100% accurate, says Rishi Jain, M.D., an oncologist specializing in gastrointestinal tract cancers at the Fox Chase Cancer Center in Philadelphia. “There are challenges to accurately stage some patients. That's why I think it’s important that patients go to busy cancer centers that are trained at making these tough calls.”

endoscope polyp

Stage 0

The earliest stage is Stage 0, when abnormal cells are found in the innermost lining of the colon or rectum. Also called carcinoma in situ, these abnormal cells may become cancer and spread into nearby normal tissue. Since Stage 0 pre-cancers are typically contained in a polyp or a small part of the colon, removing the diseased area is usually all that is needed, says Andrea Cercek, M.D., a medical oncologist at Memorial Sloan Kettering Cancer Center in New York City and Stand Up to Cancer Colorectal Dream Team investigator.

large intestinal polyp

Stage I (Also Called Stage 1)

A Stage I diagnosis means cancer has spread beyond the innermost tissue but not outside the colon wall. If the cancer is part of a removed polyp, then, as with Stage 0, the removal is the treatment. But if cancer cells are at the edge of the polyp or the cancer is found to be “high grade,” which means it can spread quickly, additional surgery, known as colon resection, or colectomy, is needed, says Jeffery Nelson, M.D., surgical director of the Center for Inflammatory Bowel and Colorectal Diseases at Mercy Medical Center in Baltimore.


Stage II (Stage 2)

If you’re diagnosed with Stage II cancer, that means the cancer cells have spread beyond the colon wall or nearby tissue outside the rectum but have not gone into the lymph nodes. Colectomy surgery is the primary treatment and may be all that’s needed, says Dr. Cercek, but rectal cancer patients and certain higher-risk colon cancer cases may also be given chemotherapy.


The 3 Categories Within Stage II

Stage II colon cancer is further broken down into three categories: Stage IIA means the cancer has spread through the muscle layer of the colon wall to the outermost layer. In Stage IIB it has spread through the outermost layer but not to nearby organs. Stage IIC means there is spread of cancer cells beyond the outermost layer to nearby organs.


Stage III (Stage 3)

Patients with a Stage III diagnosis have cancer that has spread beyond the colon and/or rectum to the lymph nodes. A Stage III diagnosis will typically involve surgery followed by chemotherapy. There is good news on the chemo front, however: “Recent research has found that many stage III patients with a low risk of recurrence do just as well with only three months of chemotherapy instead of the usual six months, which is much easier to tolerate,” according to Dr. Cercek.

lymphatic system

Categories Within Stage III

As with stage II, stage III is broken further down into three categories. In Stage IIIA, the cancer has spread beyond the colon to nearby lymph nodes but not to organs or distant nodes. If the cancer has spread locally to nearby tissues or organs and is found in one to three lymph nodes, it’s Stage IIIB. If there is local spread and at least four lymph nodes are involved, the stage is IIIC.

colon surgery

Stage IV

The most serious stage is metastatic cancer, or Stage IV. Stage IVA cancers have spread to one area that’s not near the colon, such as the liver, lung, ovary or a distant lymph node. Stage IVB has spread to more than one area not near the colon, and Stage IVC has spread to the tissue lining the wall of the abdomen and possibly other areas. “We usually treat stage IV cancers with chemotherapy, then assess the response,” says Dr. Nelson. “We don’t do surgery unless the tumor is causing a life-threatening problem like perforation, bleeding, or obstruction.”

Stephanie Wood
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Stephanie Wood

Stephanie Wood is a award-winning freelance writer and former magazine editor specializing in health, nutrition, wellness, and parenting.