Once you’ve been diagnosed with colorectal cancer, an important piece of information you’ll need right away is your cancer stage. You know those “You are here” markers on maps? Colorectal cancer staging works a lot like that.  

Cancer staging is one way to determine if, and/or how far, your cancer has spread. Your stage explains where the cancer cells have gone. 

What are the stages of colorectal cancer?

Colorectal cancer has five stages:

• Stage 0: Cancer has not grown beyond the inner layer of the colon or rectum. This is called cancer in situ.
• Stage I: Cancer has grown into the inner layers of the colon or rectum but has not spread to lymph nodes or other organs.
• Stage II: Cancer may have grown to outer layers of the colon or rectum, and/or through the wall of the colon or rectum, but it’s not spread into lymph nodes or other organs.
• Stage III: Cancer has spread into lymph nodes adjacent to where the tumor started; it has not spread to other organs.
• Stage IV: Cancer has spread into distant organ(s).

How is staging done in colorectal cancer?

There are several phases for cancer staging, the most commonly used by patients are the clinical stage and a pathological stage.

Clinical stage

Most colorectal cancer staging starts out as a clinical stage. This is determined by biopsy, labs, and imaging.

Biopsy

Many colorectal cancers are found during colonoscopy, where a biopsy is taken and sent to pathology for review. During a biopsy, cells are examined, classified, and given a grade, and this tells you what type of cancer you have and if it is likely to act aggressively.

Labs (Bloodwork)

If your colonoscopy report comes back showing you have colorectal cancer, you’ll be sent for lab work (bloodwork). Your doctor will be looking for markers like your red and white blood cell counts, and your CEA level.

Imaging

Doctors will also likely want to get a look at your abdomen, chest, and pelvis. They’ll do this through a variety of imaging scans, which may include CT scans, PET scans, and MRIs.

Pathological stage

Carmen Fong, MD, a colorectal cancer surgeon, uses the analogy of a muffin when describing clinical stage and pathological stage. An initial clinical stage is like taking a piece of the muffin off the top—you get a taste of the flavor and a general feel for the muffin. But to truly examine the muffin, you need to slice it in half. This is like pathological staging—when an entire tumor and surrounding lymph nodes (12-15 is considered an adequate sample) are removed, so they can be sliced and reviewed under a microscope.

The clinical stage is learned through the procedure, such as a colonoscopy. The pathological stage is identified through surgery.

Colon cancer pathological staging

In colon cancer, the next step after clinical staging is typically surgery. After surgery, you will receive a pathological stage, which considers lymph node status. Whether or not cancer is in the removed lymph nodes and/or adjacent organs will impact your pathological stage and the next steps for treatment.

Rectal cancer pathological staging

In rectal cancer, if you have a rectal tumor that appears to be larger or has involved the tissues surrounding the rectum, your clinical stage will lead your team to proceed with chemotherapy and/or radiation to shrink the tumor prior to surgery. A pathological stage will follow surgery after you receive initial treatment.

Why do some patients say letters after their stage, like Stage 3a?

The tumor, node, and metastasis (TNM) classification of your tumor is what’s used to determine your stage.

The AJCC’s TNM Staging System

The American Joint Committee on Cancer (AJCC) developed and continues to update the TNM system, which scores your tumor in each of these areas. The score is used to classify your cancer:

• T (tumor): How far the tumor has grown into or through the colon or rectum wall (scored from 0–4)
• N (node): Whether any lymph nodes near the original tumor have cancer (scored from 0–3)
• M (metastasis): Whether cancer has spread to areas or organs outside the colon (scored from 0-M1, M1a, M1b, and M1c)

Stage	TNM Classification
Stage 0	Tis, N0, M0
Stage I	T1 or T2, N0, M0
Stage IIA	T3, N0, M0
Stage IIB	T4a, N0, M0
Stage IIC	T4b, N0, M0
Stage IIIA	T1 or T2, N1 or N1c, M0 or T1, N2a, M0
Stage IIIB	T3 or T4a, N1 or N1c, M0 or T2 or T3, N2a, M0 or T1 or T2, N2b, M0
Stage IIIC	T4a, N2a, M0 or T3 or T4a, N2b, M0 or T4b, N1 or N2, M0
Stage IVA	Any T, Any N, M1a
Stage IVB	Any T, Any N, M1b
Stage IVC	Any T, Any N, M1c

Can a stage change?

The answer is actually somewhat complex.

The reason your medical team will assign a TNM stage is to classify your cancer and provide clarity for your treatment options. A stage helps reduce ambiguity when it comes to determining how to treat a patient, and it can help several health care professionals get on the same page when it comes to your care.

Usually, you will receive a temporary initial stage, a clinical stage, which is denoted by cTNM. This is the only staging that may be done in some cases if a patient never has surgery, and it’s determined by examinations including scans.

However, there are several time points that clinicians look at throughout the cancer continuum, and based on these time points, your stage may be updated: clinical stage (cTNM), pathological stage (pTNM), post therapy stage (ycTNM or ypTNM), recurrence (rTNM) and autopsy (aTNM).

Because many patients have surgery and get their primary tumor and surrounding tissues sent to the lab, they will receive a pathological stage (pstage (pTNM)). Rectal cancer patients who don’t receive surgery right away but undergo preoperative therapy get assigned a ycTNM.

These stages are what most patients understand and identify as their cancer stage since it indicates the extent of the disease and determines the treatment plan.

The extent of disease at or around the time of diagnosis stays with a patient forever. So, if you have cancer in the lymph nodes at the time of diagnosis and develop lung metastases, you would be said to have stage III disease with recurrence in the lungs. The stage III at diagnosis remains the stage in the databases, and it’s considered recurrent cancer.

HOWEVER: If your cancer has metastasized and you’re looking for clinical trials and planning treatment, consider yourself a stage IV patient and look for clinical trials for stage IV cancer—even if you had an earlier stage at diagnosis.

What if I’ve had two different cancers? How does that impact colorectal cancer staging?

Each cancer gets its own stage. Some patients are considered cured (or they are classified as having NED: no evidence of disease) of a cancer only to have a second cancer appear years later. (A cancer that was not a recurrence from their first cancer, but a new and separate cancer.)

In this instance, the subsequent cancer receives its own stage, which will play a role in determining treatment plans. Subsequent cancers are not necessarily stage IV cancers—sometimes these cancers are caught in early stages and patients do not need treatment outside of surgery.

The development of more than one colon cancer in the same person is especially common in patients with genetic syndromes that predispose them to the development of colorectal and other cancers.

How common is my cancer stage?

Based on data from the National Cancer Institute’s SEER program, the following are the percentages of cases by stage in the U.S.:

• Stage I-II (localized): 35% of patients
• Stage III (regional): 36% of patients
• Stage IV (distant): 23% of patients
• Unknown: 6%

Have people of every stage beat this disease?

Yes! There are survivors from every stage of colorectal cancer, and many of them have shared their stories in our Champion Stories hub to encourage you. Browse their stories and words of encouragement, and don’t forget to add your own when you’re ready.