Staging

Staging is the process of finding out how much cancer there is in the body and where it is located. It is how the doctor learns the stage of a person's cancer. Doctors use this information to plan treatment and to help predict a person's outlook (prognosis). Cancers with the same stage tend to have similar outlooks and are often treated the same way. The cancer stage is also a way for doctors to describe the extent of the cancer when they talk with each other about a person’s case.

Why is staging needed?

Doctors need to know the amount of cancer and where it is in the body to be able to choose the best possible treatment. For example, the treatment for early stage breast cancer may be surgery and radiation, while a more advanced stage of breast cancer may need to be treated with chemotherapy, too. Doctors also use the stage to help predict the course a cancer is likely to take.

What is the doctor looking for when staging cancer?

For most cancers, the stage is based on 3 main factors, T, N, and M:

• T: is based on the size of the original (primary) tumor and whether or not it has grown into nearby tissues
• N: whether or not the cancer has spread to the nearby lymph nodes
• M: whether or not the cancer has spread to distant areas of the body

Not all cancers are staged this way. Often this is because they grow and spread in a different way than most tumors. For example, leukemias (cancers of the blood) affect the blood and bone marrow throughout the body, and so are not staged based on these factors. Cancers in or around the brain are also not staged using the TNM system, since these cancers tend to spread to other parts of the brain and not to lymph nodes or other parts of the body.

How are cancers staged?

Doctors gather different types of information about a cancer to figure out its stage. Depending on where the cancer is located, the physical exam may give some clue as to the extent of the cancer. Imaging tests like x-rays, CT scans, MRIs, ultrasound, and PET scans may also provide information about how much and where cancer is in the body. Often, biopsy is needed to confirm the diagnosis of cancer, and to find out if an abnormal spot on an imaging test is really cancer spread. A biopsy involves taking out tumors or pieces of tumors and looking at them under the microscope. Samples can be removed either during surgery or during less invasive biopsy procedures. The different techniques used to remove and examine samples are described in our Surgery document.

Types of staging

All staging is done at the time of diagnosis, before any treatment is given. There are 2 major types of staging.

Clinical staging

This is an estimate of how much cancer there is based on the physical exam, imaging tests (x-rays, CT scans, etc.), and tumor biopsies. For some cancers, the results of other tests, such as blood tests, are also used in staging. The clinical stage is a key part of deciding the best treatment to use. It is also the baseline used for comparison when looking at the cancer's response to treatment.

Pathologic staging

Pathological staging (also called surgical staging) relies on information obtained during surgery. Often this is surgery to remove the cancer and nearby lymph nodes, but sometimes surgery may be done to look at how much cancer is in the body and remove tissue samples. In some cases, the pathologic stage may be different from the clinical stage (for example, if the surgery shows the cancer has spread more than it was thought to have spread before surgery). The pathological stage gives the health care team more precise information that can be used to predict treatment response and outcomes (prognosis).

Staging systems

At one time there were many different systems used to stage cancers, and sometimes different systems were used to stage the same type of cancer. But many of these systems did not give doctors very useful information.

The TNM system

The American Joint Committee on Cancer (AJCC) developed the TNM classification system as a tool for doctors to stage different types of cancer based on certain standards. It has replaced many of the older staging systems. In the TNM system, each cancer is assigned a T, N, and M category.

The T category describes the original (primary) tumor. The tumor size is usually measured in centimeters (2 and 1/2 centimeters is about 1 inch) or millimeters (10 millimeters = 1 centimeter).

• TX means the tumor can't be measured.
• T0 means there is no evidence of primary tumor (it cannot be found).
• Tis means that the cancer cells are only growing in the most superficial layer of tissue, without growing into deeper tissues. This is also known as in situ cancer or pre-cancer.
• The numbers T1, T2, T3, and T4 describe the tumor size and/or level of invasion into nearby structures. The higher the T number, the larger the tumor and/or the more it has grown into nearby tissues.

The N category describes whether or not the cancer has spread into nearby lymph nodes.

• NX means the nearby lymph nodes cannot be evaluated.
• N0 means nearby lymph nodes do not contain cancer.
• The numbers N1, N2, and N3 describe the size, location, and/or the number of lymph nodes involved. The higher the N number, the more the lymph nodes are involved.

The M category tells whether there are distant metastases (spread of cancer to other parts of body).

• MX means metastasis can't be evaluated.
• M0 means that no distant metastases were found.
• M1 means that distant metastases were found (the cancer has spread to distant organs or tissues).

Each cancer type has its own version of this classification system, so letters and numbers don't always mean the same thing for every kind of cancer. For example, for some cancers, classifications may have subcategories, such as T3a and T3b, while others may not have an N3 category.

Stage grouping

Once the values for T, N, and M have been determined, they are combined, and an overall stage is assigned. For most cancers, the stage is a Roman numeral from I to IV. Sometimes stages are subdivided as well, using letters such as A and B.

For example, a T1, N0, M0 breast cancer would mean that the primary breast tumor is less than 2 cm across (T1), does not have lymph node involvement (N0), and has not spread to distant parts of the body (M0). This would make it a stage I cancer.

Stage 0 is carcinoma in situ for most cancers. This means the cancer is at a very early stage, is only in the area where it first developed, and has not spread. Not all cancers have a stage 0. Stage I cancers are the next least advanced and often have a good prognosis (outlook for survival). As the stage number goes up the cancers are more advanced (bigger and more widespread), but in many cases they can still be treated.

Other factors that can affect the stage

For some cancers, the values for T, N, and M aren't the only things that determine the stage. Some other factors that may be taken into account include:

Grade: For most cancers, the grade is a measure of how abnormal the cancer cells look under the microscope. This is called differentiation. Grade is important because cancers with more abnormal-looking cells tend to grow and spread faster. The grade is usually assigned a number from 1 to 3 or 4. The lower the number, the more the cancer cells look like cells from normal tissue. Higher grade cancers (meaning that the cancer cells look very different from normal cells) often have a worse prognosis, and may need different treatments. Even when the grade doesn't alter the stage for a cancer, it may still affect the outlook and/or treatment.

For some types of cancer, a different grading system is used. For prostate cancer, something called a Gleason score is used to express the grade. First, a grade (a number from 1 to 5) is assigned to the 2 areas that make up most of the cancer. These numbers are added together to get the Gleason score, which can be a number from 2 to 10.

For some sarcomas, the grade is not only based on differentiation. It also takes into account how many of the cells appear to be dividing, and how much of the tumor is made up of dying tissue.

Cell type: Some types of cancer can be made up of different types of cells. Because the type of cancer cell can affect treatment and outlook, it may be a factor in staging. Cancer of the esophagus, for example, comes in 2 main cell types: squamous cell and adenocarcinoma. Cancers that are squamous cell are staged differently than those that are adenocarcinoma.

Tumor location: For some cancers, where the tumor is located affects outlook and is taken into account in staging. For cancer of the esophagus, for example, staging factors in whether the cancer is in the upper, middle, or lower third of the esophagus.

Tumor marker levels: For prostate cancer, the level of the tumor marker prostate specific antigen (PSA) is taken into account in determining stage.

Other staging systems

Staging systems other than the TNM system are often used for Hodgkin disease and other lymphomas, as well as for some childhood cancers. The International Federation of Gynecologists and Obstetricians (FIGO) has a staging system for cancers of the female reproductive organs. The TNM stages closely match the FIGO stages, which makes it fairly easy to convert stages between these 2 systems.

Other, older staging systems (such as the Dukes system for colorectal cancer) may still be used by some doctors. If your doctor uses another staging system, you may want to find out if the stage can be converted into the TNM system. This will often help if you want to read more about your cancer and its treatment, since TNM is more widely used.

A cancer's stage does not change

An important point some people have trouble understanding is that the stage of a cancer does not change over time, even if the cancer progresses. A cancer that comes back or spreads is still referred to by the stage it was given when it was first found and diagnosed, only information about the current extent of the cancer is added.

For example, if a woman were first diagnosed with stage II breast cancer and after the cancer went away with treatment it came back with spread to the bones, the cancer is still a stage II breast cancer, only with recurrent disease in the bones. If the breast cancer did not respond to treatment and spread to the bones it is called a stage II breast cancer with metastasis in the bones. In either case, the original stage does not change and it is not called a stage IV breast cancer. A stage IV breast cancer refers to a cancer that has already spread to a distant part of the body when it is first diagnosed. A person keeps the same diagnosis stage, but more information is added to the diagnosis to explain the current disease status.

This is important to understand because survival statistics and information on treatment by stage for specific cancer types refer to the stage when the cancer was first diagnosed. The survival statistics related to stage II breast cancer that has recurred in the bones may not be the same as the survival statistics for stage IV breast cancer.

At some point you may hear the term "restaging." Restaging is the term sometimes given for doing tests to find the extent of the cancer after treatment. It may be done to measure the cancer's response to treatment or to assess cancer that has come back (recurred) and will need more treatment. Often this involves the same tests that were done when the cancer was first diagnosed: exams, imaging tests, biopsies, and possibly surgery to restage the cancer. Rarely, after these tests a new stage will be assigned, written with a lower-case "r" before the new stage to note that it is different from the stage at diagnosis. The original stage at diagnosis always stays the same. While testing to see the extent of cancer is common during and after treatment, actually assigning a new stage is rarely done, although it is more common in clinical trials.

Finding out more about your type of cancer

If you are looking for details on staging or grading for a certain type of cancer, you can find this information in each of our documents on specific cancer types. You can get any of these cancer site documents on our Web site or by calling our toll-free number below.

Additional resources

More information from your American Cancer Society

The following related information may also be helpful to you. These materials may be ordered from our toll-free number, 1-800-227-2345.

A Message of Hope: Coping with Cancer in Everyday Life (also available in Spanish)

After Diagnosis: A Guide for Patients and Families (also available in Spanish)

Imaging (Radiology) Tests

Surgery (also available in Spanish)

Talking with Your Doctor (also available in Spanish)

Testing Biopsy and Cytology Specimens for Cancer

Understanding Chemotherapy (also available in Spanish)

Understanding Radiation Therapy (also available in Spanish)

National organizations and Web sites*

In addition to the American Cancer Society, other sources of patient information and support include the following:

National Cancer Institute
Toll-free number: 1-800-4-CANCER (1-800-422-6237)
Web site: www.cancer.gov

No matter who you are, we can help. Contact us anytime, day or night, for cancer-related information and support. Call us at 1-800-227-2345 or visit www.cancer.org.

References

Edge SB, Byrd DR, Compton CC, Fritz AG, Greene FL, Trotti A, eds. American Joint Committee on Cancer Staging Manual. 7th ed. New York, NY: Springer; 2010.

Yarbro CH, Frogge MH, Goodman M, Groenwald SL, eds. Cancer Nursing Principles and Practice. 5th ed. Sudbury, MA: Jones and Bartlett Publishers, Inc. 2000.