Stages of Cancer

Cancer staging is the process of determining the extent to which a cancer has developed by growing and spreading. Contemporary practice is to assign a number from 0 to IV to a cancer, with 0 being an advanced premalignant lesion and IV being a cancer that has spread to the limit of what the assessment measures.

Knowing the stage of your cancer helps your doctor understand how serious your cancer is and your chances of survival, and plan the best treatment for you.

An Indian doctor is giving an explanation of his patients' lung x-rays


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Purpose of Staging

There are several reasons for staging cancer cases. Knowing the extent of the disease assists your physician with determining the most appropriate treatment to cure or treat the disease, or relieve symptoms.

Staging is also used to indicate prognosis for an individual patient. Data from historical sources can provide an estimate of the expected survival rate for a particular cancer. Of course, histology and grade of tumor, patient demographics such as age, sex, and the efficacy of therapy all play a part in determining the patient's prognosis and quality of survival.

Staging provides a means of comparing local treatment results with national data based on common criteria for the extent of disease. Staging expedites the exchange of data and assists in the continuing research on cancer.

Even though each person is different and each cancer experience is unique, some generalizations can be made across cancer types and stages.

The Path of Cancer

Cancer staging is a way to group cases together and predict the likelihood of remission, which means no signs of cancer in the body and survival. It can also help predict if the cancer will grow, spread, or potentially recur.

Staging Groups

Most types of cancer have four stages: Stages I (1) to IV (4). Some cancers also have a stage 0 (zero).

  • Stage 0: This stage describes cancer in situ, which means “in place.” Carcinoma in situ is a group of abnormal cells that does not demonstrate invasion and therefore does not have any ability to spread.
  • Stage I: This stage is usually a small cancer or tumor that has not grown deeply into nearby tissues. It also has not spread to the lymph nodes or other parts of the body. It is often called early-stage cancer.
  • Stage II and Stage III: In general, these 2 stages indicate larger cancers or tumors that have grown more deeply into nearby tissue. They may have also spread to lymph nodes but not to other parts of the body.
  • Stage IV.: This stage means that the cancer has spread to other organs or parts of the body. It may also be called advanced or metastatic cancer.

The Surveillance, Epidemiology, and End Results (SEER) Program, maintained by the National Cancer Institute provides information on cancer statistics. The SEER database, however, does not group cancers by the above stages. Instead, it groups cancers into the following stages:

  • Localized: This means that the cancer is growing only in the primary site.
  • Regional: This means that the cancer has spread to nearby lymph nodes or tissues.
  • Distant: This means that the cancer has spread to organs or lymph nodes away from the primary tumor.
5-Year Survival Rates for Different Cancer Types and Treatment Options
Cancer Type Localized
Treatment
Survival Rate
Regional
Treatment
Survival Rate
Distant
Treatment
Survival Rate
Breast Tumor confined to breast, no cancerous lymph nodes
99%
Tumor spread to lymph nodes and/or chest wall
86%
Cancer spread to distant organs
27%
Colon  Tumor confined to colon, no cancerous lymph nodes
90%
Cancer spread to surrounding tissues and lymph nodes
71%
Cancer in one or more distant organs
14%
Lung (Non-small cell) Tumor confined to one lung, no cancerous lymph nodes
61%
Cancer spread to surrounding tissues and lymph nodes
35%
Cancer spread to distant organs
6%
Figures from National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) Program, January 2020.

Diagnosis

There are many tools used to diagnose cancer, including:

  • Physical examination: Depending on where the cancer is located, a physical exam may give some idea as to how much cancer there is.
  • Blood tests: For some cancers, the blood levels of certain substances (called tumor markers) can affect the stage of the cancer. 
  • Imaging tests: Like x-rays, CT scans, MRIs, ultrasound, and PET scans may also give information about how much and where cancer is in the body.
  • Endoscopy: This is sometimes used to look for cancer. For these exams, an endoscope, which is a thin, lighted tube (usually with a small video camera on the end) is put inside the body to look for cancer.
  • Biopsy: This is often is needed to confirm a cancer diagnosis. Biopsies might also be needed to find out if a lump felt on an exam or if something seen on an imaging test in another part of the body is really from the spread of cancer.

TNM Staging

The TNM system is the most widely used cancer staging system, which is used in conjunction with other criteria to determine the stage from 0 to IV. In the TNM system the T stands for tumor, N stands for nodes and M is for metastasis.

T (Tumor)

When trying to determine how much and where the cancer is in the body, doctors first look at the primary (main) tumor, which is where the cancer started. The tumor’s size, location, and whether it has grown into nearby areas can all be important. Doctors also check for other nearby tumors.

The T category can be assigned a letter or a number:

  • TX: Nothing is known about the primary tumor or it can’t be measured.
  • T0: The primary tumor can’t be located.
  • Tis: Cancer cells are only found in the layer of cells where they originated (in situ), without affecting deeper layers.
  • T1, T2, T3, T4: Tumor size from smaller to larger. The higher the T number, the larger the tumor and/or the more it has grown into nearby tissues.

N (Nodes)

Lymph nodes near the primary tumor are usually checked to find out if cancer has spread into them. Lymph nodes are small, bean-shaped collections of immune cells. Many types of cancer often spread to nearby lymph nodes before they reach other parts of the body.

The N category can be assigned a letter or a number:

  • NX: No information or lymph nodes are inaccessible.
  • N0: No cancer is found in nearby lymph nodes.
  • N1, N2, N3: Describes the location, size, or the number of nodes with cancer cells. The higher the N number, the greater the cancer has spread to nearby lymph nodes.

M (Metastasis)


Doctors might also look at other parts of the body to see if the cancer has spread. Cancer spread to parts of the body far from the primary tumor is known as metastasis.

The M category is assigned a number:

  • M0: This means that no distant cancer spread has been found.
  • M1: This means that the cancer has been found to have spread to distant organs or tissues.


Each cancer type has its own version of the TNM categories, so letters and numbers don’t mean the same thing for every type of cancer.

Clinical vs Pathological Staging

  • The clinical stage: This is an estimate of the extent of the cancer based on results of physical exams, imaging tests, endoscopy exams, and any biopsies that are done before treatment starts. For some cancers, the results of other tests, such as blood tests, are also used in clinical staging.
  • The pathological stage: This can only be determined if surgery to remove the cancer is the first treatment. This relies on the results of the exams and tests done before the surgery, as well as what is learned about the cancer during surgery.

Other Factors

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. Grade can be important because cancers with more abnormal-looking cells tend to grow and spread faster.
  • Tumor location: For some cancers, the main tumor’s location affects outlook and is taken into account in staging. The stage of cancer of the esophagus, for example, depends on whether the cancer starts in the upper, middle, or lower third of the esophagus.
  • Blood levels of tumor markers: For some cancers, the blood levels of certain substances (called tumor markers) can affect the stage of the cancer.
  • Age: For some types of cancer a person’s age at the time of diagnosis can affect their outlook, so it is taken into account when assigning a stage.
  • Cell type: Cancers in some parts of the body can start in different types of cells. Because the type of cancer cell can affect treatment and outlook, it can be a factor in staging.
  • Tumor genetics: The genes and mutations of a tumor influence cancer’s staging. When the body’s cells turn cancerous, their genes change rapidly, developing new characteristics.

Restaging

When cancer is staged again after the initial staging, it is sometimes referred to as restaging. Often the same tests that were done when the cancer was first diagnosed are carried out again. 

With any type of restaging, the new stage classification is added to the original stage, but it doesn’t replace it. The stage assigned at diagnosis is still the one that is most important when discussing statistics like survival rates.

Prognosis

For many types of cancer, the prognosis is often expressed as a survival rate. This is the percentage of people with a certain type and stage of cancer who are still alive a certain amount of time (usually five years) after being diagnosed.

It’s important to understand that while the stage of the cancer is important, many other factors can also affect a person’s outlook. Depending on the cancer type, other important factors might include a person’s age and overall health and how the cancer responds to treatment.

A Word From Verywell

The cancer staging process is multifaceted. Healthcare professionals work together to gather the many pieces of information that go into determining a cancer’s stage. Findings from procedures and tests such as physical examinations, imaging scans, biopsies, blood tests, and genetic testing are used to assign the stage. The stage is the most accurate snapshot of the cancer at that point in time.

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Article Sources
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  1. American Cancer Society. Cancer Staging. Updated June 18, 2020.

  2. Breastcancer.org. HER2 status. Updated September 21, 2020.

  3. National Cancer Institute. Restaging.