Cancer stages refer to the type of cancer a person has, the size of the initial tumor, and whether or not the cancer has spread to other areas of the body.

Cancer staging can vary between types of cancer. However, there are staging systems that doctors frequently use to measure, describe, and treat a wide variety of cancers.

This article will examine what cancer stages mean and what the differences are between stages. It will also look at cancer grades and whether or not a cancer stage can change after diagnosis.

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Doctors use cancer stages to describe the cancer in terms of size and whether or not it has spread. According to the National Cancer Institute, cancer staging can help a doctor:

  • plan the best treatment for the person
  • recognize the severity and survivability of the cancer
  • help find clinical trials that may help with treatment

The American Cancer Society elaborate on the importance of staging for treatment. An early stage of cancer may respond well to radiation therapy or surgery, while a later stage of cancer may respond better to chemotherapy, targeted drug therapy, or immunotherapy.

Many healthcare professionals use a simple series of five different stages to describe most cancers. As the number increases, the severity of the cancer also increases, and the survival rates decrease.

Once a doctor has made a cancer diagnosis, they will use several methods to classify and stage the cancer.

Healthcare professionals refer to the cancer by the initial stage given at diagnosis, even if it changes over time. Using the cancer stage at diagnosis is a starting point for understanding how well it will respond to treatment, as well as the overall survivability rate.

In addition to the numbered stages outlined below, healthcare professionals may also describe a cancer with one of the following terms:

  • in situ, if abnormal cells are present but have not spread
  • localized, if cancer is present but only in the place where it first appeared
  • regional, if the cancer has spread to nearby tissue, organs, or lymph nodes
  • distant, if the cancer has spread to distant parts of the body
  • unknown, if a healthcare professional does not have enough information to fully classify the cancer

Additionally, not all cancers have stages. For example, doctors do not stage leukemia since it is a cancer of the blood. Some cancers, such as brain cancer, have their own system of diagnosis.

Stage 0 cancer refers to when a doctor has found abnormal tissue that has not yet spread to other areas of the body. According to the National Cancer Institute, doctors often refer to this stage as carcinoma in situ.

The diagnosis of stage 0 cancer will vary based on where and how a doctor detects it.

At this point, the abnormal cells are not actually cancer, but they may become cancer if a person does not receive treatment.

Treatment

Treatment will vary, but it generally requires the removal of the cells and surrounding tissue. More targeted treatments may not be necessary.

Outlook

The survivability of stage 0 cancers is high but will vary between cancers. For example, stage 0 breast cancer has a 99% survival rate after 5 years.

Learn more about stage 0 cancer here.

Stage 1 is an early stage of cancer. The tumor is typically small and has not spread to nearby tissue or lymph nodes.

Treatment

Treatment for stage 1 cancers often involves surgical removal or radiation therapy to remove the cancerous cells. The exact treatment method will vary based on the type of cancer a person has.

Outlook

Stage 1 cancer is an early stage of cancer and generally has a higher survival rate than more advanced stages of cancer.

Stage 2 cancer indicates that the tumor is a little larger and has grown into nearby tissue.

Diagnosis will vary based on the type of cancer a person has. The cancer is still localized, but it may have spread to nearby tissue or lymph nodes.

Treatment

Treatment can vary based on the type of cancer a person has, as well as other factors, such as their age and overall health. Treatment may involve radiation therapy or surgery to remove the tumor.

Outlook

The exact outlook for a person with stage 2 cancer will vary based on their age, overall health, and the type of cancer they have. Stage 2 cancer is often treatable and has a high survivability rate.

In stage 3 cancer, the tumor is still localized, but it is often larger than stages 1 or 2 and has invaded nearby tissue. It may also affect nearby lymph nodes.

The exact criteria of diagnosis will vary based on the type of cancer a person has.

Treatment

Treatment may be more aggressive than for stages 1 or 2. Treatments will also vary based on the location of the cancer.

Outlook

Stage 3 cancer has a generally lower survivability rate than cancers that doctors diagnose in stages 1 or 2. A person’s overall health, age, and other factors can contribute to their overall chance of survival.

Stage 4 is the most severe stage of cancer. When a doctor diagnoses stage 4 cancer, the tumor is generally very large, and the cancer has spread to other areas of the body.

Treatment

A doctor will often recommend a more aggressive treatment plan for people with stage 4 cancer. The aim of treatment is to slow or stop the spread of the cancer and to help a person feel as comfortable as possible.

The treatment plan and recommendations will vary based on the type of cancer a person has and what is most effective against it. Options may include radiation therapy, chemotherapy, targeted therapy, and surgery.

Outlook

Stage 4 cancer has a generally less favorable outlook than the other stages of cancer. A person’s age, type of cancer, and overall health all factor into how likely they are to survive.

Learn more about stage 4 cancer here.

The TNM stages make up the most common cancer staging system across the world.

The American Joint Committee on Cancer and the International Union Against Cancer developed the system to describe most types of cancer in detail.

The TNM stages work as follows.

The T measures and describes the primary tumor. Scores include the following:

  • TX​: The doctor cannot evaluate the primary tumor.​
  • T0: There is no evidence of the primary tumor​.
  • T1–T4​: These describe the size, extent, or both of the primary tumor, with larger numbers indicating a bigger tumor.

The N describes whether or not the cancer has reached nearby lymph nodes. The N can be one of the following:

  • NX: The doctor cannot evaluate the regional lymph nodes.
  • N0: The cancer has not spread to any lymph nodes.
  • N1–N3:​ The cancer has spread to regional lymph nodes, with each number describing the amount of lymph nodes affected and the extent of the spread.

The M describes whether or not the cancer has spread to other areas of the body. Possible scores include M0, in which the cancer has not spread to distant parts of the body, and M1, in which the cancer has spread to distant parts of the body.

Together, the TNM scores help determine the cancer’s overall stage. In general, the higher the number following each letter, the worse the outlook and more involved the treatment will be.

Cancer grades vary between cancer types. The grading system evaluates both the tumor and the cells within the tumor.

The National Cancer Institute indicate that there are generally four grades that a tumor may belong to, ranging from 1–4. The grades describe how close to the normal cells the cancer cells actually are.

To grade a tumor, a doctor will first remove a small piece of or the entire tumor. They will then send the sample to a laboratory, where technicians will examine it and determine the exact grade of the tumor cells.

For example, a tumor with a grade of 1 or 2 has cells that are mostly normal. Grade 1 and 2 tumors are slow to grow and spread. Tumors with a grade of 3 or 4 have more abnormal cells, and they grow and spread faster.

The grading system will vary between different types of cancer. A person should ask a doctor about their tumor’s specific grade.

In general, the higher the grade, the harder the cancer will be to treat, as it will grow and spread faster than lower grade tumors.

More often than not, cancer staging does not change. Healthcare professionals will refer to a cancer by the stage they gave at initial diagnosis, even if the cancer itself changes over time. If the cancer does change, the doctor will add more information to the original stage.

On some occasions, if a cancer comes back, a doctor may update the stage with the new stage. If this occurs, they will often repeat the same tests as before, when they first diagnosed it.

They will then add the new stage to the diagnosis, but this new stage does not replace the previous one.

Cancer staging can help doctors describe the severity of the cancer to a person and help guide the most effective treatment for them. Staging describes the size of the tumor and whether or not it has spread to other areas of the body.

There are several methods that doctors use to stage cancer, but the most common is known as TNM. Healthcare professionals often simplify the results of TNM, assigning a stage from 0–4 for many types of cancer.