What is Cancer Staging?
Cancer staging is used to describe:
- The size of the primary tumor
- If lymph nodes are involved (Regional Spread)
- Whether the cancer has spread to other parts of the body
Cancer staging is important because it helps doctors understand how severe the cancer is and create an effective treatment plan. Doctors run many tests to analyze the cancer before assigning it a “stage,” which typically range from 0 to 4.
A cancer is always referred to by the stage it was given at diagnosis, even if the cancer spreads or shrinks. For example, a Stage 3 cancer will always be referred to as a Stage 3 cancer even if it changes significantly during the treatment process.
Cancer staging isn’t used to describe the cause of the cancer, but it can describe the genetic factors influencing the cancer.
How TNM Cancer Staging Works
TNM is the most commonly used cancer staging system and is used for most solid tumors. In this system, a cancer is described using a TNM stage:
T3 N1 M0
The TNM stage incorporates 3 types of measurements:
- Tumor (T): T describes the size of the originating cancer tumor (called the “primary tumor”). The number describes the size of the tumor; the higher the number, the larger the tumor. For example, a small tumor might be designated T1 while a larger tumor would be designated T4.
- Node (N): N describes whether or not the cancer has spread to nearby lymph nodes. The number describes how many nearby lymph nodes contain cancer. For example, N1 would mean that the cancer has spread to only a few lymph nodes, while N3 would mean that cancer has spread to more lymph nodes.
- Metastasis (M): M describes whether the cancer has metastasized; in other words, whether or not the cancer has spread to other parts of the body. M0 means the cancer has not spread to other parts of your body, and M1 means that it has.
Cancer Stage Grouping
Once a cancer has been given a TNM stage, it will be assigned a cancer stage. For most types of cancer, there are 4 stages used:
- Stage 0: Stage 0 is a cancer that is only present at its point of origin and hasn’t spread to other parts of the body. Also known as carcinoma in situ.The tumor is not necessarily cancerous, but it may become cancerous if left untreated (for example, a cancerous mole). In this scenario, surgery to remove the tumor may be the only treatment needed.
- Stage I: Also known as “early-stage” cancer, at this stage cancer is present, but it has not yet spread to other parts of the body or nearby lymph nodes. This includes smaller tumors (typically, T1-T2, N0, M0).
- Stage II: This stage typically includes larger tumors that have spread to nearby tissue but they have not spread to the lymph nodes (typically,T2-T4, N0, M0).
- Stage III: At this stage the cancer has spread to lymph nodes and is known as “locally advanced”, but has not spread to other parts of the body (typically,T1-T4, N1-N3, M0).
- Stage IV: This stage (also known as “advanced cancer” or “metastatic cancer”) means the cancer has spread to other parts of the body (T1-T4, N1-N3, M1).
Are There 4 or 5 Cancer Stages?
Most types of cancer are defined by one of four stages, but there are exceptions. The Wilms tumor, for example, is given 5 stages.
The cancer stage never changes after diagnosis, which helps doctors understand the progression of the cancer and the patient’s medical progress.
However, doctors can restage the cancer if it spreads or returns, noted by a small “r” in the TNM stage. For example, a restaged cancer might be described as T2 rN1 M1.
Other Factors Used in Cancer Staging
The TNM staging system is not used for all types of cancer. Alternative staging systems may be used for:
- Childhood Cancers: Childhood cancers use staging systems that are specific to that form of cancer.
- Blood Cancers: Blood cancers like leukemia, lymphoma, and multiple myeloma do not form solid tumors, so they don’t use the TNM system. Each type of blood cancer uses its own type of staging system. An example similar to the TNM staging is the Ann Arbor staging system which is used for lymphomas.
- Central Nervous System Tumors: Brain tumors don’t typically spread outside the brain or spinal cord..
Doctors may also include additional categories in a cancer stage, such as:
- Grades: Grade (denoted by the letter G) describes how similar the cancerous cells look to healthy cells. Cancer cells that look more similar to healthy tissues are called low-grade, while cancer cells that look very different from healthy cells are called high-grade. High-grade cancers tend to spread more quickly.
- Biomarkers: Biomarkers are substances found in the cancer that occur in unusually high levels. These may indicate how likely it is the cancer will spread quickly.
- Tumor Genetics: Doctors may do genetic testing on a tumor to try and predict whether or not the cancer will spread and which treatment methods may be most effective.
At What Stage of Cancer is Chemotherapy Done?
Chemotherapy may be done at any stage of cancer. The treatment methods recommended by your doctor will vary depending on which type of cancer you have and what your cancer stage is.
Understanding Your Cancer Prognosis
You may feel nervous or upset after receiving your cancer stage, but it’s important to remember that staging is only one of many different factors that may impact your prognosis. Your age, cancer grade, cancer location, and lifestyle choices during treatment may also impact how well your body responds to cancer treatment.
That being said, it’s always best to begin treating cancer at its earliest stages, when there’s a smaller number of cancerous cells to deal with. A cancer screening can detect cancer in its early stages, in some cases before it even causes symptoms. Speak with your doctor about getting a cancer screening if you’re at higher-risk of developing any particular type of cancer.
Unfortunately, there’s no cure for metastatic cancer, but medical researchers are constantly testing new types of treatment methods. They rely on cancer research donations to fund clinical trials and develop new medications, which is why these donations are so important.