After a diagnosis is made, your doctor will stage the cancer.
The stage defines the location of the cancer, how much it has spread, how big it is, and how aggressive it is.
Knowing the stage of cancer is important because it typically determines your treatment options.
A cancer is referred to by the stage it’s given when you’re first diagnosed, even if it worsens to a different stage.
How Doctors Stage Cancers
Doctors use different tests to determine a cancer’s stage. These might include:
- Physical exams
- Lab work, such as blood or urine tests
- Imaging tests, such as a magnetic resonance imaging (MRI), computerized tomography (CT), or positron-emission tomography (PET) scan
These methods can show your physician where the cancer is located and how much it’s spread throughout your body.
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What Does Cancer Metastasis Mean?
Metastatic cancer means the cancer has spread from where it started to another part of your body. Whether or not a cancer has metastasized has a significant impact on how your doctor will stage the disease and what treatments they will recommend.
Metastatic cancer is typically harder to treat. But some cancers, like testicular cancer, can still be very curable even if they’ve spread to other areas of your body.
Two Types of Staging
Doctors have two ways to stage cancer:
Clinical Staging This type of staging is done based on the results of diagnostic exams, like a biopsy and imaging test.
Pathological Staging This form takes diagnostic tests into account, but it also determines the stage based on how the cancer, and biopsies performed on surrounding tissue during surgery, appear after they are removed during surgery.
Pathological staging includes the exact size of the cancer and the number of positive lymph nodes (those containing cancer) in relation to the total number of lymph nodes removed at the time of surgery. The tumor size plus the number of positive lymph nodes determines your pathological stage, which in turn determines your final treatments for cancer.
The pathological stage of a cancer might be different than the clinical stage. For example, your doctor may not detect a tumor on an imaging test but might see it clearly during surgery. In this case, your pathological stage will be more advanced than your clinical stage.
Not everyone has surgery for cancer, especially those with a stage 4 clinical diagnosis (cancer with metastasis outside of its origin site). So clinical staging is often used instead of pathological staging.
RELATED: 10 Metastatic Cancer Blogs to Read When You Feel Like No One Understands
The TNM System
Doctors commonly use the American Joint Committee on Cancer’s (AJCC’s) TNM system to stage a cancer. It’s the most widely used cancer staging approach.
This protocol uses the letters T, N, and M to label the stage of cancer. Here’s what the letters represent:
- T stands for tumor. The letter describes how large the tumor is and where it’s located in your body.
- N is for node. It explains if the tumor has spread to lymph nodes, and if so, how many.
- M is for metastasis. It’s used to tell doctors if cancer has spread to other parts of your body, and if so, where and how far.
TNM staging is commonly used along with numbers to describe your tumor. Typically, a cancer stage includes a letter followed by a number.
Stage Grouping (Numeric Staging)
The numeric cancer staging system, which is used along with the letters TNM, includes:
Stage 0 This stage describes cancer with tumors that are usually contained at their place of origin without invading the surrounding tissues. Typically, stage 0 cancers are very curable.
Stage 1 These cancers haven’t grown deeply into nearby tissues or spread to the lymph nodes or other parts of the body. They’re typically small and often referred to as “early stage” cancers. Generally, stage 1 cancers have a good outlook.
Stage 2 and 3 These cancers have grown more deeply into nearby tissues. They may have also metastasized to lymph nodes but not other parts of the body.
Stage 4 This is the most advanced stage, which describes cancer that’s spread to other parts of the body. A stage 4 cancer is often called metastatic cancer.
Related: The Stages of Lung Cancer
A and B Designation of Cancer Staging
Sometimes stages are also subdivided into the categories A and B. For instance, your doctor might say you have a stage 3A or stage 3B cancer.
These letters can offer more information about the cancer. Stage A is typically used to describe a cancer that’s less aggressive, while stage B is used to classify a more advanced cancer within a certain category. (For example, stage 2A is less aggressive than stage 2B, but stage 3A is more aggressive than stage 2B.)
Other Factors That Affect Staging
Your doctor might consider other factors when staging the cancer, such as:
Grade The grade of the cancer describes how abnormal cancer cells look under a microscope. Tumors with cells that look more like healthy cells are called “low-grade.” Those with less healthy-looking cells might be termed “poorly differentiated,” “dysplastic,” “undifferentiated,” or “high-grade.” Grade is assigned differently depending on what type of cancer you have.
Tumor Markers These are substances found at high levels in the blood, urine, or tissue of people with cancer. In some cases, tumor markers might be more accurate at predicting how well a treatment will work for a specific cancer than staging it is. For instance, men with prostate cancer might have a high level of prostate-specific antigen (PSA) in their blood, which could offer better insight about the cancer than traditional staging techniques.
Genetics Specific genes in cancer cells might help doctors determine if certain treatments will work. Researchers are working to learn more about how a person’s genes can impact their response to cancer therapy.
Cell Type The type of cell that makes up a cancer may affect a person’s treatment and outlook. For instance, esophageal cancers can be squamous cell cancers or adenocarcinomas. Each of these types is staged differently, and oftentimes treated differently.
Other Staging Systems
Because some cancers grow and spread differently, they aren’t all staged with the TNM system. For instance, other staging systems are often used for brain cancer, Hodgkin lymphoma, childhood cancers, and lymphomas.
Also, some doctors prefer to use older staging systems because they’re more familiar with them.
Understanding Cancer Staging
Staging systems are often complex. You might not understand just what all the letters and numbers mean at first. Talk to your doctor if you have any questions. A qualified healthcare professional should be able to effectively explain your cancer stage and how it impacts your prognosis.