Cancer staging is one of the first things that happens after a cancer diagnosis. Staging gives you and your doctor an overview of what to expect and helps to determine the best treatment options. It also helps inform ongoing cancer research.
Staging involves determining tumor size and how far cancer may have spread. The specifics of staging can vary for different types of cancer.
Let’s get into more detail about the stages of cancer, how it’s determined, and what it means for you.
When you receive a diagnosis of cancer, one of the first things your doctor will talk about is staging.
Staging tells you how far the cancer may have progressed. This information is crucial in choosing the treatments that are most likely to be effective. Staging information can also help your doctor find clinical trials for which you may be eligible.
Staging helps provide a general prognosis based on others who have been at the same stage at their diagnosis. Survival rate statistics are based on stage at diagnosis. However, your individual outlook is affected by a number of other factors that your doctor will discuss with you.
In addition, cancer studies depend heavily on staging. Documenting the stage of cancer allows researchers to evaluate and compare outcomes across different populations. It also helps them develop screening and treatment guidelines for different types of cancer.
For those reasons, it’s important to document the stage at diagnosis, whether it spreads later or not. For example, if you had stage 1 breast cancer at diagnosis, it’s always referred to as stage 1 at diagnosis, even if it has spread to distant organs since your initial diagnosis.
Clinical vs. pathological stage
Your doctor may assign a clinical stage based on tests done before treatment starts. Surgery provides an opportunity to get more detailed information, such as whether cancer cells have been found in nearby lymph nodes. This can result in a pathological stage that differs from the initial clinical stage.
Most cancers are staged from 0 to 4, with the higher number representing the most advanced disease. Keep in mind that these are general stages. The specifics of progression can vary according to cancer type.
In the TNM system:
- T stands for tumor
- N for nodes
- M for metastasis
The TNM system is structured as follows:
- 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.
- 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 number of nodes with cancer cells.
- M0: Cancer doesn’t appear to have spread.
- M1: Cancer has spread to distant sites.
Information from the TNM categories is then combined to get the overall stage. For example, if pancreatic cancer is T1, N0, M0, it would be stage 1.
For some types of cancer, these stages are also divided into lettered subcategories, such as stage 2B. In general, the stages represent:
- Stage 0: Precancer or cancer that hasn’t spread from where it started. This is also known as in situ.
- Stage 1: Cancer is small and hasn’t spread. It’s also known as localized.
- Stage 2: Cancer has grown or may have pushed into surrounding tissue, or local spread.
- Stage 3: Cancer is larger and may have spread regionally or into the lymph system.
- Stage 4: Cancer has spread to distant tissues or organs. This is advanced cancer.
Tumor grade can only be determined with a biopsy. It’s a description of how the cancer cells appear under a microscope. In general, cancer cells that closely resemble normal cells tend to grow and spread slowly. The more abnormal cancer cells are, the faster they grow and spread.
Tumor grades are assigned as follows:
- GX: undetermined
- G1: low grade, well-differentiated
- G2: intermediate grade, moderately differentiated
- G3: high grade, poorly differentiated
- G4: high grade, undifferentiated
Along with stage, tumor grade can help your doctor determine the best possible treatment.
Some cancers don’t have stages 0 to 4. For example, some types of leukemia may be referred to as either acute or chronic.
Most brain cancers aren’t staged because they don’t usually spread to the lymph nodes or elsewhere in the body.
At diagnosis, clinical staging may involve a variety of tests, depending on the type and location of cancer. This may include a physical examination and tests such as:
- CT scans
- PET scans
- blood tests
- prostate-specific antigen (PSA) test
If surgery is performed, this can provide additional information about tumor size and the involvement of nearby lymph nodes. This may help your doctor understand the pathological stage.
The stage at diagnosis helps your doctor decide what the next steps should be, as well as the overall treatment plan. For example, early stage cancers may need only localized treatment, such as surgery and radiation therapy.
Most cancers are staged shortly after diagnosis. Staging can mean slightly different things depending on the cancer type, but cancer is typically staged from 0 to 4. The higher the number, the more advanced the cancer is.
Cancer staging serves several purposes. Cancer studies and clinical trials help determine which treatments are most likely to help based on cancer stage at diagnosis. Colon cancer, for example, at stage 3 points to different treatment options than if it were stage 1.
Other individual factors are involved in prognosis, but cancer stage at diagnosis provides a general overview of what to expect. Be sure to talk to your oncologist about the stages of cancer and how it affects your treatment and outlook.