Cancer staging is the process of determining the extent to which a cancer has grown and spread. It’s normally performed at cancer diagnosis before any cancer treatment is given.
The stage of a cancer provides information on the size of the cancer or primary tumor and whether it has spread from its original site — for example, if the cancer has spread to surrounding tissue, nearby lymph nodes, or distant parts of the body (metastases).
Read on to learn about the different stages of cancer and staging systems, how cancer stages are determined and classified, and their role in determining treatment plans.
The overall stage of cancer gives information on the location, extent, and severity of the disease. Cancer staging helps oncologists determine the best treatment option, such as surgery, radiotherapy, chemotherapy, immunotherapy, or hormone therapy.
If a cancer is small and localized, the patient may be offered surgery or radiation therapy initially; if it is larger or has spread, then systemic treatment such as chemotherapy might be preferred. It must be noted, however, that there are many other factors to consider when deciding the best treatment plan.
In addition to helping determine which treatment to give, cancer staging is also useful in informing how likely a treatment is to be successful and sets expectations for the road ahead. With many advanced cancers, the treatment aim is disease control, whereas with most early-stage cancers, the treatment aim is curative. By comparing similar cases in patients with the same stage of disease, it allows doctors to predict possible challenges and help the patient prepare.
Different stages of cancer also influence survival statistics and help determine prognosis — this is important not only for the patient but also for all healthcare professionals involved. Statistics on lung cancer published by the National Cancer Institute SEER program revealed that the five-year survival rate for distant disease was just 8% compared to 62.8% for those with localized disease. You can learn more about lung cancer and find out if you’re eligible for screening.
Finally, staging is also helpful for doctors to identify potential clinical trials and plays a vital role in cancer-related clinical research.
Different systems are used to stage cancer. Here’s a closer look at the most common systems used to determine different stages of cancer.
The TNM staging system is the most widely used for many types of cancer and allows standardization among practices. It gives detailed information on the primary tumor size (T), nodal disease (N), and metastases (M).
T gives information regarding the location and size of the primary tumor.
TX means the tumor cannot be measured or no information is available.
T0 means there is no primary tumor.
T1-4 gives information on the size and the extent of growth to nearby tissue. The higher the number, the larger the tumor, and the deeper it has invaded into nearby tissues.
N gives information on whether the cancer has spread to lymph nodes and how many are affected. Lymph nodes are small kidney- or bean-shaped organs that play a vital role in immune defense and help fight infection. They’re often the first point of spread of many cancers — cancer that originates in the lymph node is called lymphoma. Learn more about the signs and symptoms of lymphoma and other blood cancers.
NX means there is no information or it cannot be measured.
N0 means there is no lymph node involvement.
N1-N3 refers to the location and number of lymph nodes involved. The higher the number, the more nodes in which the cancer has spread. In some cancers, however, the number refers to the location of the lymph nodes instead of the number. The oncologist will explain what the numbers mean.
Note that N only refers to regional lymph nodes that are close to the site of the primary tumor. If the cancer has spread to distant lymph nodes, this is included in the M category.
Metastases is the term used to describe cancer that has spread from its primary site to one or more distant sites in the body.
M0 means there is no distant cancer spread.
M1 means that the cancer has spread to distant organs or tissues.
This gives an overview of the TNM staging system, however, it’s important to note that there is variation depending on the tumor type. Some types of cancer use subcategories within each domain using small letters to give more detail regarding the tumor’s size and location and its spread. The doctor will clearly explain what the staging means.
This is a less detailed staging system than the TNM staging system, and doctors sometimes use Roman numerals instead of numbers. The higher the number, the more advanced the cancer. Some cancers have a stage 0.
Stage 0: Cancer that has not become invasive, often called carcinoma in situ (in place). This means the cancer is still located in the place where it has arisen.
Stage I: Early stage, the cancer is small and has not spread to surrounding tissue or nearby lymph nodes. It is sometimes referred to as localized cancer.
Stage II: The cancer has grown more deeply into nearby tissue but has not spread.
Stage III: The cancer is larger and may have spread to surrounding tissue and/or lymph nodes.
Stage IV: The cancer has spread to at least one other part of the body from where it originated. This is referred to as metastatic cancer.
There are also certain types of cancer in which typical staging methods are not used — for example, blood cancer such as leukemia, brain cancer, and spinal cancer.
For some cancers, there are additional factors to be taken into account during staging, along with T, N, and M.
You may see tumors referred to as high-grade or low-grade, but what does this mean? The grade refers to the nature of the cancer cells and how abnormal they appear under a microscope. The grade is important as it gives an indication as to how quickly the cancer cells may grow and divide. As such, it helps the doctor predict how quickly a cancer might spread.
Grading is referred to as G and can be classified by numbers either 1-3 or 1-4, depending on the type of cancer. Higher numbers refer to a higher grade and less well-specialized cells. Grading is also important in helping oncologists make treatment decisions and inform prognosis. Higher-grade cancers tend to carry a poorer prognosis, and they vary in their response to certain treatments. For example, in non-Hodgkins lymphoma, higher-grade disease tends to respond better to chemotherapy than slower-growing, low-grade lymphomas.
In some types of cancer, tumor markers are important in predicting outcomes and monitoring disease response to treatment. These are certain markers found in the blood and monitored on blood tests. A well-known example of a tumor marker is prostate-specific antigen (PSA), which is used for staging prostate cancer and helps to inform a doctor’s decisions regarding treatment.
Tests are performed on cancer cells when a biopsy is taken to look for certain genes or receptors. An example of this is in breast cancer, when oncologists look for specific receptors such as hormone receptors. This allows doctors to give specific targeted therapies or hormone therapy that can affect outcomes.
Staging is typically performed at diagnosis before any treatment is given. Depending on the clinical situation, patients may need to be re-staged later down the line.
Clinical stage is based on a thorough assessment including physical examination, imaging such as X-rays, ultrasound, CT, MRI, nuclear medicine scans, and biopsy results. Occasionally, blood tests are used if tumor markers are important. Clinical staging informs initial treatment decisions and prognosis.
Pathological staging is performed after surgery if this is the initial treatment. It’s based on what is found during surgery along with assessment and investigations previously performed.
Staging may be performed again if the cancer progresses or has returned (recurrence). Doctors will use similar methods as they did at initial staging. Knowing if the cancer has spread and how far it has spread will help guide further treatment decisions.
Clinicians use an array of tests in order to determine different stages of cancer. Here’s a closer look.
Blood tests are used to detect specific markers in the blood, called tumor markers, which are either produced by cancer cells or in response to cancer cells. They can sometimes be used in staging and are often used to assess disease response or identify relapse.
Imaging techniques such as X-ray, ultrasound, CT, MRI and nuclear medicine scans are used for staging. The doctor may request multiple scans as some are better at giving a detailed view of the primary tumor while others (such as PET CT) are used to look for distant metastases. Learn more about imaging such as CT and MRI and their role in cancer detection.
This test involves a doctor inserting a thin tube with a camera into a natural opening (such as the mouth or rectum) for direct visualization. If cancer is suspected, biopsies are taken at the same time.
A biopsy is needed to confirm cancer diagnosis in most situations. This procedure involves taking a tissue sample from a site that looks suspicious. The tissue is looked at under a microscope by a pathologist. They determine if the cells look abnormal or cancerous and run further tests (such as molecular tests) to look for gene mutations.
Cancer staging gives an overview of the extent and spread of the disease, helping oncologists make decisions regarding the best treatment and the likelihood for success. The TNM staging system is the most widely used for determining different stages of cancer, and it’s based on results from biopsies, imaging, and occasionally blood tests.
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