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What is Cancer Staging

Staging Cancer

Contents
1.What is staging?
2.What is the basis for staging?
3.What are the common elements of staging systems?
1.What is the TNM system?
2.Stage Definition
4.Are all cancers staged with TNM classifications?
5.What types of tests are used to determine stage?

What is staging?
Staging describes the extent or severity of an individual’s cancer based on the extent of the original (primary) tumor and the extent of spread in the body. Staging is important:

Staging helps the doctor plan a person’s treatment.
The stage can be used to estimate the person’s prognosis (likely outcome or course of the disease).
Knowing the stage is important in identifying clinical trials (research studies) that may be suitable for a particular patient.
Staging helps researchers and health care providers exchange information about patients. It also gives them a common language for evaluating the results of clinical trials and comparing the results of different trials.

What is the basis for staging?
Staging is based on knowledge of the way cancer develops. Cancer cells divide and grow without control or order to form a mass of tissue, called a growth or tumor. As the tumor grows, it can invade nearby organs and tissues. Cancer cells can also break away from the tumor and enter the bloodstream or lymphatic system. By moving through the bloodstream or lymphatic system, cancer can spread from the primary site to form new tumors in other organs. The spread of cancer is called metastasis.

What are the common elements of staging systems?
Staging systems for cancer have evolved over time. They continue to change as scientists learn more about cancer. Some staging systems cover many types of cancer; others focus on a particular type. The common elements considered in most staging systems are:

Location of the primary tumor,
Tumor size and number of tumors,
Lymph node involvement (spread of cancer into lymph nodes),
Cell type and tumor grade* (how closely the cancer cells resemble normal tissue), and
Presence or absence of metastasis.
What is the TNM system?
The TNM system is one of the most commonly used staging systems. This system has been accepted by the International Union Against Cancer (UICC) and the American Joint Committee on Cancer (AJCC). Most medical facilities use the TNM system as their main method for cancer reporting. PDQ®, the NCI’s comprehensive cancer database, also uses the TNM system.

The TNM system is based on the extent of the tumor (T), the extent of spread to the lymph nodes (N), and the presence of metastasis (M). A number is added to each letter to indicate the size or extent of the tumor and the extent of spread.

Primary Tumor (T)
TX Primary tumor cannot be evaluated
T0 No evidence of primary tumor
Tis Carcinoma in situ (early cancer that has not spread to neighboring tissue)
T1, T2, T3, T4 Size and/or extent of the primary tumor

Regional Lymph Nodes (N)
NX Regional lymph nodes cannot be evaluated
N0 No regional lymph node involvement (no cancer found in the lymph nodes)
N1, N2, N3 Involvement of regional lymph nodes (number and/or extent of spread)

Distant Metastasis (M)
MX Distant metastasis cannot be evaluated
M0 No distant metastasis (cancer has not spread to other parts of the body)
M1 Distant metastasis (cancer has spread to distant parts of the body)

For example, breast cancer T3 N2 M0 refers to a large tumor that has spread outside the breast to nearby lymph nodes, but not to other parts of the body. Prostate cancer T2 N0 M0 means that the tumor is located only in the prostate and has not spread to the lymph nodes or any other part of the body.

For many cancers, TNM combinations correspond to one of five stages. Criteria for stages differ for different types of cancer. For example, bladder cancer T3 N0 M0 is stage III; however, colon cancer T3 N0 M0 is stage II.

Stage Definition
Stage 0 Carcinoma in situ (early cancer that is present only in the layer of cells in which it began).
Stage I, Stage II, and Stage III Higher numbers indicate more extensive disease: greater tumor size, and/or spread of the cancer to nearby lymph nodes and/or organs adjacent to the primary tumor.
Stage IV The cancer has spread to another organ.

Are all cancers staged with TNM classifications?
Most types of cancer have TNM designations, but some do not. For example, cancers of the brain and spinal cord are classified according to their cell type and grade. Different staging systems are also used for many cancers of the blood or bone marrow, such as lymphoma. The Ann Arbor staging classification is commonly used to stage lymphomas and has been adopted by both the AJCC and the UICC. However, other cancers of the blood or bone marrow, including most types of leukemia, do not have a clear-cut staging system. Another staging system, developed by the International Federation of Gynecology and Obstetrics, is used to stage cancers of the cervix, uterus, ovary, vagina, and vulva. This system uses the TNM format. Additionally, childhood cancers are staged using either the TNM system or the staging criteria of the Children’s Oncology Group, a group that conducts pediatric clinical trials.

Many cancer registries, such as the NCI’s Surveillance, Epidemiology, and End Results Program (SEER), use summary staging. This system is used for all types of cancer. It groups cancer cases into five main categories:

1.In situ is early cancer that is present only in the layer of cells in which it began.
2.Localized is cancer that is limited to the organ in which it began, without evidence of spread.
3.Regional is cancer that has spread beyond the original (primary) site to nearby lymph nodes or organs and tissues.
4.Distant is cancer that has spread from the primary site to distant organs or distant lymph nodes.
5.Unknown is used to describe cases for which there is not enough information to indicate a stage.
 

What types of tests are used to determine stage?
The types of tests used for staging depend on the type of cancer. Tests include the following:

Physical exams are used to gather information about the cancer. The doctor examines the body by looking, feeling, and listening for anything unusual. The physical exam may show the location and size of the tumor(s) and the spread of the cancer to the lymph nodes and/or to other organs.

Imaging studies produce pictures of areas inside the body. These studies are important tools in determining stage. Procedures such as x-rays, computed tomography (CT) scans, magnetic resonance imaging (MRI) scans, and positron emission tomography (PET) scans can show the location of the cancer, the size of the tumor, and whether the cancer has spread.

Laboratory tests are studies of blood, urine, other fluids, and tissues taken from the body. For example, tests for liver function and tumor markers (substances sometimes found in increased amounts if cancer is present) can provide information about the cancer.

Pathology reports may include information about the size of the tumor, the growth of the tumor into other tissues and organs, the type of cancer cells, and the grade of the tumor (how closely the cancer cells resemble normal tissue). A biopsy (the removal of cells or tissues for examination under a microscope) may be performed to provide information for the pathology report. Cytology reports also describe findings from the examination of cells in body fluids.

Surgical reports tell what is found during surgery. These reports describe the size and appearance of the tumor and often include observations about lymph nodes and nearby organs.

 


 

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