Cancer develops when abnormal cells in the body grow out of control and fail to die when they should. These abnormal cells can grow into clumps known as tumors.
Cancer staging is the process used by doctors to determine how much cancer is in the body and where it is located. Knowing the stage of cancer is important to help doctors determine the best course of treatment.
Knowing the cancer stage also helps the doctors estimate a patient’s prognosis, which is the most likely outcome including the chance of recovery or having the cancer come back.
In general, cancer is given a designation of stage 1, stage 2, stage 3, or stage 4. The higher the number, the more the cancer has grown and the worse the prognosis will be.
Cancer is staged using one of several staging systems. Some systems are used to describe a particular type of cancer, such as prostate cancer. Blood cancers such as leukemia do not have a clear staging system.
Cancer staging systems continue to be refined as researchers learn more about cancer and how it grows.
The TNM system is one of the most commonly used cancer staging systems.
• T stands for the tumor, including size and number of tumors found.
• N stands for lymph nodes, which are collection areas for lymphatic fluid. This fluid is part of the immune system that helps filter cancer cells and bacteria out of the body.
• M stands for metastasis. When cancer cells break away from the initial tumor, they can travel through the blood or the lymph system to other parts of the body and form new tumors. These tumors are called metastases. The number of metastases is significant in staging cancer.
In each of these cases, the doctor will determine a rating for each element of the TNM system.
• TX means the primary tumor cannot be evaluated.
• T0 means there is no sign of a primary tumor.
• Tis means carcinoma in situ (CIS) which is an indication that there are abnormal cells present but they have not spread into surrounding tissue. CIS is not cancer, but is often considered to be a “pre-cancer” which often becomes cancer.
• T1, T2, T3, or T4 indicates the size and seriousness of the primary tumor. A higher number indicates more serious disease.
A similar rating is given to cancerous lymph nodes:
• Nx means regional lymph nodes cannot be evaluated.
• N0 means no nodes are involved.
• N1, N2, N3, or N4 shows how many nodes are involved or how much the cancer has spread. A higher number means the cancer has spread further.
These are the ratings for metastasis in other parts of the body:
• MX means distant metastasis cannot be evaluated.
• M0 means there is no metastasis or tumor growth in other parts of the body.
• M1 means the cancer has created a metastasis somewhere else in the body.
Once the TNM numbers have been determined, the doctor combines this information to assign a stage to the cancer.
• Stage 0 is sometimes used to indicated CIS or pre-cancer.
• Stage 1, stage 2, or stage 3 cancer shows a progressively more serious cancer. A higher number means the tumor is larger or the cancer has spread into surrounding tissue or lymph nodes.
• Stage 4 cancer indicates the cancer has spread to one or more other organs or tissues in other parts of the body. Stage 4 cancer is the most serious stage.
Depending on the type of cancer, the doctor may consider other factors in addition to TNM when determining the stage of the cancer. Tests to help determine cancer stages include physical exams, imaging such as CT or MRI scans, laboratory tests including examination of small pieces of the tumor under a microscope.
It is important to note that the stage of a cancer is only determined one time -- at the initial diagnosis. The stage of the cancer will not change as the disease progresses or is eliminated.
The doctor uses the stage as the starting point for all treatments that follow the initial diagnosis. So for example, a cancer that is initially designated stage 2 that has not spread into any surrounding lymph nodes and has not metastasized will continue to be called stage 2 cancer even if it later spreads to other parts of the body.
Stage 1 cancer is considered to be the least serious and easiest to treat with the best outlook for recovery. Stage 4 cancer is the most serious. But in many cases, cancer of any stage can be treated. Talk to your healthcare provider if you have any questions or concerns about cancer.
Sources:
National Cancer Institute. Cancer Staging. Web. September 26, 2011.
http://www.cancer.gov/cancertopics/factsheet/detection/staging
American Cancer Society. Staging. Web. September 26, 2011.
http://www.cancer.org/Treatment/UnderstandingYourDiagnosis/staging
American Joint Committee on Cancer. What is Cancer Staging?. Web. September 26, 2011.
http://www.cancerstaging.org/mission/whatis.html
MedicineNet.com. Definition of Lymph node. Web. September 26, 2011.
http://www.medterms.com/script/main/art.asp?articlekey=4213
Reviewed September 27, 2011
by Michele Blackberg RN
Edited by Jody Smith