Staging is a way of describing a cancer, such as where it is located, if or where it has spread, and if it is affecting the functions of other organs in the body. Doctors use diagnostic tests to determine the cancer's stage, so staging may not be complete until all of the tests are finished. Knowing the stage helps the doctor to decide what kind of treatment is best and can help predict a patient's prognosis (chance of recovery). There are different stage descriptions for different types of cancer.
There are two types of staging for prostate cancer. First, the clinical stage is based on the results of tests done before surgery, such as a biopsy, x-rays, CT scans, and bone scans. (X-rays, bone scans, and CT scans may not be necessary; they are recommended based on the level of serum PSA, the grade and volume of the cancer, and the clinical stage of the cancer.) Then, the pathologic stage is based on information found during surgery, plus the laboratory results (pathology) of the prostate tissue removed during surgery (which often includes the removal of the entire prostate and some lymph nodes).
One tool that doctors use to describe the stage is the TNM system. This system uses three criteria to judge the stage of the cancer: the tumor itself, the lymph nodes around the tumor, and if the tumor has spread to other parts of the body. The results are combined to determine the stage of cancer for each person. There are four stages: stages I through IV (one through four). The stage provides a common way of describing the cancer, so doctors can work together to plan the best treatments. After gathering information with the TNM method, the results can be grouped together into a simpler set of stages (called stage grouping). Many doctors do not use the TNM system and prefer another method called the Jewett-Whitmore staging system (stages A, B, C, and D). Both are described below.
Staging for prostate cancer involves reviewing test results to determine if the cancer has spread from the prostate to other parts of the body. The cancer is also given a grade (G), which is based on its appearance under a microscope, according to how much the cancer resembles healthy tissue.
TNM is an abbreviation for tumor (T), node (N), and metastasis (M). Doctors look at these three factors to determine the stage of cancer:
- How large is the primary tumor and where is it located? (Tumor, T)
- Has the tumor spread to the lymph nodes? (Node, N)
- Has the cancer metastasized to other parts of the body? (Metastasis, M)
Tumor. Using the TNM system, the "T" plus a letter or number (0 to 4) is used to describe the size and location of the tumor. Some stages are also divided into smaller groups that help describe the tumor in even more detail. Specific tumor stage information, based on the classification system that was implemented in 2002, is listed below.
TX: The primary tumor cannot be evaluated.
T0: There is no evidence of tumor in the prostate.
T1: The tumor cannot be felt during the DRE and is not seen during imaging (any test that produces pictures of the inside of the body, such as a CT scan). It may be found when surgery is done for another reason, usually for BPH, or abnormal growth of benign prostate cells.
T1a: The tumor is in 5% or less of the prostate tissue removed through surgery.
T1b: The tumor is in more than 5% of the prostate tissue removed through surgery.
T1c: The tumor is found during a needle biopsy, usually because the patient has an elevated PSA level.
T2: The tumor is found only within the prostate, not other areas of the body. It is large enough to be felt during the DRE.
T2a: The tumor has invaded one-half of one lobe (part or side) of the prostate.
T2b: The tumor has spread to more than one-half of one lobe of the prostate, but not to both lobes.
T2c: The tumor has invaded both lobes of the prostate.
T3: The tumor extends through the prostate capsule (into the tissue just outside the prostate on one side).
T3a: The tumor extends through the prostate capsule either unilaterally (on one side) or bilaterally (on both sides of the prostate).
T3b: The tumor has invaded the seminal vesicle(s), the tube(s) that carry semen.
T4: The tumor is fixed, or it is invading nearby structures besides the seminal vesicles, such as the neck of the bladder, the external sphincter (part of the body that helps to control urination), the rectum, levator muscles, and/or the pelvic wall.
Nodes. The “N” in the TNM staging system stands for lymph nodes, the tiny, bean-shaped organs that help fight infection. Lymph nodes near the prostate in the pelvic region are called regional lymph nodes. Lymph nodes in other parts of the body are called distant lymph nodes.
NX: The regional lymph nodes cannot be evaluated.
N0: There is no regional lymph node metastasis.
N1: The prostate cancer has invaded the regional lymph node(s).
Distant metastasis. The "M" in the TNM system indicates whether the prostate cancer has spread to other parts of the body (to areas such as the lungs or the bones).
MX: Distant metastasis cannot be evaluated.
M0: The disease has not metastasized.
M1: There is distant metastasis.
M1a: The cancer has invaded nonregional, or distant, lymph node(s).
M1b: The cancer has invaded bone(s) in the body.
M1c: The cancer has reached another part of the body.
Grade. Doctors may also use the term “grade,” which describes how much the tumor appears like healthy tissue. The grade of a cancer can help the doctor to predict how quickly the cancer might grow. In cancer that resembles healthy tissue, doctors can clearly see different types of cells grouped together (called well differentiated). In a higher-grade cancer, the cancer cells usually look less like healthy cells, or “wilder” (called poorly differentiated or undifferentiated). In general, tumors with more differentiated cells have a better prognosis.
The Gleason System is the most common prostate cancer grading system used. This method looks at how the cancer cells are arranged in the prostate and grades them based on a scale of 1 to 5. The doctor looks for a pattern of cell growth, and adds the score to come up with an overall score. The interpretation of the Gleason score by physicians has changed in recent years. Originally, there was a broader spread, with physicians using a range of scores. Today, doctors tend to describe a score of 6 is a low-grade cancer, 7 is medium-grade, and a score of 8, 9, or 10 is high-grade cancer. A lower-grade cancer grows more slowly and is less likely to spread than a cancer with a higher grade.
The TNM system uses the letter "G" to define a grade for prostate cancer.
GX: The grade cannot be evaluated.
G1: The cells are well-differentiated (Gleason 6 or less).
G2: The cells are moderately differentiated (Gleason 7).
G3: The cells are poorly differentiated or undifferentiated (Gleason 8 to 10).
Cancer stage grouping. Doctors assign the stage of the cancer by combining the T, N, and M classification and the grade. As mentioned above, some doctors prefer to use the Jewett-Whitmore staging system (stages A, B, C, and D).
Stage I or Stage A: Cancer is found in the prostate only, usually during another medical procedure. It cannot be felt during the DRE. A stage I cancer usually contains well-differentiated cells and is predicted to grow slowly. This can also be called stage A1 prostate cancer when it affects only one lobe of the prostate and stage A2 when both prostate lobes are involved (T1a, N0, M0, G1).
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Stage II or Stage B: The doctor can feel the tumor during a DRE. There is no evidence that it has spread beyond the prostate gland, but the cells are usually more abnormal and may tend to grow more quickly. (It has not spread to lymph nodes or distant organs.) Stage II prostate cancer may also be called stage A2, stage B1, or stage B2 prostate cancer (T1, T2, T3; N0; M0; any G).
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Stage III or Stage C: The cancer has spread beyond the outer layer of the prostate into nearby tissues. It may also have spread to the seminal vesicles, the glands in men that help produce semen (T3, N0, M0, any G).
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Stage IV or Stage D: This describes any tumor of any grade (any G) that has spread to other areas of the body such as the bladder or rectum (T4, N0, M0); bone, liver, lungs (any T, N0, M1); or lymph nodes (any T, N1, M0). Stage IV prostate cancer may also be called stage D1 or D2 prostate cancer.
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Recurrent: Recurrent prostate cancer is cancer that comes back after treatment. It may come back in the prostate area again or in other parts of the body.
Used with permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original source for this material is the AJCC Cancer Staging Manual, Sixth Edition (2002) published by Springer-Verlag New York, www.cancerstaging.net.
Last Updated: October 07, 2009
