Prostate Cancer

Staging & Grading

After diagnosing your cancer, your doctor needs to determine the extent of the disease so he or she can recommend the best treatment approach for you. Determining the extent of your cancer is called staging.

The tumor, node, metastasis (TNM) classification developed by the American Joint Committee on Cancer (AJCC) is the primary system used to stage prostate cancer. The first step in staging is to assign a clinical stage, which is based on the results of a prostate biopsy, physical examinations and imaging studies (such as bone scans or computed tomography). These tests enable the doctor to estimate the size and location of the tumor (T category), and to determine whether the cancer has spread to nearby lymph nodes (N category) or other parts of the body (M category) (see Table 1). A pathologist may confirm the stage by examining tissue removed during surgery or biopsy. The stage determined by the pathologist is called the pathologic stage.

The AJCC classification is then used to determine an overall stage of disease (see Table 2). Stage I or II prostate cancer is considered early stage. At these stages, the tumor is contained within the prostate. Stage III or IV is considered advanced. At these stages, the tumor extends outside of the prostate and/or involves nearby tissues, such as lymph nodes or the bladder. Stage III is also known as locally advanced prostate cancer because it has extended beyond the prostate but is still confined to the area near the prostate. Stage IV cancer may be either regional disease, which means the cancer has spread to nearby lymph nodes but not to other parts of the body, or distant disease, which means the cancer has spread to distant lymph nodes, bone or other organs (see Figure 1).

In addition to establishing a pathologic stage, the pathologist will study the biopsy sample to determine the tumor grade, which indicates how closely the tumor cells resemble normal cells. This grade is known as the Gleason score and ranges from two to 10. The pathologist will assign low scores when the tumor looks more like normal prostate tissue and high scores when the cancer looks less like normal tissue. Your doctor may call cancer that looks less like normal tissue “less differentiated,” “poorly differentiated” or “undifferentiated.” The higher the Gleason score, the more aggressive the tumor is (the more likely it is to spread). For example:

  • Gleason 6 – Tumor tissue is well differentiated, less aggressive and more likely to grow slowly.
  • Gleason 7 – Tumor tissue is somewhat differentiated, moderately aggressive and likely to grow, but it is less likely to spread quickly.
  • Gleason 8 to 10 – Tumor tissue is poorly differentiated or undifferentiated, very aggressive and likely to grow quickly and very likely to spread.

Your doctor will consider your Gleason score, stage and PSA level when planning the best treatment for you.

Some advanced prostate cancers at first appear to be early-stage cancers. In these cases, local therapy, such as surgery or radiation therapy, is often given; however, these may not help if cancer cells have already spread beyond the prostate. In these cases, a rise in the prostate-specific antigen (PSA) level after surgery or radiation therapy usually indicates that the prostate cancer is advanced. As long as the PSA level is undetectable or very low, no other tests for advanced prostate cancer are needed. The PSA test is the best indication of the cancer’s progression and should be monitored regularly throughout your life, even after treatment ends. If your PSA level begins to increase steadily, your doctor may order additional tests to determine whether the cancer has recurred or spread.

Table 1. TNM system for classifying prostate cancer

Classification Definition
Tumor (T)
Tx Primary tumor cannot be assessed.
T0 No evidence of primary tumor.
T1*

  T1a

  T1b
  T1c
Tumor is not detected during a digital rectal exam (DRE) and cannot be seen on imaging studies (tumor may be discovered during surgery for a reason other than cancer).
Tumor is found during surgery not related to prostate cancer, and tumor cells are found in 5 percent or less of the surgically removed prostate tissue.
Tumor cells are found in more than 5 percent of the surgically removed prostate tissue.
Tumor cells found in a sample obtained by needle biopsy, which is done because of an elevated prostate-specific antigen (PSA) level.
T2
  T2a
  T2b
  T2c
Tumor can be detected during DRE and is present in the prostate only.
Tumor is in half or less of one side (lobe) of the prostate.
Tumor is in more than half of one prostate lobe, but it has not invaded the other lobe.
Tumor is in both prostate lobes.
T3
  T3a
Tumor extends outside of the prostate.
Tumor extends outside the prostate on one side or both sides.
T4 Tumor has spread to tissues near the prostate other than the seminal vesicles, such as the bladder or wall of the pelvis.
Nodes (N)
Nx Nearby lymph nodes were not evaluated.
N0 No cancer is detected in nearby lymph nodes.
N1 Cancer cells are found in nearby lymph nodes./td>
Metastasis (M)
M0
M1
  M1a
  M1b
  M1c
Cancer has not spread beyond nearby lymph nodes.
Cancer is detected in tissue beyond nearby lymph nodes.
Cancer is detected in distant lymph nodes.
Cancer is detected in the bone.
Cancer is detected in another organ or site, with or without cancer in the bone.

*When a tumor is found during surgery not related to prostate cancer, it’s further classified as T1a if tumor cells are found in 5 percent or less of the surgically removed prostate tissue, or as T1b if tumor cells are found in more than 5 percent of the surgically removed prostate tissue. A tumor is classified as T1c if it’s found during a needle biopsy, which is done because of an elevated prostate-specific antigen (PSA) level. If a tumor is found during a needle biopsy, it is classified as T1c.

Table 2. AJCC Prognostic Stage Groups

Group/stage TNM classification Gleason score Prostate-specific antigen (PSA) level
I
T1(a-c), N0, M0
T2a, N0, M0
6 or less, or unknown
6 or less, or unknown
Less than 10, or unknown
Less than 10, or unknown
IIA
T1(a-c), N0, M0
T1(a-c), N0, M0
T2a, N0, M0
T2a or T2b, N0, M0
T2b, N0, M0
7
6 or less
6 or less
7 or less
Unknown
Less than 20
10 or higher, but less than 20
10 or higher, but less than 20
Less than 20
Unknown
IIB
T2c, N0, M0
T1 or T2, N0, M0
T1 or T2, N0, M0
Any score
Any score
8 or higher
Any level
20 or higher
Any level
III T3(a-b), N0, M0 Any score Any level
IV
T4, N0, M0
Any T, N1, M0
Any T, Any N, M1
Any score
Any score
Any score
Any level
Any level
Any level

 

Figure 1. Stages of prostate cancer

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