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
Clinically inapparent (produces no signs or symptoms) tumor that is not palpable (noticeable by touch).
Tumor incidental histologic finding in 5 percent or less of tissue resected.
Tumor incidental histologic finding in more than 5 percent of tissue resected.
Tumor identified by needle biopsy found in one or both sides, but not palpable (noticeable by touch).
T2
  T2a
  T2b

  T2c
Tumor is palpable (noticeable by touch) and confined within prostate.
Tumor involves one-half of one side (one prostate lobe) or less.
Tumor involves more than one-half of one side (one prostate lobe) but not both sides (both lobes).
Tumor involves both sides (prostate lobes).
T3

  T3a
  T3b
Extraprostatic tumor (tumor extends beyond the prostate gland) that is not fixed or does not invade adjacent structures.
Extraprostatic extension (tumor extends beyond the prostate gland) (unilateral or bilateral).
Tumor invades seminal vesicle(s) (gland on each side of the bladder).
T4 Tumor is fixed or invades adjacent structures other than seminal vesicles such as external sphincter, rectum, bladder, levator muscles and/or pelvic wall.
Node (N)
NX Regional nodes were not assessed.
N0 No positive regional nodes.
N1 Metastases in regional node(s).
Metastasis (M)
M0 No distant metastasis.
M1
  M1a
  M1b
  M1c
Distant metastasis.
Nonregional lymph node(s).
Bone(s).
Other site(s) with or without bone disease.

Table 2. AJCC Prognostic Stage Groups

Group/stage TNM classification Gleason grade Prostate-specific antigen (PSA) level
I
T1a-c, N0, M0
T2a, N0, M0
1
1
Less than 10
Less than 10
IIA
T1a-c, N0, M0
T2a, N0, M0
T2b-c, N0, M0
1
1
1
Greater than or equal to 10, but less than 20
Greater than or equal to 10, but less than 20
Less than 20
IIB
T1-2, N0, M0
2
Less than 20
IIC
T1-2, N0, M0
T1-2, N0, M0
3
4
Less than 20
Less than 20
IIIA T1-2, N0, M0 1-4 Greater than or equal to 20
IIIB T3-4, N0, M0 1-4 Any level
IIIC Any T, N0, M0 5 Any level
IVA
Any T, N1, M0
Any grade
Any level
IVB
Any T, Any N, M1
Any grade
Any level

Used with permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original and primary source for this information is the AJCC Cancer Staging Manual, Eighth Edition (2017) published by Springer Science+Business Media.

 

Figure 1. Stages of prostate cancer

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