Few organs of the human body get as much scrutiny as the male prostate gland. Medicine has developed numerous ways to treat all diseases of the prostate, especially cancer. To treat prostate cancer effectively oncologists need to classify the cancer's stage of growth and how fast it's growing.

Prostate cancer stages describe how far a cancer of the prostate has spread. Doctors define stages in determining treatment for prostate cancer and in predicting the chances of recovery.

Prostate cancer stages are determined by evaluating the prostate tissue and determining its Gleason score (a microscopic assessment of the cells’ architecture used to predict the aggressiveness of the cancer), the prostate specific antigen (PSA) level, digital rectal exam (DRE), and imaging test results.

There are really two types of stages: the clinical stage and the pathologic stage:

• The clinical stage is determined by all of the above factors before a man has undergone surgery to remove the prostate.
• The pathologic stage is determined by the above factors after a man has undergone surgery and the removed prostate tissue is evaluated (as opposed to biopsy tissue).

As a result, a man’s stage can change after he has had surgery and evaluation of either the prostate or nearby tissues revealed findings not known prior to surgery.

There are a number of different systems used to define prostate cancer stages; among them are the Whitmore-Jewett system and the D’Amico systems. But the most common staging system by far is the American Joint Committee on Cancer’s TNM system.

What Is the TNM System?

The TNM system is based on five factors:

• The size and location of the Tumor (how much of the prostate it occupies or if it is limited/not limited to the prostate).
• Whether or not the cancer has spread to the lymph Nodes.
• Whether or not the cancer has spread or Metastasized to other parts of the body.
• The Gleason score of the prostate tissue (either from surgery or biopsy).
• The PSA level when the man was diagnosed with prostate cancer.

There are four T categories (T1-T4) with the first three categories each divided into subcategories. There are three N categories (NX, meaning the lymph nodes were not evaluated, and N0-N1). There are two M categories (M0-M1), with M1 divided into subcategories. Doctors may use any of a number of imaging tests, including magnetic resonance imaging (MRI), computed tomography (CT), positive emission tomography (PET), bone scan, or lymph node biopsy to determine the TNM status.

What Are the Prostate Cancer Stages?

Prostate cancer stages are determined by combining the T, N, and M categories with the Gleason score and the PSA level at the time of diagnosis. Combining these factors is called “stage grouping” and the result is the assignment of a Roman numeral stage from I to IV. The higher the stage number, the more advanced the cancer.

If you have received a prostate cancer diagnosis, your doctor will want to ascertain the grade (or Gleason score) and stage of your cancer. The grade and stage will determine treatment, which could include active surveillance. Stage 1 and stage 2 cancer are typically encapsulated within the organ. Stage 3 cancer is typically recognized via digital rectal exam, and stage 4 cancer has broken out the organ and invaded nearby organs and structures.

STAGE I PROSTATE CANCER is defined as either:

• T1, N0, M0, Gleason = or <6, PSA 10: The cancer is localized to the prostate with no spread beyond the gland. Your doctor cannot feel the tumor by digital rectal exam (DRE) or visualize it by an imaging test.
• vT2a, N0, M0, Gleason = or <6, PSA<10: The cancer is localized to the prostate with no spread beyond the gland. The tumor can be felt by DRE or visualized by an imaging test but is limited to half or less of one side of the gland.

STAGE IIA PROSTATE CANCER is defined as either:

• T1, N0, M0, Gleason = 7, PSA<20: The cancer is localized to the prostate with no spread beyond the gland. Your doctor cannot feel the tumor by DRE or visualize it by an imaging test.
• T1, N0, M0, Gleason = or <6, PSA = or >10 but <20: The cancer is localized to the prostate with no spread beyond the gland. Your doctor cannot feel the tumor by DRE or visualize it by an imaging test.

STAGE IIB PROSTATE CANCER is defined as either:

• T2c, N0, M0, and Gleason score, any PSA: The cancer is localized to the prostate with no spread beyond the gland. The tumor can be felt by DRE or visualized by an imaging test and is in both sides of the gland.
• T1 or T2, N0, M0, any Gleason score, PSA = or >20: The cancer is localized to the prostate with no spread beyond the gland. The tumor may or may not be felt by DRE or visualized by an imaging test.
• T1 or T2, N0, M0, Gleason = or >8, any PSA: The cancer is localized to the prostate with no spread beyond the gland. The tumor may or may not be felt by DRE or visualized by an imaging test.

STAGE III PROSTATE CANCER is defined as:

• T3, N0, M0, any Gleason score, any PSA: The cancer has grown outside the prostate and may have grown into the seminal vesicles but has not spread to lymph nodes or other places in the body.

STAGE IV PROSTATE CANCERr is defined as either:

• T4, N0, M0, any Gleason score, any PSA: The cancer has not spread to lymph nodes or distant locations in the body but has spread to nearby tissues (aside from the seminal vesicles) such as rectum, bladder, pelvic wall, or urethral sphincter.
• Any T, N1, M0, any Gleason score, any PSA: The cancer may or may not have spread to nearby tissues and has spread to nearby lymph nodes. The cancer has not spread to distant locations in the body.
• Any T, any N, M1, any Gleason score, any PSA: The cancer may or may not have spread to nearby tissues and/or lymph nodes. The cancer has spread to distant locations in the body.

Researchers have studied the efficacy of different prostate cancer treatment strategies based upon prostate cancer stages. Your doctor will use this information, factoring in your age and overall health, to determine what treatment strategy they recommend for you.

Originally published in May 2016 and updated.