Staging is used to describe how far cancer has spread. The Gleason score provides a system of grading prostate cancer. The Gleason score should not be confused with staging.
To determine the Gleason score, tissue samples are examined under a microscope. Gleason scores range from 2 to 10 based on cellular characteristics, and indicate the aggressiveness of the cancer. A low Gleason score means the cancer tissue is similar to normal prostate tissue and the tumor is less likely to spread. A high Gleason score means the cancer tissue is very different from normal and the tumor is more likely to spread.
The Gleason score, together with staging, helps providers determine the most effective treatment strategy.
The following clinical stages are used for prostate cancer:
Stage I: Cancer is found in the prostate only, and has not spread beyond one-half of one lobe of the prostate. The cancer may be found by needle biopsy or in a small amount of tissue during surgery for other reasons.
Stage IIA: Cancer is found in the prostate only, and may or may not have spread beyond one-half of one lobe of the prostate.
Stage IIB: Cancer is found in the prostate only, but is found in opposite sides of the prostate.
Stage III: Cancer has spread beyond the outer layer of the prostate and may have spread to the seminal vesicles.
Stage IV: Cancer has spread beyond the seminal vesicles to nearby tissue or organs, such as the rectum, bladder, or pelvic wall; to nearby lymph nodes; or to distant parts of the body, such as the bones.