Grades and stages of prostate cancer

Measuring the grade and stage of prostate cancer helps doctors decide how to treat it.

Grades, Gleason score and grade groups 

The grade of a cancer helps doctors predict how quickly the prostate cancer is likely to grow and spread. Doctors use a scale called the Gleason score to measure and report the grade of prostate cancer.  The Gleason score is based on how abnormal the cells appear in the two largest areas of the tumor. The pathologist assigns a score of 1-5 for each area and adds them together for the Gleason score. Although Gleason scores can range from 2-10, most prostate cancers will be scored as 6 or higher. The higher the score, the more abnormal and aggressive the cells appear. 

• A score of 6 is low grade.
• A score of 7 is intermediate grade.
• A score of 8 to 10 is high grade.

An updated "grade group" system is now in use. A grade group score is related to a Gleason score:

• Grade Group 1: Gleason score <=6
• Grade Group 2: Gleason score = 7 (3+4)
• Grade Group 3: Gleason score = 7 (4+3)
• Grade Group 4: Gleason score = 8
• Grade Group 5: Gleason score = 9-10

Staging

The stage refers to whether the cancer has spread beyond the prostate, and if it has, the location in the body where it has spread. Doctors use the following information to stage prostate cancer:

• size of the tumor
• whether the cancer has spread to nearby lymph nodes 
• the presence or absence of spread beyond the prostate and lymph nodes (metastasis) 
• PSA levels at the time of diagnosis
• Gleason score

Using this information, prostate cancer is grouped into four stages, with Stage 1 being the least advanced and Stage 4 being the most advanced.

• Stage 1 cancer is contained to the prostate, has a Gleason score of 6 or below and a PSA level of less than 10.
• Stage 2 cancer is more advanced but has not spread beyond the prostate.
• Stage 3 cancer extends beyond the prostate but has not spread to lymph nodes.
• Stage 4 (metastatic prostate cancer) has spread to another part of the body outside of the prostate. Common areas of spread include the bladder, rectum, lymph nodes or bones.

Additional tests for staging

After grading and staging, additional tests or imaging may be done to check for cancer spread, though these are not required for all men with newly diagnosed prostate cancer.

Additional tests are run if:

• PSA levels are high
• The Gleason score is high
• The cancer is large
• The cancer has spread to lymph nodes or beyond

The tests may include:

• Computed tomography (CT) scans of the abdomen and pelvis
• Bone scans
• Magnetic resonance imaging (MRI) of your pelvis
• Positron emission tomography (PET) scans.
• Pelvic lymph node dissection (PLND)

Additional tests may be performed on blood or tissue to help guide treatment. For some patients, these tests may help guide the choice of immunotherapy or targeted therapy.