If you or a loved one has been diagnosed with prostate cancer, you may already be familiar with the Gleason scale. It was developed by physician Donald Gleason in the 1960s. It provides a score that helps predict the aggressiveness of prostate cancer.
A pathologist begins by examining tissue samples from a prostate biopsy under a microscope. To determine the Gleason score, the pathologist compares the cancer tissue pattern with normal tissue.
According to the National Cancer Institute (NCI), cancer tissue that looks most like normal tissue is grade 1. If the cancer tissue spreads through the prostate and deviates widely from the features of normal cells, it is grade 5.
The pathologist assigns two separate grades to the two predominant cancer cell patterns in the prostate tissue sample. They determine the first number by observing the area where the prostate cancer cells are most prominent. The second number, or secondary grade, relates to the area where the cells are almost as prominent.
These two numbers added together produce the total Gleason score, which is a number between 2 and 10. A higher score means the cancer is more likely to spread.
When you discuss your Gleason score with your doctor, ask about both the primary and secondary grade numbers. A Gleason score of 7 can be derived from differing primary and secondary grades, for example 3 and 4, or 4 and 3. This can be significant because a primary grade of 3 indicates that the predominant cancer area is less aggressive than the secondary area. The reverse is true if the score results from a primary grade of 4 and secondary grade of 3.
The Gleason score is only one consideration in establishing your risk of advancing cancer, and in weighing treatment options. Your doctor will consider your age and overall health as well as additional tests to determine the cancer stage and risk level. These tests include:
Your doctor will also consider your level of prostate-specific antigen (PSA), a protein produced by cells in the prostate gland. PSA is measured in nanograms per milliliter of blood (ng/ml). PSA level is another important factor in assessing the risk of advancing cancer.
According to the NCI, a Gleason score of 6 or lower, a PSA level of 10 ng/ml or less, and an early tumor stage places you in the low-risk category. Together, these factors mean that the prostate cancer is unlikely to grow or spread to other tissues or organs for many years.
Some men in this risk category monitor their prostate cancer with active surveillance. They have frequent checkups that may include:
- PSA tests
- ultrasound or other imaging
- additional biopsies
A Gleason score of 7, a PSA between 10 and 20 ng/ml, and a medium tumor stage indicates medium risk. This means that the prostate cancer is unlikely to grow or spread for several years. You and your doctor will consider your age and overall health when weighing treatment options, which may include:
- combination of these
A Gleason score of 8 or higher, accompanied by a PSA level of higher than 20 ng/ml and a more advanced tumor stage, signifies a high risk of advancing cancer. In high-risk cases, the prostate cancer tissue looks very different from normal tissue. These cancerous cells are sometimes described as being “poorly differentiated.” These cells may still be considered early-stage prostate cancer if the cancer has not spread. High risk means the cancer is likely to grow or spread within a few years.
A higher Gleason score generally predicts that prostate cancer will grow more quickly. However, remember that the score alone does not predict your prognosis. When you evaluate treatment risks and benefits with your doctor, be sure that you also understand the cancer stage and your PSA level. This knowledge will help you decide whether active surveillance is appropriate. It can also help guide you in selecting the treatment that best suits your situation.