Understanding Prostate Cancer: The Gleason Scale
Knowing the Numbers
If you or a loved one has been diagnosed with prostate cancer, you may already be familiar with the Gleason scale. The Gleason scale, developed by physician Donald Gleason in the 1960s, provides a score that helps predict the aggressiveness of prostate cancer.
Here is a look at what the numbers mean, how to interpret your results, and where the scale fits in with the outcomes of other tests.
Understanding the Scale
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 has spread through the prostate and deviates widely from the features of normal cells, it is grade 5.
The Sum of Two Numbers
The pathologist assigns two separate grades to the two predominant cancer cell patterns in the prostate tissue samples. The first number, called the primary grade, is determined by observing the area where the prostate cancer cells are most prominent. The second number, or secondary grade, considers the area where the cells are almost as prominent.
These two numbers added together produce the total Gleason score or sum. This is a number between 2 and 10. A higher score means the cancer is more likely to spread.
Know Both Numbers of Your Gleason Sum
When you discuss your Gleason sum 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.
One of Many Factors
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 group. These tests include digital rectal exam (DRE), bone scan, MRI or CT scan.
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 10-20 ng/ml, 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 DREs, PSA tests, ultrasound or other imaging, and 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 surgery, radiation, medication, or a combination of these.
A Gleason score of 8 or higher, accompanied by PSA level 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.” This point is still considered early-stage prostate cancer because the cancer has not spread. High risk means the cancer is likely to grow or spread within a few years.
Keeping the Numbers in Perspective
While a higher Gleason score generally predicts that prostate cancer will grow more quickly, 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 or guide you in selecting treatment that best suits your condition.
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