What is the Gleason Score for Prostate Cancer?
You might be familiar with the term ‘Gleason Score’ if you or a loved one has had a biopsy for prostate cancer. The Gleason score is very important in the diagnosis of prostate cancer because it helps to predict the aggressiveness of the cancer, from low-risk (Gleason 6) to intermediate-risk (Gleason 7) and high-risk (Gleason 8 to 10). Here we explain what the Gleason Score is and how it is used with other important tests and investigations to determine your cancer stage and risk.
During a biopsy, your urologist (specialised surgeon) will collect a small sample of tissue from your prostate using an ultrasound-guided needle. The tissue samples are then sent to a pathologist (disease expert) to examine the samples under a microscope and assign a grade based on how the cells appear.
Gleason Grade Explained
When the pathologist looks at the biopsy sample, they use a grading system (1 to 5) which is based on how different patterns of cancerous cells look compared to healthy cells. Cells that are graded from 1 to 2 look more like healthy prostate cells. The more abnormal the cell, the higher the grade. Most prostate cancers have a Gleason grade of 3, 4 or 5.
Gleason Score: The Sum of Two Numbers
The Gleason score is the sum of the Gleason grades where the Primary grade is the most common cell pattern and the Secondary grade is the second most common cell pattern:
Primary Grade
+
Secondary Grade
=
Gleason Score
The Gleason score is the sum of the primary and secondary grade and ranges from 6 (low-risk) to a maximum of 10 (high-risk).
What Does Gleason Score 6 Mean?
Gleason score 6 suggests the prostate cancer is ‘low-grade’ or ‘low-risk’ as it is slow-growing and localised to the prostate (i.e. less likely to spread).
Gleason score 6 is reported as:
Gleason Score: 3 + 3 = 6
Gleason Score 3+3=6 is considered low-risk because the 1st number (primary) and 2nd number (secondary) is Grade 3. Grade 3 is considered only slightly cancerous and this is the most common cell pattern found in the tissue samples.
What does Gleason Score 7 mean?
Gleason score 7 indicates two very different levels of prostate cancer which differ in aggressiveness. Understandably, this can be confusing for men. It is therefore important to ask your doctor about both the primary and secondary grade numbers.
What is the difference between 3+4=7 and 4+3=7?
Gleason Score: 3 + 4 = 7
Gleason Score 3+4=7 is considered low to intermediate risk because the 1st number (primary) is Grade 3. Grade 3 is less aggressive than Grade 4, and is the most common cell pattern found in the biopsy sample.
Gleason Score: 4 + 3 = 7
Whereas, Gleason Score 4+3=7 is considered intermediate to high-risk because the 1st number (primary) is Grade 4. Grade 4 is the most common cell pattern found in the biopsy sample and is more aggressive than grade 3.
What does Gleason Score 8, 9 and 10 mean?
A Gleason score of 8 or higher means that the cancer is more aggressive and likely to spread to other parts of the body.
How is Gleason Score reported?
The biopsy results (called the pathology report) describe the Gleason score, and helps your doctor assess if you have prostate cancer and how aggressive it may be. Your doctor will also take into consideration where the biopsy samples were taken from within the prostate and whether cancer was found in just one or both sides of the prostate gland.
The following are examples of how the Gleason Score is described in doctor referral letters:
“Confirmed the presence of Gleason 7…within the right lobe of the prostate”
“Showed small volume Gleason 3+3 disease which I have recommended he proceed to…”
“Confirmed low grade Gleason 6…with staging studies showing no evidence of disease spread”
“Gleason 3+4=7 adenocarcinoma of the prostate…”
A new grading system called the ‘Grade Group’ has been put in place to help patients better understand their diagnosis as the Gleason Score can be difficult to interpret. The Grade Group ranges from 1 (least aggressive) to 5 (most aggressive). The table below outlines the Grade Group equivalent to the Gleason Score.
What is my prognosis?
It is not possible to predict the exact outcome of your prostate cancer as there are many factors that can influence how cancer cells grow and spread. Additional tests are used to determine the cancer stage and risk level including PSA blood tests, Digital Rectal Examinations (DRE), bone scans, MRI scans, CT scans etc. Your doctor will also take into consideration your age, overall health, medical and family history.
In general, the prognosis is better when prostate cancer is diagnosed as low-risk and confined to the prostate. According to the Cancer Council, prostate cancer has one of the highest five-year survival rates compared with other cancers.
Weighing up Treatment Options
A higher Gleason score generally means that prostate cancer will grow more quickly. However, remember that the score alone does not predict your prognosis (expected outcome). The Gleason score is only one consideration in establishing your risk of advancing cancer, and in weighing up your treatment options.
As a general guide, treatment options for men with Gleason score 6 (low-risk) prostate cancers include Active Surveillance (i.e. close monitoring), surgery, and radiation therapy. For Gleason score 7 (3+4=7 or 4+3=7), treatment options are often individualised because of the different severity levels (where Gleason score 3+4=7 is less severe). Gleason 8 and above will need treatment and treatment options might include surgery, radiotherapy, cryosurgery, hormone therapy, chemotherapy and immunotherapy.
There are pros and cons to consider in terms of your personal experience, potential side-effects and if additional treatment is needed. Ultimately, treatment decision-making depends on your own preferences and values, in consultation with expert advice from your treating doctor.
If you are reading this article before June 2020 and have recently been diagnosed with early-stage, low-risk prostate cancer, please consider joining our research trial www.navigateprostate.com.au to help navigate your treatment options.
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