The Gleason score functions as a measurement of the aggressiveness of prostate cancer.
Aggressiveness is the medical term used to describe the likelihood of the tumor spreading outside the prostate gland.
You will get receive a Gleason score after having a prostate biopsy.
Your doctor may recommend a biopsy if your PSA level rises or there is cause for concern after your annual checkup or a digital rectal exam (DRE), such as an increase in prostate volume or nodules and legions.
Modern biopsies are typically performed using transrectal ultrasound guidance, whereas older methods were unassisted; these are called random needle biopsies. By using ultrasound guidance, the doctor can take a more accurate and evenly distributed sample from the prostate gland.
Normally twelve separate cores (samples of prostate tissue) are extracted. After which they are sent to a laboratory.
At the laboratory, a pathologist examines the tissue cores using a microscope to see if they contain cancerous cells.
If the pathologist finds evidence of prostate cancer cells in the sample, he will attempt to match your samples with Gleason guidelines. These guidelines are scored between one and five.
Your Gleason score is made up of two of these guidelines, and therefore, your score can range from two to ten.
It is then put into a pathology report sometimes called a biopsy report, that will be sent to your primary care physician.
The needle biopsy required for a Gleason score is an invasive surgical, diagnostic procedure, and many men have concerns about its safety and accuracy.
You can find out more about needle biopsies and other less invasive prostate cancer diagnostic procedures here.
How is a Gleason score calculated?
The way a Gleason score is calculated is by comparing your biopsy samples to guideline samples. Each guideline shows a pattern of prostate cancer cell growth, and each guideline has been assigned a score between one and five.
These patterns relate to the tumor’s rate of growth, which, in turn, reveal their aggressiveness.
When your pathologist checks your biopsy samples, they examine your prostate cells under the microscope and will look at the different patterns.
The most common pattern of cancer cell growth is assigned a score, as is the second most common pattern of cancer cell growth. When these two scores are added together, the total is called the Gleason score.
Here is an example:
A pathologist looks at a sample and finds that the most common pattern matches the guideline pattern for Gleason 3 and the second most common pattern matches the pattern for Gleason Gleason 4.
This means that the cancer is primarily made up of cells that fit pattern 3 and to lesser extent cells that match pattern 4.
This would result in a Gleason Score of 7, which will appear on your test results as Gleason Score 3+4 = 7.
Here is a second example:
The most common pattern matches the guideline for Gleason 5 and the second most common pattern matches the guideline pattern for Gleason 4. This would mean that the cancer is primarily made up of cells that fit pattern 5 and to lesser extent cells that match pattern 4.
This would result in a Gleason Score of 9, which will appear on your test results as Gleason Score 5+4 = 9.
The order of the individual Gleason scores is, therefore, significant since the first score is the most common pattern of prostate cancer cells. This means that a Gleason score 4+3=7 tumor is more aggressive and faster-growing than a 3+4=7 tumor.
The Higher the Gleason score, the more advanced and aggressive prostate cancer. These high-grade tumors are more likely than low-grade tumors metastasize, (spread outside of the prostate).
It is worth noting that patterns 1 and 2 are rarely seen in a Gleason score. There are two reasons for this. Firstly it is because they are almost impossible to distinguish these types of cells from normal prostate cells.
And secondly, it is because men who would have such low scores would likely be largely asymptomatic and therefore it is unlikely that a biopsy would be done. In fact, a PSA test may not even show anything wrong at this point.
Because patterns 1 and 2 are rarely seen, the lowest Gleason score of cancer found on a prostate biopsy is 6.
The highest a Gleason score can be is 10. Although anything above a Gleason score of 7 (4+3) is thought to be a high Gleason score and anything below a Gleason score of 7 (3+4) is believed to be indicative of low-grade cancer.
Is the Gleason score accurate?
Multiple studies have found that Gleason scores are relatively inaccurate and pathologists have a tendency to overestimate the Gleason score of biopsy samples.
A 2001 analysis of 1,031 patients who had a biopsy and then opted for a radical prostatectomy revealed that in 41.7% of cases, the Gleason score was inaccurate.
Prostate glands were examined after they had been surgically removed via a radical prostatectomy. In cases where the pathologist assigned a Gleason score lower than 7, they were wrong 45.2% of the time.
In cases where they had assigned a Gleason score of 7 they were wrong 33.2% of the time and in cases where they had assigned a Gleason score greater than 7 they were wrong 52.% of the time.
Another study conducted on 464 men in 2008 found that the biopsy results (Gleason score), and the examinations of the prostate after a radical prostatectomy only agreed in approximately 57% of cases.
This study from the International Journal of Radiation Oncology Biology Physics found that pathologists underestimated Gleason scores in 29% of cases and overestimated scores in 14% of cases.
Since 2015 a new 5 tiered grading system has been being tested as a potential replacement to the Gleason score. It has already been accepted by the World Health Organization and the International Society of Urological Pathology as a viable diagnostic.
This new condensed grading system was developed at Johns Hopkins University investigators and is being trialed across the world in parallel with the Gleason score system to see if it increases accuracy.
The new condensed system is a far more straightforward grading method and should increase pathologist accuracy.
However, no studies yet confirm this, so it is unclear whether or not the simplification in possible scores is to the patient’s benefit or as some critics have said for the physician’s benefit.
The new grading system still relies on a biopsy, and even though new auxiliary procedures increase the sensibility and specificity of biopsy results, the consequences of biopsies are still the same, and we recommend a full battery of non-invasive prostate cancer diagnostics before opting for any treatment
The high rate of inaccuracy in Gleason scores and its invasive nature is why we recommend a full battery of non-invasive prostate cancer diagnostics before opting for any treatment.
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How can a Gleason score affect prostate cancer treatment?
The Gleason score is just one of the diagnostics that your urologist and primary care physician will rely on to help determine your best treatment option.
In general, your physician will depend on a number of diagnostics before advising you, as to your best course of action.
These can include Multiparametric MRI scans, Ultrasound scans, and Biopsy results like the Gleason score.
Your diagnostic tests, including your Gleason score results, will allow your physician to calculate the stage of your cancer. The stage of your cancer is what will primarily affect what treatment your physician will recommend.
The full article on the different stages of prostate cancer and how they affect your treatment options here.
As a general guideline, though, The higher your Gleason score, the more likely it is that your doctor will recommend a more invasive treatment option.
When it comes to Gleason scores of 6, (3+3=6) and Gleason scores of (3+4=7), many oncologists do not feel that treatment is beneficial.
Jonathan Oppenheimer, MD, was one of the first pathologists to study Gleason 6 tumors. He has argued that the medical community needs to stop using the word “cancer” when referring to tumors that have Gleason scores of 6.
He argues that A Gleason 6 tumor is so close to benign and that the use of the word cancer unnecessarily increases the risk that the patient will opt for unnecessary and dangerous treatment options being undertaken.
Another notable doctor in the field, Dr. Bert Vorstman, MD, MS, FAAP, FRACS, FACS noted that “Since the Gleason 6 lacks the hallmarks of cancer, it is pseudo cancer, not a health risk; does not progress to become a health risk; needs no detection; and needs no treatment”.
Longitudinal studies demonstrate that true Gleason 6 grade tumors never demonstrate metastatic propensity.
Meaning that prostate cancer is unlikely to be associated with an increase in mortality risk, and will not cause a worsening of symptoms.
Proponents argue that this evidence means that any invasive treatment is a potential overaction by the doctor or patient, and maybe worse than the condition itself.
This is especially noteworthy given that a Gleason score of 6 is the most common score for prostate cancers in the US.
If you have a Gleason 6 tumor, then you may wish to consult your primary care physician as to whether or not a treatment or active surveillance would be a preferable option.
In the case of a Gleason score of 7, A study of prostate cancer patients that was published in 2006 noted that in 47% of cases A Gleason score of 7, (4+3=7) turned out to be a less aggressive prostate cancer which should have warranted a lower PSA score…
“Of the patients with Gleason pattern 3 + 4 tumors on biopsy, 24% were upgraded to primary pattern 4 or more on final pathologic analysis. Of the patients with Gleason pattern 4 + 3 tumors on biopsy, 47% were downgraded to primary pattern 3 or less on final pathologic analysis.”
Even if you have been diagnosed with a Gleason 7 tumor, it is possible to still opt for a watchful waiting or active surveillance approach.
More aggressive prostate cancers, which are more likely to, or have already metastasized, may require more serious treatment options. In the United States and Europe, the most common treatment options are:
- Radical Prostatectomy, (the full removal of the prostate gland via surgical means).
- External Beam Radiation Therapy, (often either photon beam or proton beam treatment, you can read about the differences between the various types of radiation therapy in this article here)
- Brachytherapy, (the implantation of radioactive seeds into the prostate cancer)
- Androgen Deprivation Therapy, (a hormone therapy designed to starve the prostate gland of Androgen hormones that are associated with prostate cancer cell growth)
- Cryotherapy, (using cold fluid or gas to kill the prostate cancer cells)
- High Intensity Focused Ultrasound (HIFU)
For more information about the different treatment options, you should read our in-depth prostate cancer treatment report. The report examines the differences in quality of life outcomes at 2,5 and 10 years after treatment.
Understanding your Gleason score
What does a Gleason grade of 6 mean?
A Gleason score 6 tumor means that the cancer cells look very similar to healthy prostate gland tissue. This suggests that the cancer is going to grow slowly.
As discussed above, a Gleason score of 6 is the lowest and least threatening Gleason score you can have. With this diagnosis, you may want to consider active surveillance or non-invasive treatments.
What does a Gleason grade of 7 mean?
A Gleason score 7 tumor indicates a moderate risk of aggressive cancer. However, as explained above, a Gleason 7 can be either a 3+4=7 or a 4+3=7 tumor.
The former is far less concerning. It is also worth noting that in 47% of cases where a patient who had a 4+3= Gleason 7 tumor opted for surgical removal of the prostate, the cancer was downgraded to a Gleason 6 or lower.
What does a Gleason grade of 8 mean?
A Gleason score 8 tumor indicates aggressive cancer that is more likely to spread beyond the prostate.
The individual cancer cells are often referred to as poorly differentiated, and the cancer is often described as high grade or advanced prostate cancer.
What does a Gleason grade of 9 mean?
A Gleason score 9 tumor indicates highly aggressive cancer that is highly likely to metastasize beyond the prostate.
What does a Gleason grade of 10 mean?
A Gleason score of 10 tumor is the most aggressive and fastest-growing form of prostate cancer. It is highly likely that it will metastasize beyond the prostate gland and spread to nearby lymph nodes and systems.
Does my Gleason score indicate how likely recurrence or remission is?
Several clinical factors contribute to the overall risk of relapse after treatment. Gleason score is one potential indicator of your chances of biochemical recurrence.
Keep in mind that these are rough estimates and many other factors can decrease or increase your risk of failed remission, even if you have had the prostate surgically removed via a prostatectomy.
What is the new condensed grading system?
The new condensed prostate cancer grading system is currently being tested as a replacement for the current Gleason grading system.
The new condensed system was created to provide a simplified system that focuses on better segmenting and differentiating the lower grade, (more common) prostate cancers.
The hope is that this will help to reduce unnecessary treatment of less aggressive prostate cancer. The new grading system subdivides prostate cancer into five categories, rather than the potential 25 categories of the Gleason score. The condensed system relies on pathological characteristics.