Gleason score decoded: What it means, and how it helps guide prostate cancer treatment

If you’ve ever been diagnosed with prostate cancer, you were likely given a Gleason score. A Gleason score is part of the grading system we use for prostate cancer.

Here, I’ll break down how Gleason scores are determined, what each score means and how we use them to guide prostate cancer treatment. Don’t worry: you won’t need a calculator!    

What is a Gleason score?

After a prostate biopsy, a pathologist examines the tissue samples under a microscope. If cancer is found, the pathologist will look for patterns within the cancer cells and compare them with normal prostate cells.

As cancer cells mutate, they start to look less like healthy cells and more abnormal. How abnormal those cell patterns look determines the Gleason score.

The pathologist will identify the two patterns they see the most within the cancer cells and assign a grade to each.

Historically, grades were given on a scale of 1 to 5, with Grade 1 being cancer cells that looked a lot like normal cells and Grade 5 being cancer cells that looked the most abnormal. The two grades were then added together to determine the Gleason score.

Now that we have better pathology techniques, most pathologists no longer use Grades 1 and 2. The cell changes are so small that medical experts don’t think they actually rise to the level of being cancerous.

So, this means a Gleason score of 6 (3+3) or higher is considered prostate cancer.     

What does your Gleason score mean?

Your Gleason score can range from 6 to 10, with 6 being the least aggressive prostate cancer and 10 being the most aggressive. Here are all the potential scores:

• Gleason score 6: (3+3)
• Gleason score 7: (3+4 and 4+3)
• Gleason score 8: (3+5, 4+4 and 5+3)
• Gleason score 9: (4+5 and 5+4)
• Gleason score 10: (5+5)

It’s important to note that the first number in a Gleason score is the cell pattern that the pathologist sees the most in the sample. So, 4+3 is considered more aggressive than 3+4, even though they are both Gleason 7. Why? Because we know that there were more cells that looked abnormal in 4+3.

Prostate cancer Grade Groups

With so many number variations, Gleason scores can often be confusing for patients.

So, many doctors have adopted the Grade Group system to simplify grading prostate cancer. There are five Grade Groups (1 to 5), and they each correspond with Gleason scores.

• 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 or 10  

Grade Group 1 has the lowest risk of harm. It’s the least aggressive. That means the cancer grows slowly and is not likely to spread.

Grade Groups 2 and 3 are intermediate risk, with Grade Group 2 (3+4) being ‘favorable’ intermediate risk and Grade Group 3 (4+3) being ‘unfavorable’ intermediate risk.

Grade Groups 4 and 5 have the highest risk of harm. The cancer grows the fastest of all Grade Groups and is more likely to spread.

Some hospitals use only the Gleason score, while others use the Gleason score and Grade Group. UT MD Anderson uses both the Gleason score and Grade Groups.

What is a normal Gleason score?

Technically, a “normal” Gleason score would be not having one at all. A Gleason score means that you have prostate cancer, so there are abnormal cells present in the prostate.

That said, the most common type of prostate cancer is Gleason 6, or Grade Group 1. We see far more low-risk prostate cancers than we do high-risk prostate cancers.

How your Gleason score helps guide prostate cancer treatment

Your Gleason score helps guide prostate cancer treatment because the cancer’s grade can help doctors predict how quickly the cancer will grow. This allows them to select the best treatment options.

Your doctor will also consider other factors, such as prostate-specific antigen (PSA) levels and your overall health when developing a treatment plan.

Prostate cancer in general is a slow-growing cancer compared to other types of cancer. So, Gleason 6 prostate cancer is a slow-growing version of a slow-growing cancer.

Treatment for low-risk prostate cancer

Gleason 6 prostate cancer is not life-threatening. We typically recommend active surveillance, where we’ll closely monitor the cancer for any changes. You’ll have regular follow-up visits with your doctor that may include prostate-specific antigen (PSA) tests, digital rectal exams, MRIs or repeat prostate biopsies. If your doctor notices any concerning changes, they may recommend that you begin treatment, such as surgery or radiation therapy.    

Treatment for intermediate-risk prostate cancer

Gleason 7 is somewhat of a middle ground. That’s because there are several treatment options. Intermediate-risk prostate cancer can often be cured with treatment.

If the cancer is a 3+4, there’s a ‘favorable’ intermediate risk. Your doctor might recommend any of the following:

• Active surveillance
• Treatment with surgery or radiation
• Focal therapy, such as cryoablation or high-intensity forced ultrasound (HIFU)

Patients can have a hard time understanding 3+4 because they aren’t sure which treatment option to choose. Be sure to talk to your doctor about any concerns or questions you have. That way, you can work together to find the best treatment plan for you.

Treatment is almost always recommended for 4+3 prostate cancer as there is an ‘unfavorable’ intermediate risk. But you’ll never need to be treated right away for prostate cancer that is localized, or just located within the prostate. There’s often a window of several months between diagnosis and when you begin treatment. This means you can take the time to have meaningful conversations with your loved ones and care team to determine the best path forward.

Treatment for high-risk prostate cancer

Gleason 8, 9 and 10 are the fastest growing types of prostate cancer. I usually tell patients it’s similar to having a fast turtle. Yes, it is fast, but fast for a turtle. It’s not a cheetah. So, Gleason 8, 9 and 10 are fast-growing versions of a slow-growing cancer.

Treatment is almost always recommended for these types of prostate cancer because they have the highest chance of becoming metastatic, which is when the cancer spreads outside of the prostate to other parts of the body. This is also known as stage IV prostate cancer.

Treatment for metastatic prostate cancer may include systemic therapies like hormone therapy, chemotherapy or radiation therapy. While metastatic prostate cancer is not curable, it is treatable. There are several clinical trials studying how new drugs and drug combinations can help treat metastatic prostate cancer.   

What else should men know about the Gleason score?

Pathologists are the ones who derive the Gleason score from prostate tissue samples. So, whenever someone comes to UT MD Anderson after having a prostate biopsy done elsewhere, we always strongly encourage them to have their pathology report reviewed by our pathologists.

At UT MD Anderson, we have subspecialist genitourinary pathologists who only look at prostate biopsies, day in and day out. They provide a great level of detail in the pathology reports.

For example, for Gleason 7, our pathologists will tell us what percentage is pattern 4. A 3+4 means that there is a majority of pattern 3. But if there’s 99% pattern 3 and just 1% pattern 4, that’s very different than if there’s 60% pattern 3 and 40% pattern 4.

This is helpful for doctors to know about Gleason 7 because if there’s just a very small percentage of pattern 4, we could potentially just do active surveillance. But if it’s just less than half – say, 45% – we may recommend treatment.

Trying to understand how we grade prostate cancer can be confusing at first. But we’re here to help you. Let your care team know if you have any questions about your Gleason score or your prostate cancer diagnosis.   

Lisly Chéry, M.D., is a urologic oncologist at UT MD Anderson in Sugar Land.

Request an appointment at UT MD Anderson online or call 1-877-632-6789.