What is a Gleason score?
When a doctor diagnoses prostate cancer, a biopsy of the cancer cells in the prostate will be done. Afterward, the Gleason score will be used to help explain the results.
The Gleason score is also used to determine how aggressive the cancer is and what the best course of treatment will be.
Contents of this article:
What is a Gleason score?
The Gleason score measures the progress of a cancer cell from normal to tumorous.
The Gleason score is a grading system devised in the 1960s by a pathologist called Donald Gleason.
Gleason worked out that cancerous cells fall into five differentt patterns, as they change from normal cells to tumorous cells. As a result, he determined they could be scored on a scale of 1 to 5.
The cells that score a 1 or 2 are considered to be low-grade tumor cells. These tend to look similar to normal cells.
Cells closest to 5 are considered high-grade. In comparison to the lower grade cells, they have mutated so much that they no longer look like normal cells.
How is the Gleason score worked out?
The Gleason score is determined by the results of the biopsy.
During a biopsy, the doctor takes tissue samples from different areas of the prostate. Several samples are taken, as cancer is not always present in all parts of the prostate.
After examining the samples under a microscope, the doctor finds the two areas that have the most cancer cells. The Gleason score is assigned to each of these areas, separately. Each is given a score of between 1 and 5. These are then added together to give a combined score, often referred to as the Gleason sum.
In most cases, the Gleason score is based on the two areas described above that make up most of the cancerous tissue.
However, there are some exceptions to the way scores are worked out.
When a biopsy sample has either a lot of high-grade cancer cells or shows three different types of grades, the Gleason score is modified to reflect how aggressive the cancer is deemed to be.
What do the results mean?
When a doctor tells a person what their Gleason score is, it will be between 2 and 10. Although it is not always the case, the higher the score, the more aggressive the cancer tends to be. Typically, lower scores indicate less aggressive cancers.
In most cases, scores range between 6 and 10. Biopsy samples that score 1 or 2 are not used very often because they are not usually the predominant areas of cancer.
A Gleason score of 6 is usually the lowest score possible. Prostate cancer with a score of 6 is described as well-differentiated or low-grade. This means the cancer is more likely to grow and spread slowly.
Scores between 8 and 10 are referred to as poorly differentiated or high-grade. In these cases, the cancer is likely to spread and grow quickly. Scores of 9 and 10 are twice as likely to grow and spread quickly as a score of 8.
In the case of a score of 7, the results could be one of two ways:
- 3 + 4 = 7
- 4 + 3 = 7
This distinction indicates how aggressive the tumor is. Scores of 3 + 4 typically have a good outlook. A score of 4 + 3 is more likely to grow and spread compared to the 3 + 4 score, but it is less likely to grow and spread than a score of 8.
In some cases, a person may receive multiple Gleason scores. This is because the grade may vary between samples within the same tumor or between two or more tumors. In these cases, the doctor is likely to use the highest score as the guide for treatment.
Other ways to measure prostate cancer
The Gleason scale is very important for doctors when they decide the best treatment options. However, there are some additional factors and groupings to assist them.
Some additional considerations include:
There are other factors which help determine the treatment plan for prostate cancer, including blood PSA levels and biopsy results.
- results of a rectal exam
- the blood PSA level of the individual
- the results of imaging tests
- the number of biopsy samples that contain cancer
- whether the cancer has spread beyond the prostate
- how much of each tissue sample is made up of cancer
- whether cancer is found on both sides of the prostate
More recently, researchers have determined additional groupings, called grade groups. These grade groups help address some of the problems with the Gleason system.
Currently, the lowest Gleason score that is given is a 6. In theory, however, the Gleason grades range from 2 to 10.
The lowest reported score of a 6 leads some people to think their cancer is in the middle of the grade scale. As a result, they are more likely to worry and to want treatment right away.
As described above, the Gleason scores are most often divided into only three groups: 6, 7, and 8-10.
These groupings are not entirely accurate since the Gleason score of 7 is made up of two grades, 3+4 and 4+3. Within this group, a 4+3 is a worse outlook than a 3+4.
Similarly, Gleason scores of 9 or 10 have a worse outlook than a Gleason score of 8, despite being in the same group.
The newer groupings are more understandable for the individual being treated and more accurate in terms of outlook and treatment.
The following is a breakdown of the new groups. A score of 1 is considered best and a score of 5 is considered worst.
- grade group 1 = Gleason 6 (or less)
- grade group 2 = Gleason 3+4=7
- grade group 3 = Gleason 4+3=7
- grade group 4 = Gleason 8
- grade group 5 = Gleason 9-10
How does a Gleason score affect treatment?
The Gleason score and similar groupings help a doctor give an outlook and treatment plan to an individual. This information and other factors are then used together to guide the treatment decisions.
For lower Gleason scores, treatment is likely to consist of:
- active surveillance, where someone’s age and overall health help determine when their cancer is treated
- radical prostatectomy surgery to remove the prostate
- radiation therapy
For higher Gleason scores and more advanced stages of cancer, treatment may consist of a combination of the following:
More advanced cancers may be treated with surgery, radiation therapy, or chemotherapy.
- radical prostatectomy
- brachytherapy only
- external beam radiation only
- brachytherapy and external beam radiation
- involvement in a clinical trial of newer treatments
- active surveillance
- hormone therapy
- surgery to treat symptoms of the cancer
Brachytherapy is a form of radiation therapy, where radiation is administered to the prostate by placing small radioactive seeds directly into the prostate. It is also referred to as internal radiation therapy.
External beam radiation involves the use of a machine that focuses beams of radiation onto the prostate from outside of the body.
People with prostate cancer will be able to discuss their treatment options with their doctor to decide the best ones for them.