Men's Health
Keeping score of prostate cancer
The Gleason score from a prostate biopsy reflects how the cancer is likely to behave.
- Reviewed by Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
Men who choose periodic screening for prostate cancer typically get a prostate-specific antigen (PSA) blood test. If the PSA level is abnormally high, men often need a biopsy. The biopsy not only confirms the presence of cancer, it also offers information on how it might grow and spread. This is done by creating a Gleason score from the biopsied samples.
"The Gleason score is the primary measurement to determine overall management of prostate cancer," says Dr. Marc B. Garnick, editor in chief of the Harvard Medical School Guide to Prostate Diseases. "It's important to understand how Gleason scores are calculated and what they can mean, as your ongoing treatment is often dictated by the results."
Getting to the core
The most common type of prostate biopsy is a transrectal biopsy. Here, the doctor passes a needle through the rectum and into the prostate to remove a small cylinder of tissue, called a core. Typically, 12 core samples are taken from different areas of the prostate. Your doctor also may take tissue samples from questionable areas identified during the DRE or possibly from a prostate MRI, if that was part of the pre-biopsy evaluation.
Another type of biopsy increasingly being used is a transperineal biopsy. This involves taking tissue core samples through the perineum, the skin between the rectum and scrotum. Studies have found they have fewer complications than transrectal ones. "Another advantage with transperineal biopsies is that samples are more easily obtained from the front of the prostate, where more aggressive cancer can appear," says Dr. Garnick.
A pathologist then examines the core samples. If the tissue shows prostate cancer, the pathologist grades the most prevalent type of cancer cell on a scale of 3 to 5. The higher the number, the more aggressive the cancer. The pathologist does the same for the second most prevalent type of cancer cell. The sum of the two grades is the Gleason score — for example, 3+3=6, 3+4=7, 4+3=7, 4+4=8, etc. Here's a breakdown of the scores:
- 6 suggests that cancer will grow slowly and is less likely to spread
- 7 indicates intermediate-grade cancer
- 8 to 10 (10 being the highest score) means high-grade, aggressive cancer.
Beyond the Gleason score
The final Gleason score does not provide some important nuances that affect therapy decisions. For instance, a Gleason score of 7 (4+3) is potentially more dangerous than a Gleason score of 7 (3+4). "The first number represents the common cell pattern," says Dr. Garnick. "Grade 4 cells are more abnormal and more likely to spread than grade 3 cells, so a 4+3 score is a higher-risk cancer than 3+4."
Another issue is that high-grade cancers are lumped together. "There can be big differences between Gleason 8, 9, and 10 cancers in terms of their aggressiveness," says Dr. Garnick. Gleason scores can also vary depending on where in the prostate the samples come from. "Cores might come from different areas of the same tumor or different tumors in the prostate," says Dr. Garnick. "Because the grade can vary within the same tumor or between different tumors, different cores can have different Gleason scores."
To help resolve these issues, the International Society of Urological Pathology created a new grading system. It divides Gleason scores into five grade groups:
- Grade Group 1 includes Gleason 3+3=6
- Grade Group 2 includes Gleason 3+4=7
- Grade Group 3 includes Gleason 4+3=7
- Grade Group 4 includes Gleason 4+4=8
- Grade Group 5 includes Gleason 4+5=9, 5+4=9, and 5+5=10.
How Gleason scores are used
Cancers with Gleason scores of 8, 9, or 10 usually require treatment, and your doctor will discuss which options are best for you. However, the necessity and timing of treatment for Gleason scores of 6 and 7 are not always clear-cut.
Most men with a Gleason 6 or 7 (3+4), which indicates low-risk cancer, can receive treatment or go on active surveillance, in which they monitor their PSA levels for changes. However, some men with low-risk cancer feel uneasy being so close to having more aggressive cancer and may wish to start earlier treatment.
Other findings from the biopsy are also used to calculate treatment options, such as the number of biopsy cores that contain cancer, the percentage of each core that contains cancer, and whether cancer was found on both sides of the prostate. "The Gleason score is an important marker in managing prostate cancer, but the number only provides information to help guide therapy decisions," says Dr. Garnick. "Ultimately, it's up to the doctor and patient to determine the next steps."
Image: © janiecbros/Getty Images
About the Author
Matthew Solan, Executive Editor, Harvard Men's Health Watch
About the Reviewer
Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
Disclaimer:
As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Please note the date of last review or update on all articles.
No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.
