What a High Gleason Score May Mean for Prostate Cancer

A Gleason score is one of the most important factors doctors use to evaluate prostate cancer. It is determined by examining prostate tissue collected during a biopsy and grading how abnormal the cancer cells look under a microscope. Rather than measuring the size of the tumor, the Gleason score estimates how likely the cancer is to grow and spread. Today, the score is often reported alongside the Grade Group system to help patients better understand the aggressiveness of their cancer and guide treatment decisions.

A high Gleason score generally means the prostate cancer cells appear more abnormal and may behave more aggressively than cancers with lower scores. However, the Gleason score is only one part of the overall picture. Doctors also consider the prostate-specific antigen (PSA) level, imaging results, tumor stage, biopsy findings, and your overall health when recommending treatment. This article explains what a high Gleason score may mean, how it influences prognosis, and the treatment options that may be considered for different stages of prostate cancer.

What Does a High Gleason Score Mean for Prostate Cancer Aggressiveness?

A high Gleason score means that the cancer cells found in a prostate biopsy appear highly abnormal and disorganized, indicating an aggressive form of cancer with a strong potential to grow and spread quickly. To understand better, the Gleason scoring system is the most common method used by pathologists to grade prostate cancer based on its microscopic appearance, which directly correlates with its biological aggressiveness.

The Pathological Microscopic Grading Scale

When a pathologist examines tissue samples under a microscope, they assign a structural grade from 1 to 5 based on how much the cancer cells have mutated away from normal, healthy prostate glands.

Grade 3 represents a low-grade, well-differentiated pattern. The cancer cells still form distinct, separate, and recognizable glandular circles. Although these glands are smaller and more crowded than healthy ones, they maintain an organized structure. The cells themselves are uniform, which reflects slower growth and a much lower likelihood of spreading outside the prostate. This is the most common low-grade pattern found in a typical gleason score 6.

Grade 4 represents a high-grade, poorly-differentiated pattern. The individual glands begin to lose their borders and fuse together. They form irregular, sieve-like sheets or poorly defined clusters of cells. This breakdown of normal tissue architecture is a direct biological sign that the cancer is becoming more aggressive, invasive, and harder to contain.

Grade 5 represents a high-grade, undifferentiated pattern. This is the most aggressive pattern possible. There is a complete lack of any glandular formation. The cancer cells grow in solid sheets, dense cords, or as single, disorganized cells moving through the surrounding tissue. The cells vary significantly in size and shape, showing high genetic instability and a strong ability to invade blood vessels and lymph nodes to spread throughout the body.

Note: Grades 1 and 2 look almost identical to normal, non-cancerous prostate cells and are rarely used in modern biopsy reports.

Calculating the Combined Gleason Score

The final gleason score prostate cancer calculation is a combined sum of two numbers. The pathologist evaluates the tissue samples and identifies the two most common growth patterns using a specific formula: Primary Pattern Grade plus Secondary Pattern Grade equals the Total Gleason Score.

The Primary Pattern Grade represents the most common, widespread cell architecture visible across the biopsy samples. It is always listed as the first number in the score.

The Secondary Pattern Grade represents the next most common cell layout found in the tissue samples. It is always listed as the second number in the score.

Because the dominant pattern is listed first, the order of the numbers affects your overall prognosis and risk level. For example, a gleason score 7 written as 4 + 3 = 7 means Grade 4 is the dominant tissue type, making it inherently more aggressive than a 3 + 4 = 7 cancer, where the less aggressive Grade 3 pattern dominates. The final combined score ranges from 6 to 10.

High-Risk Gleason Classifications (Scores 8 to 10)

Combined scores of 8, 9, and 10 are universally classified as high-risk, high-grade prostate cancers. These scores indicate an aggressive disease that grows quickly and has a strong potential to spread if not treated promptly.

Gleason Score 8 is also classified as Grade Group 4. This score is most commonly a 4 + 4 = 8, meaning both the dominant and secondary patterns consist of aggressive, poorly-differentiated cells. Less commonly, it can present as 3 + 5 = 8 or 5 + 3 = 8. Any score of 8 carries a high risk, but a score with a primary pattern of 5 ($5 + 3$) is considered more aggressive because the most severe cell pattern is the dominant one.

Gleason Score 9 is classified as Grade Group 5. This score is made up of either 4 + 5 = 9 or 5 + 4 = 9. The presence of a Grade 5 pattern indicates a very high-risk cancer. These tumors are highly disorganized and have a strong tendency to invade nearby structures—such as the seminal vesicles, bladder neck, or rectum—and spread to distant sites like the bones.

Gleason Score 10 is also classified as Grade Group 5. This is the highest possible score, consisting of a 5 + 5 = 10. It signifies that the entire tumor sample is made up of the most aggressive, undifferentiated cancer cells. A Gleason score of 10 carries the most unfavorable prognosis, with the highest likelihood of rapid progression and resistance to localized treatments, requiring an immediate and intensive multi-modality treatment plan.

Overview of the Gleason Grading Framework

• Gleason 6 Prostate Cancer: Formally written as a prostate gleason score 6 (3 + 3). It represents well-differentiated, slow-growing cells and carries an exceptionally low risk of spreading, making it a strong candidate for active surveillance rather than immediate surgery.

• Gleason Score 7: An intermediate-grade cancer (3 + 4 or 4 + 3) where the order of the numbers indicates whether low-grade or high-grade tissue is dominant.

• High Gleason Scores (8-10): High-risk, poorly-differentiated tumors that have lost their normal structure, tend to grow quickly, and require prompt medical intervention.

The Typical Prognosis with a High Gleason Score

The typical prognosis with a high Gleason score (8-10) is more serious than with lower scores, indicating a higher risk of cancer progression, recurrence after treatment, and metastasis. However, it is crucial to understand that a high Gleason score is not a definitive sentence; it is a critical risk factor that guides the need for aggressive treatment, and many men are cured despite having high-grade disease.

Long-Term Survival and Recurrence Trends

When reviewing prostate biopsy results, receiving a high gleason score (8 to 10) indicates a serious medical situation. However, it is important to remember that these scores are risk factors used to guide aggressive treatment, not a definitive final sentence.

For men diagnosed with high-risk, localized prostate cancer, the 5-year relative survival rate remains very high, often exceeding 95%. This high short-term survival rate occurs because initial treatments are highly effective at controlling the disease.

However, looking further ahead reveals a more challenging timeline. The 10- and 15-year cancer-specific survival rates drop for high-grade tumors. Large clinical studies show that the 10-year prostate cancer mortality rate for men with scores of 8 to 10 ranges from 15% to 35%, depending on their baseline PSA levels and stage of disease. For comparison, the 10-year mortality rate for a low-grade prostate gleason score 6 is less than 1%.

This long-term shift is driven by two main clinical factors:

• Biochemical Recurrence (BCR): This occurs when your Prostate-Specific Antigen (PSA) level begins to rise after initial treatment, signaling that hidden cancer cells have returned. For men who undergo a radical prostatectomy, the 5-year risk of experiencing a PSA relapse with a high-grade cancer ranges from 40% to 60%.

• Metastatic Potential: High-grade cancer cells are naturally more capable of breaking away from the main tumor site. The risk of these cells spreading to distant parts of the body, such as the bones or pelvic lymph nodes, within 5 to 10 years after treatment is significantly higher than for intermediate-grade tumors.

The Path to a Cure for High-Risk Disease

It is absolutely possible to be cured of prostate cancer even with an aggressive, high-risk score, especially when the disease is caught while it is still confined to the prostate gland. Modern advancements in oncology are designed to aggressively target these high-risk profiles to achieve long-term remission.

[Early Local Detection] ──► Multimodal Attack (Surgery + Radiation) ──► Complete Eradication

Definitive Local Treatments: The foundation of curative care relies on completely removing or destroying the cancer cells before they can travel outside the pelvis. This is typically accomplished through an aggressive radical prostatectomy—often paired with an extended pelvic lymph node dissection to remove nearby nodes—or high-dose external beam radiation therapy.

Multimodal Treatment Plans: Because high-grade cells carry a risk of early microscopic spread, oncologists rarely rely on a single treatment method. Instead, they use a multimodal approach to attack the cancer from multiple angles. The most common combination involves pairing advanced radiation therapy with long-term androgen deprivation therapy (ADT), or hormone therapy. This combination deprives the cancer cells of the testosterone they need to grow, which significantly lowers recurrence rates and improves long-term survival.

The Power of Early Intervention: The sooner an aggressive tumor is diagnosed, the more likely it is to be trapped within the prostate wall. Catching the disease early allows your medical team to use these curative therapies before the cancer can spread to the bones, which greatly increases your chances of a successful, long-term recovery.

Comparing Outcomes: Scores 8, 9, and 10

While scores of 8, 9, and 10 are all grouped together as high-risk, they represent a spectrum of aggressiveness. Your exact position on this scale alters your prognosis and helps your medical team fine-tune your treatment plan.

                         [High-Risk Severity Spectrum]
                                       │
     ┌─────────────────────────────────┴─────────────────────────────────┐
     ▼                                                                   ▼
[Gleason Score 8]                   [Gleason Score 9]                   [Gleason Score 10]
 ├── Grade Group 4                   ├── Grade Group 5                   ├── Grade Group 5
 ├── Absence of pattern 5 tissue     ├── Inclusion of pattern 5 tissue   ├── Entirely pattern 5 tissue
 └── 10-year spread risk of 20-30%   └── 10-year spread risk of 35-50%   └── Highest rate of structural failure

Gleason Score 8 (Grade Group 4)

Typically presenting as a 4 + 4 = 8, this score indicates that the tumor is entirely made up of poorly-differentiated Grade 4 tissue, without the most severe Grade 5 cells. Because it lacks Grade 5 tissue, it behaves the least aggressively within the high-risk group. The 10-year risk of developing distant metastases after surgery for a score of 8 is estimated to be around 20% to 30%.

Gleason Score 9 (Grade Group 5)

A score of 9 consists of either a 4 + 5 = 9 or a 5 + 4 = 9 pattern. Introducing a Grade 5 component marks a major change in how the disease behaves. This indicates a highly disorganized cell structure that is more likely to have already spread micro-scopically by the time you are diagnosed. Consequently, patients with a score of 9 face a significantly higher risk of a rising PSA and cancer-specific mortality, with the 10-year risk of distant spread rising to between 35% and 50%.

Gleason Score 10 (Grade Group 5)

This is the highest and most aggressive score possible, consisting of a 5 + 5 = 10. It means the entire tumor sample is made up of the most disorganized, rapidly dividing Grade 5 cells. Because there are no less-aggressive cells to balance the tumor, a score of 10 carries the highest risk of spreading into the seminal vesicles, invading nearby lymph nodes, or leaving cancerous cells behind at the surgical margins. These tumors are the most likely to resist standard localized therapies, meaning patients often require clinical trials or immediate, aggressive systemic treatments. In some clinical tracking groups, the 10-year prostate cancer-specific mortality rate can reach or exceed 50%.

The Standard Treatment Paths for a High Gleason Score?

The standard treatment paths for a high Gleason score involve aggressive, definitive therapies aimed at cure, most commonly radical prostatectomy or external beam radiation therapy combined with long-term hormone therapy. Due to the high risk of cancer spread, treatment is initiated promptly and often involves a combination of modalities to address both the localized tumor and potential microscopic disease that may have escaped the prostate.

Primary Curative Approaches for Localized High-Risk Disease

When a high gleason score (8, 9, or 10) is confirmed, the medical team will pivot immediately toward aggressive, curative-intent therapies. Because these high-grade cells carry an inherent risk of early microscopic spread, treatment begins promptly.

The two primary standard-of-care treatments for localized high-risk prostate cancer are radical prostatectomy and external beam radiation therapy paired with long-term hormone therapy.

Radical Prostatectomy with Pelvic Lymph Node Dissection

This is a major surgical option designed to physically remove all cancerous tissue from the pelvis. The urologist removes the entire prostate gland, the attached seminal vesicles, and performs an extended pelvic lymph node dissection.

Removing and analyzing these surrounding lymph nodes is crucial because it allows pathologists to see if individual cancer cells have broken away from the main tumor.

Surgery provides definitive pathological staging, revealing whether the malignancy has breached the prostate capsule or invaded the seminal vesicles. This information is critical for determining if further post-operative treatments are necessary. The procedure can be performed via traditional open surgery or through minimally invasive robotic-assisted laparoscopy.

External Beam Radiation Therapy paired with Androgen Deprivation Therapy

This non-surgical approach uses precisely targeted high-energy X-rays or protons to destroy cancer cells within the prostate and surrounding pelvic tissues. For a high gleason score prostate cancer, radiation is almost never used alone. Instead, it is paired with Androgen Deprivation Therapy (ADT), or hormone therapy.

Prostate cancer cells rely on male hormones, primarily testosterone, to grow and multiply. ADT lowers these hormone levels, which weakens the cancer cells and makes them significantly more vulnerable to the cell-killing effects of radiation.

For high-risk disease, the standard of care requires a long-term course of ADT—typically lasting between 18 and 36 months—which begins before radiation starts and continues long after it concludes to suppress any hidden microscopic cells.

Multimodal Treatment Combinations to Improve Outcomes

Because high-grade prostate cancers have a tendency to recur or spread, combining multiple treatment methods is often the most effective strategy to ensure a long-term cure. This combined approach targets the cancer from several angles at once.

Surgery followed by Adjuvant Radiation or Hormone Therapy

If a patient undergoes a radical prostatectomy and their final post-operative pathology report reveals high-risk features, further treatment may be needed. These features include finding cancer cells at the very edge of the removed tissue (positive surgical margins), invasion into the seminal vesicles, or extension outside the prostate wall.

In these situations, a doctor may recommend adjuvant radiation therapy to the prostate bed to eliminate any remaining microscopic cells and reduce the risk of a local recurrence. If the surgery reveals that the cancer has traveled into the pelvic lymph nodes, long-term ADT may also be added to treat any potential systemic disease.

Advanced Treatment Intensification

For patients with very high-risk profiles, cancer care paradigms continue to advance. Oncologists are increasingly using a strategy called treatment intensification.

This approach adds newer, highly potent hormone therapies—such as abiraterone or enzalutamide—to the standard combination of baseline ADT and radiation. Large-scale clinical trials have shown that blocking cancer growth signals more aggressively from the start significantly reduces the risk of metastasis and improves long-term survival for high-risk patients.

Why Active Surveillance is Eliminated for High Gleason Scores

Active surveillance is a management strategy where slow-growing, low-risk cancers are carefully monitored with regular blood tests and biopsies, delaying treatment until the disease shows signs of progressing. While this is an excellent path for low-grade tumors, it is never a safe or appropriate option for a high Gleason score.

                  [Contraindication Framework]
                               │
     ┌─────────────────────────┴─────────────────────────┐
     ▼                                                   ▼
[The Aggressive Biology Window]                     [The Shift in Clinical Goals]
 ├── Rapid cellular duplication & tissue invasion    ├── Delaying care allows localized tumors
 └── Early systemic escape to pelvic bones               to transform into incurable systemic disease

The reasons why active surveillance cannot be used for high-grade tumors are absolute and based entirely on how these cells behave:

High Risk of Rapid Metastasis: High-grade cancer cells grow quickly and are highly invasive. Delaying definitive treatment gives the tumor a critical window of opportunity to escape the prostate capsule and spread to distant sites like the lymph nodes and bones. Once prostate cancer metastasizes, it is no longer curable, and the goal of treatment shifts from completely curing the disease to simply controlling it.

Unacceptable Risk of Mortality: Leaving an aggressive, high-risk cancer untreated or unmanaged leads to poor outcomes. The natural course of an unmanaged Gleason 8 to 10 tumor carries an unacceptably high risk of developing advanced, symptomatic metastatic disease, which ultimately decreases long-term survival.

Universal Clinical Consensus: Every major international urological and oncological organization—including the American Urological Association (AUA), the National Comprehensive Cancer Network (NCCN), and the European Association of Urology (EAU)—explicitly states that active surveillance is contraindicated for high-risk disease. The universal medical consensus requires immediate, proactive intervention.

What Other Factors Influence Your Prostate Cancer Diagnosis and Treatment?

Beyond the Gleason score, your diagnosis and treatment are influenced by a combination of factors including the modern Grade Group system, Prostate-Specific Antigen levels, the cancer’s clinical stage, advanced genomic testing, and insights from an expert second opinion. Furthermore, these elements work together to create a comprehensive risk profile, allowing for a more personalized and effective treatment strategy than relying on a single pathological score.

A high Gleason score is a significant indicator of aggressive cancer, but it is the interplay of these additional data points that truly defines the cancer’s character and guides the most appropriate course of action, from active surveillance to multi-modal therapies. Each component provides a unique piece of the diagnostic puzzle, ensuring that decisions are based on a holistic understanding of the disease’s potential behavior.

The Modern Grade Group System

To simplify and clarify the prognostic information provided by the traditional gleason score, the International Society of Urological Pathology (ISUP) introduced the Grade Group system. While the classic prostate gleason score 6 or higher has been the standard for decades, its non-continuous scale can sometimes sound confusing or alarmingly high to patients.

The Grade Group system addresses this by stratifying prostate biopsy results into five distinct, intuitive groups, running from 1 (least aggressive) to 5 (most aggressive). This gives a much clearer picture of how the cancer cells are likely to behave:

• Grade Group 1: Corresponds to a gleason score 6 (3+3). This represents a low-grade cancer that is highly organized, slow-growing, and carries an exceptionally low risk of spreading outside the prostate gland.

• Grade Group 2: Corresponds to a gleason score 7 (3+4). The tissue contains a mix of cells, but the less aggressive Grade 3 pattern is still dominant. This points to a favorable, intermediate-risk prognosis.

• Grade Group 3: Corresponds to a gleason score 7 (4+3). This indicates that the more aggressive Grade 4 pattern is now dominant across the tissue samples. This signals a less favorable intermediate-risk profile that requires more proactive management.

• Grade Group 4: Corresponds to a Gleason score of 8 (4+4, 3+5, or 5+3). These are high-risk cancers with significant potential for rapid, aggressive growth and tissue invasion.

• Grade Group 5: Corresponds to Gleason scores of 9 and 10. This is the highest-risk category, representing poorly differentiated, highly chaotic cancers with a high probability of early metastasis.

Integrating PSA Levels and Clinical Staging (TNM)

A high gleason score prostate cancer diagnosis does not exist in a vacuum. To build a complete and accurate risk profile, your medical team must combine your microscopic tumor grade with two other essential data points: your Prostate-Specific Antigen (PSA) level and your clinical TNM stage.

The PSA level is measured through a simple blood test. Because this protein is produced by prostate cells, a high or rapidly rising PSA level often indicates a larger, more active, or fast-growing tumor.

The TNM staging system provides a standardized way to map out the cancer’s physical footprint:

• T (Tumor): Describes the physical size of the primary tumor and notes whether it has breached the outer capsule of the prostate gland.

• N (Nodes): Identifies whether individual cancer cells have traveled into nearby pelvic lymph nodes.

• M (Metastasis): Confirms whether the cancer has spread to distant parts of the body, such as the bones.

The Power of Combined Data

When these three components are analyzed together, they create a highly accurate risk map. For example, a patient with a high Gleason score of 9, a high PSA level (such as over 20 ng/mL), and a T3 clinical stage (meaning the tumor has grown outside the prostate wall) has a serious condition that requires immediate, multi-modality treatments like surgery combined with radiation and hormone therapy.

Conversely, if a patient has a high-risk Gleason score of 8 but a low, stable PSA level and a tumor completely confined to the prostate (T1 or T2), their overall risk profile is less severe. This distinction allows doctors to fine-tune the timing, sequence, and intensity of the treatments they recommend.

Advanced Genomic Testing: Looking Inside the Tumor

While looking at a tumor’s architecture under a microscope tells us a lot, advanced genomic testing provides a deeper look into the biological engine of the cancer. These tests analyze the expression and activity of specific genes within the tissue samples collected during your biopsy.

This genetic information reveals how aggressive the tumor is on a molecular level, offering prognostic insights that are completely independent of your PSA or Gleason score. Prominent examples of these molecular tests include Decipher, Prolaris, Oncotype DX Prostate, and ProMark.

These sophisticated tests provide highly personalized, actionable information that can significantly shape your treatment plan:

Predicting Metastasis Risk: Tests like the Decipher classifier evaluate genetic markers to calculate the exact probability of the cancer spreading to other organs over the next five to ten years. A high genomic risk score in a patient with an intermediate- or high-grade tumor often prompts an oncologist to recommend a more intensive, multi-modal treatment plan right from the start.

Guiding Post-Surgical Decisions: After a radical prostatectomy, genomic tests help determine if a patient needs immediate backup treatments like adjuvant radiation or hormone therapy. If your post-surgery genomic profile shows a low risk of recurrence despite a high Gleason score, you may be able to safely avoid additional therapies and their side effects.

Clarifying Ambiguous Profiles: In cases where clinical markers conflict—such as an intermediate Gleason score paired with an unexpectedly high PSA level—a genomic test serves as a tie-breaker. It looks at the actual genetic behavior of the cells to clarify whether the tumor is behaving safely or aggressively, establishing the clearest path forward.

The Value of an Expert Pathology Second Opinion

Seeking a second opinion for a high-risk prostate cancer diagnosis (Gleason scores 8, 9, or 10) is a crucial step to ensure diagnostic accuracy before finalizing a treatment plan. While your initial diagnosis confirms the presence of cancer, a second pathology review focuses entirely on verifying the exact cellular grades.

Interpreting prostate biopsy tissue slides under a microscope involves an element of subjectivity. Different pathologists may assign slightly different structural grades to the same tissue sample.

For a high-stakes diagnosis where the exact grade completely changes your treatment path—such as distinguishing between a dominant intermediate-grade $4+3=7$ (Grade Group 3) and a high-risk $3+5=8$ (Grade Group 4)—having a dedicated expert urological pathologist review your slides provides vital confirmation. This second look can lead to a significant re-classification that protects you from under-treatment or unnecessary over-treatment, ensuring your care plan is built on an incredibly accurate foundation.

Conclusion

A high Gleason score suggests that prostate cancer cells are more likely to grow quickly or spread beyond the prostate, but it does not determine the outcome by itself. Many people with higher Gleason scores benefit from effective treatments such as surgery, radiation therapy, hormone therapy, chemotherapy, or newer targeted approaches, depending on the stage of the disease.

Your healthcare provider will evaluate the Gleason score together with PSA levels, imaging findings, and the extent of the cancer to develop an individualized treatment plan. Understanding what the Gleason score represents can help you make informed decisions and have more meaningful discussions with your cancer care team.

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Frequently Asked Questions

1. What is a Gleason score?

A Gleason score is a grading system used to describe how abnormal prostate cancer cells appear under a microscope. It is calculated by adding the grades of the two most common patterns of cancer cells found in a biopsy, resulting in a score between 6 and 10. Lower scores generally indicate slower-growing cancers, while higher scores suggest a greater likelihood of aggressive behavior. The Gleason score is often reported together with the Grade Group classification.

2. What is considered a high Gleason score?

A Gleason score of 8, 9, or 10 is generally considered high-grade prostate cancer. These cancers tend to grow and spread more quickly than tumors with Gleason scores of 6 or 7. However, a high score does not necessarily mean the cancer has already spread. Additional tests, including imaging and PSA measurements, help determine the stage and extent of the disease.

3. Does a high Gleason score mean the cancer is advanced?

Not always. A high Gleason score describes how aggressive the cancer cells appear, but it does not indicate how far the cancer has spread. Some people have high-grade cancer that is still confined to the prostate and may be treated with curative intent. Doctors use the Gleason score together with tumor stage, PSA level, and imaging results to determine the overall stage of prostate cancer.

4. How does a Gleason score affect treatment?

The Gleason score plays a major role in choosing the most appropriate treatment plan. Higher scores are more likely to require active treatment, such as surgery, radiation therapy, hormone therapy, or a combination of therapies. Lower-risk cancers may be managed with active surveillance in selected patients. Your age, overall health, and personal preferences are also considered when making treatment decisions.

5. Can a high Gleason score be treated successfully?

Yes. Many people with a high Gleason score respond well to modern prostate cancer treatments, particularly when the disease is diagnosed before it has spread extensively. Advances in surgery, radiation therapy, hormone therapy, chemotherapy, and targeted therapies have improved outcomes for many patients. Regular follow-up is important to monitor treatment response and detect any recurrence as early as possible.

6. What is the difference between a Gleason score and a Grade Group?

The Gleason score and Grade Group both describe the aggressiveness of prostate cancer, but the Grade Group system is a newer, simpler way to classify risk. Grade Groups range from 1 to 5, with higher numbers indicating more aggressive cancer. Doctors often report both systems together because they provide complementary information that helps guide treatment and discuss prognosis with patients.

Sources

American Cancer Society. Understanding Your Pathology Report: Prostate Cancer (Gleason Score and Grade Group).
National Cancer Institute. Prostate Cancer Treatment (PDQ®). 
Mayo Clinic. Prostate Cancer.
Cleveland Clinic. Gleason Score. 
Prostate Cancer Foundation. Understanding Prostate Cancer Grading and Staging. 
National Comprehensive Cancer Network. NCCN Guidelines for Patients: Prostate Cancer. 
American Urological Association. Localized Prostate Cancer Guidelines.