The Gleason score explained — what your grade means for treatment

Your biopsy report has come back with a Gleason score. Perhaps it says "Gleason 3+4=7" or "Grade Group 2." These numbers are among the most important pieces of information in prostate cancer diagnosis — they describe how aggressive the cancer is and guide every subsequent treatment decision.

Understanding your Gleason score does not require a medical degree. This article explains exactly what it means in plain language.

1. What the Gleason score measures

The Gleason score is a pathological grading system developed by Dr. Donald Gleason in the 1960s. It describes how abnormal the cancer cells look under the microscope compared to normal prostate tissue — and this abnormality predicts how aggressively the cancer is likely to behave.

Normal prostate cells have a regular, organised arrangement of glands. As cancer develops, these cells lose their normal architecture — they become less organised, more irregular, and progressively more difficult to recognise as prostate cells. The Gleason system grades this disruption from Pattern 1 (near-normal) to Pattern 5 (completely disorganised, no glandular structure).

2. How the score is calculated

The Gleason score is the sum of two pattern numbers:

• Primary pattern: The most prevalent (most common) pattern seen in the biopsy cores
• Secondary pattern: The second most common pattern seen

These two numbers are added to give the total score. For example, if the most common pattern is 3 and the second most common is 4, the Gleason score is 3+4=7. The order matters — a 3+4 tumour is less aggressive than a 4+3 tumour, even though both add up to 7.

3. Grade Groups — the modern classification

Because the Gleason scoring system was confusing (Gleason 6 sounds like the middle of a 2–10 scale, but it is actually the lowest possible biopsy score), the International Society of Urological Pathology (ISUP) introduced a Grade Group system in 2014. Most reports now include both.

4. What your grade means for treatment

Grade Group 1 (Gleason 6)

This is the lowest-risk prostate cancer detectable on biopsy. Many urologists now debate whether Gleason 6 should even be called "cancer" — it has essentially no metastatic potential and the vast majority of men with this grade will die of something else entirely. Active surveillance — monitoring with regular PSA, MRI, and repeat biopsies rather than immediate treatment — is now the standard of care for most Grade Group 1 patients.

Grade Group 2–3 (Gleason 7)

Intermediate-risk disease. Treatment is generally recommended for GG3 and often for GG2 in younger patients. The choice between robotic surgery and radiation is based on tumour volume, patient age, bladder/sexual function concerns, and patient preference.

Grade Group 4–5 (Gleason 8–10)

High-risk disease requiring prompt treatment. Surgery (RARP with extended lymph node dissection) or radiation with hormone therapy are the standard options. Staging investigations — CT, bone scan, or PSMA PET — are essential to confirm disease has not spread before local treatment.

5. Other factors alongside Gleason grade

The Gleason grade is the most important single factor — but it is not the only one. Risk stratification for prostate cancer uses several variables together:

• PSA level: PSA below 10 = low risk; 10–20 = intermediate; above 20 = high risk (in combination with other factors)
• Clinical stage: T1–T2 (organ-confined) vs T3 (extraprostatic extension) vs T4 (invasion of adjacent structures)
• Number of biopsy cores positive: 1 of 12 vs 8 of 12 implies very different tumour burden
• Percentage of cores involved: High percentage involvement suggests larger tumour volume
• Perineural invasion: Cancer along nerve fibres — suggests extraprostatic spread is more likely