The Significance of Gleason Score in Determining Prostate Cancer Treatment
The Gleason score is a critical determinant in risk stratification for prostate cancer that directly guides treatment decisions based on tumor aggressiveness, with higher scores (8-10) indicating more aggressive disease requiring more intensive treatment approaches. 1
Understanding the Gleason Scoring System
The Gleason score represents the sum of the two most predominant histological patterns observed in prostate cancer tissue, with each pattern graded from 1 to 5 based on the degree of architectural differentiation:
- Scoring method: Each pattern is scored 1-5, with 5 being most poorly differentiated
- Total score calculation: Sum of the two most common patterns (range: 2-10)
- Example: If grade 3 is most common and grade 4 is second most common, the Gleason score is 7 (3+4)
Interpretation of Scores:
- Grade 6: Well-differentiated histology (lower risk)
- Grade 7: Intermediate differentiation
- 3+4 is less aggressive than 4+3
- Grades 8-10: Poorly differentiated with worst prognosis (high risk) 1
Risk Stratification Based on Gleason Score
Gleason score is a primary component in risk classification systems that guide treatment decisions:
Risk Categories:
Low Risk:
- Gleason score ≤6
- PSA <10 ng/mL
- Clinical stage T1-T2a 1
Intermediate Risk:
- Gleason score 7
- PSA 10-20 ng/mL
- Clinical stage T2b 1
High Risk:
- Gleason score 8-10
- PSA >20 ng/mL
- Clinical stage T2c or higher 1
Treatment Algorithms Based on Gleason Score and Risk Category
Low Risk (Gleason ≤6):
- CALE <10 years: Observation only
- CALE ≥10 years: Observation, radical prostatectomy, external beam radiation therapy, or brachytherapy 1
Intermediate Risk (Gleason 7):
- CALE <10 years: Observation or radical prostatectomy or EBRT (with or without brachytherapy; with or without hormone therapy for 4-6 months)
- CALE ≥10 years: Radical prostatectomy or EBRT (with or without brachytherapy; with or without hormone therapy for 4-6 months) 1
High Risk (Gleason 8-10):
- CALE <5 years: Observation only
- CALE ≥5 years: Radical prostatectomy or EBRT (with or without brachytherapy; with or without hormone therapy for 2-3 years) 1
Note: CALE = Comorbidity-adjusted life expectancy
Prognostic Implications of Gleason Score
The Gleason score has significant prognostic value:
Biochemical control rates at 5 years:
- Gleason 2-4: 78%
- Gleason 5-6: 63%
- Gleason 7: 37%
- Gleason 8-10: 33% 2
Probability of prostate cancer death:
- Gleason score ≥7: 29% probability
- Gleason score ≥8: 48% probability 3
Important Clinical Considerations
Tertiary patterns: Tumors with tertiary Gleason grade 4 or 5 behave more aggressively than their primary score would suggest 1
Reporting standards: The maximum length of cancer involvement in each core and both the commonest and worst Gleason grades should be reported in biopsies 1
Interobserver variability: There can be significant discordance in Gleason grading between pathologists, particularly between genitourinary-trained and non-genitourinary pathologists 4
Gleason 7 significance: Patients with Gleason 7 should not be grouped with those having Gleason 5-6, as they have significantly worse outcomes and may benefit from more aggressive treatment 2
Pitfalls to Avoid
Underestimating Gleason 7: A common mistake is grouping Gleason 7 with lower-grade tumors, when it actually requires more aggressive management 2
Ignoring pattern order: A 4+3=7 score carries worse prognosis than 3+4=7 1
Patient misunderstanding: Despite its importance, patient knowledge of the Gleason scoring system is often poor, which can impact shared decision-making 5
Post-treatment grading: Tumor grade should not be assessed in patients who have received radiotherapy or hormonal therapy 1
The Gleason score remains one of the most powerful predictors of prostate cancer behavior and should be carefully considered alongside PSA levels, clinical stage, and patient factors when determining the optimal treatment approach.