What does an MRI prostate grade 2 or 59% finding imply and what are the next steps for diagnosis and treatment?

Understanding MRI Prostate Grade 2 or 59%

What This Finding Means

An MRI prostate finding described as "grade 2" or "59%" most likely refers to a PI-RADS score of 2, which indicates a very low probability (approximately 12%) of clinically significant prostate cancer. 1

The terminology requires clarification:

• PI-RADS 2 lesions carry approximately 12% risk of clinically significant cancer (defined as Gleason score ≥3+4 or ISUP grade group ≥2) 1
• If "59%" refers to a percentage involvement metric, this would need correlation with the actual PI-RADS score and biopsy findings to determine significance 1

Risk Stratification Based on PI-RADS Score

The predictive value for clinically significant cancer increases stepwise with PI-RADS/Likert scores 1:

• PI-RADS 1-2: 3-12% risk of clinically significant cancer
• PI-RADS 3: 21% risk
• PI-RADS 4: 58% risk
• PI-RADS 5: 81% risk

Next Steps for Diagnosis

For a PI-RADS 2 lesion, the decision to proceed with biopsy should be guided by PSA density (PSA-D) and clinical risk factors, not by MRI findings alone. 1, 2

Biopsy Decision Algorithm

1. Calculate PSA density (serum PSA ÷ prostate volume in cc) 1

   • PSA-D <0.10 ng/ml/cc with PI-RADS 2: Very low risk, biopsy may be deferred 1
   • PSA-D 0.10-0.15 ng/ml/cc with PI-RADS 2: Low-intermediate risk, consider clinical factors 1
   • PSA-D >0.15 ng/ml/cc with PI-RADS 2: Proceed with systematic biopsy 1

2. If biopsy is indicated, perform standard 12-core systematic TRUS-guided biopsy 1, 2

   • Do not rely on MRI-targeted biopsy alone for PI-RADS 2 lesions 2
   • Systematic biopsy remains the standard of care even with negative or low-grade MRI findings 2

3. Additional risk factors that lower the threshold for biopsy 1, 2:

   • Abnormal digital rectal examination
   • Family history of prostate cancer
   • African ancestry
   • Age >60 years
   • Rising PSA velocity

Critical Pitfalls to Avoid

A negative or low-grade MRI (PI-RADS 1-2) does NOT exclude clinically significant prostate cancer. 2

• Approximately 12% of men with PI-RADS 2 lesions harbor clinically significant cancer 1
• MRI has high sensitivity (88-93%) but variable specificity (37-41%) for significant cancer 1
• The "rule out" performance of MRI is better than its "rule in" performance, meaning negative scans are more reliable than positive scans 1
• Never forego biopsy based solely on MRI findings when clinical suspicion remains high (elevated PSA-D, abnormal DRE, strong risk factors) 2

If Biopsy is Performed

Each biopsy core should be reported with 1:

• Location
• Gleason score and ISUP grade group
• Percentage of core involvement
• Presence of cribriform or intraductal carcinoma (high-risk features) 1

Note: ISUP grade group 2 cancers (Gleason 3+4) detected by MRI-targeted biopsy have better prognosis than those detected by systematic biopsy alone, representing a grade shift phenomenon 1

Management Based on Biopsy Results

If biopsy confirms ISUP grade group 2 (Gleason 3+4) with favorable features 1:

• <10% Gleason pattern 4
• PSA <10 ng/ml
• ≤3 positive cores
• <50% involvement per core
• No cribriform or intraductal histology

Active surveillance may be offered with close monitoring including repeat biopsies at least every 3 years 1

If biopsy shows ISUP grade group 3 or higher, or unfavorable grade group 2 features, exclude from active surveillance and proceed with definitive treatment (radical prostatectomy or radiotherapy with ADT) 1