Your MRI Results Indicate a High Likelihood of Clinically Significant Prostate Cancer and You Should Proceed with Prostate Biopsy
Given your two PI-RADS 4 lesions in the peripheral zone, you have approximately a 70% probability of harboring clinically significant prostate cancer (Gleason score ≥3+4), and biopsy is strongly recommended regardless of your PSA density. 1
Understanding Your PI-RADS Scores
Your MRI identified three lesions with different risk levels:
PI-RADS 4 lesions (Lesions #1 and #2): These carry the highest concern. Large validation studies demonstrate that PI-RADS 4-5 lesions are associated with clinically significant cancer in 67-71% of cases. 1 The probability of cancer detection for PI-RADS 4 specifically is approximately 71%. 1
PI-RADS 3 lesion (Lesion #3): This represents an equivocal finding with approximately 17-31% probability of clinically significant cancer. 1, 2
Why Biopsy is Necessary in Your Case
Patients with PI-RADS ≥4 lesions should undergo prostate biopsy regardless of PSA density. 3 Your PSA density of 0.07 ng/mL² is actually quite low, but this does not change the recommendation when PI-RADS 4 lesions are present. 3
The evidence is clear on this point:
- For PI-RADS ≥4 lesions, the clinically significant cancer risk remains ≥40% regardless of PSA density values. 3
- PI-RADS v2 demonstrates high diagnostic accuracy with 89% sensitivity and 73% specificity for prostate cancer detection. 1, 4
- The system is specifically designed to identify cancers that matter clinically while avoiding overdiagnosis of indolent disease. 1, 4
What About Your PI-RADS 3 Lesion?
Your larger transition zone lesion (22 mm, PI-RADS 3) presents a different consideration:
- With your PSA density of 0.07 ng/mL², which is well below the 0.10 ng/ml/cm³ threshold, this lesion alone would not mandate biopsy. 3
- Using a PSAD cutoff of 0.10 for PI-RADS 3 lesions would save approximately 32% of biopsies while missing only 7% of clinically significant cancers. 3
- However, since you're proceeding with biopsy due to your PI-RADS 4 lesions, this area should also be sampled. 5
Recommended Biopsy Approach
You should undergo MRI-directed targeted biopsy of all three lesions plus systematic biopsy. 4 This combined approach is critical because:
- Targeted biopsy alone can miss clinically significant cancer, particularly in PI-RADS 3 lesions. 5
- In one study of PI-RADS 3 lesions, systematic biopsies detected clinically significant cancer that would have been missed by targeted biopsy alone in multiple patients. 5
- The European Association of Urology guidelines recommend MRI-directed biopsy plus systematic biopsy for PI-RADS 4-5 lesions in biopsy-naïve patients. 4
Important Caveats
Common pitfall to avoid: Do not be falsely reassured by your low PSA density. While PSA density is valuable for risk stratification in PI-RADS 3 lesions, it does not reduce the cancer probability sufficiently in PI-RADS 4 lesions to avoid biopsy. 3
What the biopsy may show:
- Your peripheral zone lesions (PI-RADS 4) have the highest concern for Gleason ≥3+4 disease. 1
- Index lesions with Gleason ≥3+4 pattern and volume ≥0.2 ml (approximately 7-8 mm diameter) are typically identifiable on modern MRI, and both your PI-RADS 4 lesions exceed this size threshold. 1
- No extraprostatic extension was noted on your MRI, which is favorable if cancer is present. 1
Quality consideration: Your MRI was performed at a high-quality academic center (University of Wisconsin-Madison), which enhances the reliability of these PI-RADS scores. 4