Clinical Scorecard: Evaluating Diffusion Metrics for the Quantitative Analysis of Apparent Diffusion Coefficient in Prostate MRI: A Bicentric Proof-of-Concept Investigation

At a Glance

Key Highlights

• DWI is essential in prostate MRI, especially for peripheral zone lesions, influencing biopsy decisions via PI-RADS categorization.
• ADC values have potential as biomarkers but lack standardized quantification due to variability across readers, equipment, and protocols.
• Diffusion levels (DLs) derived from ADC ranges, as used in breast MRI, may standardize prostate lesion assessment and complement PI-RADS.

Guideline-Based Recommendations

Diagnosis

• Use DWI and ADC maps as key components in prostate MRI interpretation, focusing on peripheral zone lesions.
• Apply PI-RADS version 2.1 criteria for lesion categorization, considering ADC values between 0.75–0.90 × 10⁻³ mm²/s to differentiate benign from malignant tissue.
• Consider developing and validating diffusion levels (DLs) from ADC data to improve risk stratification and biopsy targeting.

Management

• Perform systematic 12-core prostate biopsy plus targeted biopsy of PI-RADS ≥ 3 lesions.
• Exclude patients on 5-alpha reductase inhibitors to avoid reduced lesion conspicuity on high b-value DWI.
• Use fusion ultrasound-mpMRI guidance for targeted biopsy with experienced urologists performing the procedure.

Monitoring & Follow-up

• Monitor PSA levels and digital rectal examination findings to guide MRI and biopsy decisions.
• Use histopathological ISUP grading (≥2) as the standard for clinically significant prostate cancer.
• Consider repeat MRI and biopsy based on clinical risk factors and imaging findings.

Risks

• Variability in ADC measurements may affect diagnostic accuracy and reproducibility.
• Non-standardized biopsy indications in MRI-negative patients may lead to inconsistent detection of significant cancer.
• Use of reference tissues for ADC ratio calculation may yield irreproducible results due to tissue heterogeneity.

Patient & Prescribing Data

Men undergoing prostate MRI and biopsy for suspected prostate cancer, predominantly Caucasian ethnicity, aged ≥18 years.

MRI findings, particularly PI-RADS category and ADC-derived diffusion levels, guide biopsy decisions; exclusion of 5-alpha reductase inhibitors improves imaging quality.

Clinical Best Practices

• Standardize ADC measurement protocols across centers to reduce variability.
• Implement diffusion level (DL) classification to complement PI-RADS and refine biopsy targeting.
• Use dual DWI sequences with b-values ≥1000 s/mm² for ADC map generation.
• Ensure biopsy includes both systematic and targeted cores for comprehensive assessment.
• Maintain blinding of image readers to biopsy results to reduce bias in ADC evaluation.

References

• PI-RADS v2 and v2.1 guidelines
• European Society of Breast Imaging DWI working group consensus
• Bickel et al. ADC diffusion levels in breast MRI
• ISUP grading for prostate cancer