Understanding PI-RR
PI-RR stands for Prostate Imaging for Recurrence Reporting. It is a structured MRI scoring system for estimating the likelihood of local prostate cancer recurrence after whole-gland treatment, specifically radiation therapy or radical prostatectomy.
The practical goal is simple: when PSA is rising after treatment, PI-RR helps the radiologist describe whether there is a suspicious local target for biopsy, salvage therapy, or focused clinical follow-up.
How the score works
PI-RR uses a familiar 1–5 likelihood scale:
| PI-RR score | Practical meaning |
|---|---|
| PI-RR 1 | Very low likelihood of local recurrence |
| PI-RR 2 | Low likelihood of local recurrence |
| PI-RR 3 | Equivocal or uncertain for local recurrence |
| PI-RR 4 | High likelihood of local recurrence |
| PI-RR 5 | Very high likelihood of local recurrence |
Why DCE becomes so important
PI-RR is different from PI-RADS because the prostate has already been treated. After radiation therapy, the gland may be fibrotic and heterogeneous. After prostatectomy, the radiologist is evaluating the prostatectomy bed rather than an intact gland. In both settings, recurrent tumor often stands out as focal early enhancement on dynamic contrast-enhanced MRI.
DWI/ADC remains important because recurrent tumor may restrict diffusion, but susceptibility artifact from brachytherapy seeds, fiducial markers, or surgical clips can limit diffusion images. T2-weighted imaging remains useful for anatomy and morphology, but DCE is often the key sequence that makes a recurrence visible.
Radiation therapy vs radical prostatectomy
After radiation therapy, PI-RR evaluates the treated gland. DWI and DCE both contribute to the overall score, and concordant focal diffusion restriction plus early enhancement increases confidence for recurrence.
After radical prostatectomy, PI-RR evaluates the prostatectomy bed, especially the vesicourethral anastomosis and expected surgical margins. DCE is the dominant sequence, while DWI can support or upgrade suspicion when the images are reliable.
What PI-RR is not
PI-RR is not a replacement for PI-RADS in the untreated prostate and it is not designed for focal therapy follow-up. A new lesion in untreated prostate tissue should generally be assessed with PI-RADS v2.1. A suspicious finding at the ablation zone or ablation margin after focal therapy should be assessed with PI-FAB logic.
Related tools and articles
References and further reading
- Panebianco V, Villeirs G, Weinreb JC, et al. Prostate Magnetic Resonance Imaging for Local Recurrence Reporting (PI-RR): International Consensus-based Guidelines on Multiparametric Magnetic Resonance Imaging for Prostate Cancer Recurrence after Radiation Therapy and Radical Prostatectomy. Eur Urol Oncol. 2021.
- Shetty AS, et al. Prostate Imaging for Recurrence Reporting: User Guide. RadioGraphics. 2025.
- Abreu-Gomez J, et al. PI-RR: The Prostate Imaging for Recurrence Reporting System for MRI of Local Prostate Cancer Recurrence After Radiation Therapy and Radical Prostatectomy. AJR Am J Roentgenol. 2023.