PI-RR：放射線療法または根治的前立腺摘除術後の局所前立腺癌再発評価のための報告システム

Biochemical recurrence, marked by rising prostate specific antigen levels, is a common and challenging clinical scenario following curative treatments for localized prostate cancer (PCa), such as radical prostatectomy (RP) or radiation therapy (RT). An accurate assessment is critical for detecting local recurrence and distinguishing it from distant metastatic disease, thereby guiding salvage therapies. While multiparametric MRI has demonstrated strong performance in detecting local recurrence, the lack of standardized reporting has historically limited its clinical utility and reproducibility. To address this variability, an international consensus-based Prostate Imaging for Recurrence Reporting (PI-RR) system was introduced in 2021. PI-RR adopts a 5-point Likert scale, similar to Prostate Imaging Reporting and Data System, but places greater emphasis on dynamic contrast-enhanced MRI and incorporates knowledge of the prior primary tumor location to grade the likelihood of recurrence. This review article provides a comprehensive overview of the PI-RR system, detailing its imaging acquisition recommendations, specific scoring criteria after RT and RP, clinical implications, and future directions within the evolving landscape of PCa imaging.