Does Size Matter? A Retrospective Study Analysing the Size of PI-RADS 4 Lesions and Its Associated Prostate Cancer Positivity with Transperineal Prostate Biopsy.

Introduction: Magnetic resonance imaging (MRI) is an essential tool in Prostate Cancer (PCa) diagnosis. PI-RADS v2.1 score correlates with clinically significant prostate cancer (CSPCa) and according to the most recent guidelines, prevalence of CSPCa with PI-RADS 4 is 33-41%, while PI-RADS 5 is 62-79%. These groups are separated only by a size of 15 mm yet the difference in risk is significant. This study aims to find a size threshold associated with CSPCa within the PI-RADS 4 group, which may be used in combination with other prostatic parameters, such as PSA density in order to help with risk stratification and patient counselling in the pre-biopsy setting. This may also aid with surveillance of smaller PI-RADS 4 lesions in the setting of a negative biopsy and avoid unnecessary repeat biopsies unless triggered by a size threshold.

Methods: A retrospective study was performed with data from 407 patients undergoing transperineal prostate biopsy (TPPB) between April 2022 and November 2023. A subgroup of patients with PI-RADS 4 was included for analysis. A ROC-AUC was obtained.

Results: Median age was 67 (interquartile range: 61-71) and PSA density 0.20 (interquartile range 0.13-0.28). PI-RADS score correlated with CSPCa: for PI-RADS 1 and 2, the frequency of CSPCa was 10%; for PI-RADS 3, it was 20%; for PI-RADS 4, it was 60%; and for PI-RADS 5, it was 80%, Pearson correlation = 0.51, p < 0.001. The Receiver Operating Characteristic Area Under the Curve (ROC-AUC) was determined to be 0.664 [0.579-0.7499]. The optimal cut-off point was 8.5 mm. Patients with lesions larger than 8.5 mm had 2.31 times higher risk CSPCa.

Conclusion: PI-RADS 4 size does matter and is a useful predictor of CSPCa. In our study, a cut-off of 8.5 mm was identified. The combination of PI-RADS 4 with PSA density provides a specificity higher than 80% for CSPCa detection.