# Prostate Cancer Index Density, the Ratio of Percentage of Biopsy-Positive Cores to Prostate Volume, and Predicted Lethal Disease in the EAU Intermediate Prognostic Risk Class: Analysis and Implications in 651 Consecutive Patients Treated with Robot-Assisted Radical Prostatectomy at a Tertiary Referral Centre

## TL;DR

A new prostate cancer risk metric combining biopsy results and prostate size better predicts aggressive tumors than existing methods.

## Contribution

The study introduces and validates a novel index (Id-BPC) that improves prediction of lethal prostate cancer in intermediate-risk patients.

## Key findings

- Id-BPC showed stronger associations with tumor grades than biopsy-positive cores alone.
- Higher Id-BPC values correlated with increased likelihood of lethal (ISUP 4/5) tumors.
- The index remained significant even after adjusting for clinical factors.

## Abstract

This study evaluates the relationship between the percentage of positive prostate biopsy samples (PBS) and prostate volume, defined as the density index (Di-PBS), as a predictor of high tumour grade in surgical specimens from European Association of Urology (EAU) intermediate-risk patients undergoing robotic surgery. Between 2013 and 2021, 651 patients with no previous treatment were analysed, with tumour grades classified as indolent (ISUP 1), significant (ISUP 2/3), and lethal (ISUP 4/5). Of the patients, 82.2% had ISUP 2/3 tumours, 15.2% had ISUP 4/5 tumours, and 4.6% had ISUP 1 tumours, with Id-BPC showing a stronger association than BPC alone in predicting lethal and significant tumours (even after adjustment for clinical factors), associating higher Id-BPC values with a higher probability of ISUP 4/5 tumours, suggesting its potential role in risk stratification.

Background/Objectives: The ratio of percentage of prostate cancer (PCa) biopsy-positive cores (BPC) to prostate volume as the index density factor (Id-BPC) was used to predict the risk of high tumour grades in the surgical specimens of European Association of Urology (EAU) intermediate-risk patients treated with robotic surgery. Methods: From January 2013 to December 2021, we evaluated 651 patients without any prior treatment for PCa. In the surgical specimen, tumour grades were classified as indolent (International Society of Urological Pathologists Classification (ISUP) 1), significant (ISUP 2/3), and lethal (ISUP 4/5). Associations with the risk of significant and lethal cancers were assessed by the multinomial logistic regression model. Results: Tumour grade was clinically significant (ISUP 2/3) in 522 (80.2%) cases and lethal (ISUP 4/5) in 99 (15.2%), while the results were not significant (ISUP 1) in 30 (4.6%) subjects. The association of Id-BPC was always stronger than BPC for ISUP 1 vs. 4/5 (OR = 0.284; 95% CI: 0.128–0.632; p = 0.002), ISUP 2/3 vs. 4/5 (OR = 0.744; 95% CI: 0.586–0.946; p = 0.016), and ISUP 1 vs. 2/3 (OR = 0.382; 95% CI: 0.176–0.828; p = 0.015), and this trend held after adjusting for clinical factors. Conclusions: Accordingly, Id-BPC was positively associated with lethal disease, as, when it increased or decreased, it was more or less likely, respectively, to find ISUP 4/5 in the surgical specimens of the operated subjects, who could have been stratified according to Id-BPC risk levels.