Predictors of Histological Upgrading at Radical Prostatectomy in Patients With Localised Low-Grade Prostate Cancer and Pretreatment Biparametric MRI

Background: PSA density has previously been identified as a predictor of histological upgrading at radical prostatectomy in men eligible for active surveillance, but how information from pretreatment biparametric magnetic resonance imaging (bpMRI) contributes needs further clarification. The objective of this register-based study was to identify predictors of upgrading at prostatectomy in men with Gleason Grade (GG) group 1 and pretreatment bpMRI. Methods This study included all 130 men with GG 1 cancer who between March 2014 and September 2019 had a robotic-assisted radical prostatectomy (RARP) at Innlandet Hospital Trust and a bpMRI before their diagnostic biopsy. The outcome measure was upgrading from GG 1 on biopsy to GG 2–5 in the radical prostatectomy specimen. Logistic regression models were used to explore predictors for upgrading. Odds ratios (ORs) and confidence intervals (CIs) were calculated. The association between PSA density and the probability of upgrading was assessed after stratifying by Prostate Imaging-Reporting and Data System and Reporting Datasystem (PI-RADS): PI-RADS 1–3 versus 4–5. Results Upgrading was present in 56% (73/130) of the cancers. PSA density was the only significant predictor for upgrading (OR = 1.7, 95% CI 1.2; 2.5). The probability of upgrading was higher for men with a PIRADS 1–3 than for men with PIRADS 4–5, but the difference was not statistically significant (adjusted OR 0.4, 95% CI 0.2; 1.1, p = 0.082). However, among men with PI-RADS 1–3, the probability gradually increased with increasing PSA density (p = 0.036). With PI-RADS 4–5 the probability of upgrading was high over the entire PSA density range. Conclusion PSA density is a clinically important factor to predict upgrading from GG 1 to GG 2–5 when bpMRI shows no suspicious lesion. In men with a suspicious tumour on bpMRI (PI-RADS 4–5), the probability of an undetected GG 2–5 cancer is high regardless of the PSA density.