Quantitative measurements of prostatic zones by MRI and their dependence on prostate size: possible clinical implications in prostate cancer

Aim: Many studies support an inverse relationship between benign prostate hypertrophy (BPH) size and incidence of prostate cancer (PCa), but the causal link between these conditions is poorly understood. Recent studies suggest that a growing transition zone (TZ) in the prostate may induce pressure on the outer peripheral zone (PZ), leading to atrophy of the glandular tissue where PCa often originates, providing a possible explanation for this interaction. To further investigate this phenomenon, our pilot study uses magnetic resonance imaging (MRI) to examine quantitative zonal changes in a consecutive cohort of prostates. Methods: MRI scans of male patients [ n = 204, 61.57 ± 13.90 years, average body mass index (BMI) 29.05 kg/m 2 ] with various prostate sizes were analyzed statistically to identify possible associations between prostate parameters, such as total prostate volume (TPV) and peripheral zone thickness (PZT). Results: TPV and PZT demonstrated a weak, inverse correlation ( r = −0.21, p = 0.002). However, when examining the plotted data, the relationship between TPV and PZT was significantly different when the cohort was divided into two groups; lower TPV: ⩽87.5 ml ( n = 188, TPV xˉ = 36.01 ± 18.18 ml), and higher TPV: >87.5 ml ( n = 17, TPV xˉ = 125.69 ± 41.13 ml). Average PZT differed significantly between these groups (z = −3.5554, p = 0.0004). Conclusions: PZT was significantly different for patients with lower versus higher TPVs, suggesting that, above a certain point of BPH growth, the PZ is unable to withstand pressure from an expanding TZ, supporting the notion that growing BPH causes compression of the PZ glandular tissue, and, therefore, BPH may be protective against PCa.