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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/m2] 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.

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Objective: Benign prostatic hyperplasia (BPH) and prostate cancer (PCa) are the two most common urologic diseases in aging males. The negative association between prostate/BPH size and incidence of PCa is well documented in the literature. However, the exact mechanism is not well understood. This study aims to further investigate the possible effect of prostate volume on prostate capsule thickness and glandular cell density in the prostatic peripheral zone (PZ). Materials and Methods: A total of 100 patients were selected that had undergone radical prostatectomy with prostate sizes ranging from 20 to 160 mL. Quantitative measurements of capsule thickness and density of epithelial glands within the peripheral zone not affected by cancer were analysed and calculated on histo-anatomical slides using computer-based imaging software. Associations between the different variables were calculated using Spearman correlation with 95% confidence intervals (CIs). Results: In the non-cancerous areas of the PZ, prostate volume and average capsule thickness are positively associated ( rs = +0.6526, 95% CI +0.5233 to +0.7526, p < 0.0001), while prostate volume and average glandular epithelial cell density of the PZ are negatively associated ( rs = −0.6011, 95% CI −0.7133 to −0.4589, p < 0.0001). These associations remain consistent on subgroup analysis. Conclusion: The findings of this study support the hypothesis that transition zone (TZ) growth in large BPH prostates may cause pressure on the outer PZ, leading to fibrosis and atrophy of the glandular tissue. This may provide a protective effect against PCa, as most PCa originates in the PZ of the prostate. Level of evidence: Not applicable