Does size matter? Tumor density as a predictor of clinically significant prostate cancer on MRI-targeted transperineal prostate biopsy.

Purpose

Prior studies of tumor burden as a predictor of clinically significant prostate cancer (csPCa) consist of per-patient analyses or are limited by imprecise size measurements. This study evaluates tumor density (TD) as a lesion-level predictor of csPCa on magnetic resonance imaging (MRI)-targeted biopsy.

Methods

We reviewed patients who consecutively underwent MRI-ultrasound fusion transperineal biopsy for suspicion of csPCa from July 2023 to August 2025 at a tertiary academic center. TD was calculated using exact lesion volume generated by fusion software divided by MRI prostate volume. The primary outcome was per-lesion detection of csPCa, defined as International Society of Urological Pathology Grade Group (GG) ≥2. We assessed the association between TD and csPCa using generalized estimating equation logistic regression models and provided estimates of discrimination and clinical benefit.

Results

The cohort included 349 patients with 496 PI-RADS 3-5 lesions, of which 34.7% harbored csPCa. Lesions with csPCa had greater median TD than those without (0.013 vs. 0.006, p<0.001). On univariate analysis, greater TD was associated with higher odds of csPCa (OR 1.59, 95% CI 1.39-1.83, p<0.001). In multivariable analysis adjusting for age, race, family history, PSA, PI-RADS score, lesion location, and biopsy history, TD remained independently associated with csPCa (OR 1.44, 95% CI 1.20-1.71, p<0.001). Adding TD to the baseline multivariable model also led to improvement in AUC (ΔAUC 0.024, 95% CI 0.017-0.029; p=0.004).

Conclusion

TD was independently associated with csPCa on targeted biopsy and showed moderate discrimination. TD is a readily available metric which may improve lesion-level risk stratification beyond standard clinical and imaging information.