4K density: Adjusting the 4Kscore for prostate volume to improve risk stratification of clinically significant...

The 4K Score is a blood-based test that estimates the risk of clinically significant prostate cancer (Grade Group ≥2, GG2 + ) by combining four kallikrein markers with clinical variables. However, benign prostatic hyperplasia (BPH) can elevate PSA levels, potentially leading to risk overestimation in men with large prostates. We developed a novel metric, 4K Density (4K Score divided by prostate volume), to adjust for prostate size and improve risk stratification.

We retrospectively reviewed 3150 men who underwent 4K Score testing at the University of Miami Desai Sethi Urology Institute from 2014 to 2024. After excluding those without a prostate biopsy or MRI within six months of the 4K Score, 1983 men remained. Statistical analysis using SAS v9.4 included logistic regression, receiver operating characteristic (ROC) analysis, and Youden's Index to determine optimal cutoffs for GG2+ detection. The performance of 4K Density was compared to the 4Kscore and PSA Density in predicting GG2+ cancer.

Among the 1983 men, 661 (33%) had GG2+ cancer. 4K Density was significantly higher in men with GG2+ cancer compared to those without (median 0.93 vs. 0.25, p < .0001). In multivariable analysis, 4K Density was the strongest independent predictor (OR 3.51, 95% CI 3.64-4.66), outperforming 4Kscore and PSA density. 4K Density also had the highest AUC (0.81, (95%CI)), compared to 4Kscore (0.76, 95 %CI, <0.0001) and PSA density (0.76, 95% CI, <0.0001). At an optimized cutoff of 0.56, 4K Density achieved 89.9% NPV and 48.5% PPV for detecting GG2+ cancer.

4K Density is a novel, volume-adjusted biomarker that improves detection of clinically significant prostate cancer and outperforms PSA density and the 4Kscore test. It may be helpful in larger prostates, where confounding from BPH is present. Prospective validation is warranted to confirm its clinical utility.