Published in
UROLOGICONCOLOGY
2022
September 2022, Volume 40, Issue 9, Pages 408.e9-408.e18; doi: 10.1016/j.urolonc.2022.06.002
Clinical validation of IsoPSA, a single parameter, structure-focused assay for improved detection of prostate cancer: A prospective, multicenter study Eric A. Klein, Alan Partin, Yair Lotan, Jack Baniel, Martin Dineen, Jason Hafron, Kannan Manickam, Marc Pliskin, Matthew Wagner, Aimee Kestranek, Mark Stovsky
Objective Methodology
To validate the diagnostic performance of IsoPSA for clinically significant prostate cancer (csPCa) risk on biopsy in men age ≥ 50 with total PSA ≥ 4 ng/mL. 5-year prospective, multicenter study of 888 men scheduled for prostate biopsy at eight academic and community medical centers. Estimate the overall performance characteristics of IsoPSA to identify the risk of csPCa; Compare the diagnostic accuracy of IsoPSA to total PSA and % free PSA; evaluate subgroups (total PSA 4-10 ng/mL, total PSA >10 ng/mL, biopsy naïve, prior negative biopsy).
Results
IsoPSA outperformed total PSA and % free PSA on area under the ROC curve, specificity, and positive and negative predictive values at similar sensitivity. Using the IsoPSA Index cutoff for csPCa (>6), an estimated 46% of biopsies could be avoided in low-risk patients. IsoPSA Index (>6)
Total PSA (>4 ng/mL)
% Free PSA (≤25%)
Sensitivity*
90.2%
93.1%
94.7%
Specificity
45.5%
20.2%
13.7%
PPV
47.7%
36.1%
38.2%
NPV
89.3%
85.8%
82.0%
AUC
0.783
0.672
0.724
n (population): IsoPSA Index = 888 | Total PSA = 1112 | % Free PSA = 938 Prevalence for csPCa: IsoPSA Index = 0.356 | Total PSA = 0.326 | % Free PSA = 0.360 *Differences in sensitivity are not statistically significant
Conclusion
IsoPSA diagnostic performance and predictive value is validated for csPCa in men age ≥50 with total PSA ≥4 ng/mL undergoing diagnostic biopsy. IsoPSA outperforms total and % free PSA in discriminating the risk of prostate cancer on biopsy.