IsoPSA prostate cancer diagnostic capabilities-By Adebowale Awosika-Olumo, MD., MS., MPH, PhD., FACE

IsoPSA is an innovative blood-based test designed to improve the accuracy of prostate cancer diagnosis and reduce unnecessary biopsies. Here’s an overview of its diagnostic capabilities and clinical impact.

How IsoPSA Works

Unlike traditional PSA tests that measure the concentration of prostate-specific antigen, IsoPSA analyzes the structural isoforms of PSA, which are more closely linked to cancer-specific changes. This structure-based approach allows IsoPSA to better distinguish between benign conditions and clinically significant prostate cancer(Klein et al., 2017; Klein et al., 2022; Stovsky et al., 2019).

Diagnostic Accuracy

Multiple large, prospective studies have validated IsoPSA’s superior performance compared to total PSA and percent free PSA. IsoPSA consistently shows higher accuracy in detecting both any prostate cancer and high-grade (clinically significant) prostate cancer, with area under the ROC curve (AUC) values around 0.78–0.81 for high-grade disease(Klein et al., 2022; Stovsky et al., 2019; Klein et al., 2017). This means IsoPSA is more reliable at identifying patients who truly need further intervention.

Reducing Unnecessary Biopsies

One of IsoPSA’s most significant benefits is its ability to reduce unnecessary prostate biopsies. Studies show that using IsoPSA as a decision tool can cut the number of unneeded biopsies by 42–55% without missing a substantial number of high-grade cancers(Klein et al., 2022; Stovsky et al., 2019; Klein et al., 2017; Scovell et al., 2021; Hettel et al., 2021). This not only spares patients from invasive procedures but also reduces healthcare costs and the risk of biopsy-related complications(Lotan et al., 2020).

Predictive Value and Long-Term Risk Assessment

IsoPSA demonstrates high sensitivity (94–95%) and negative predictive value (89–95%) for clinically significant prostate cancer, meaning a low IsoPSA result reliably indicates a low risk of aggressive disease over at least 18–24 months of follow-up(Abdallah et al., 2024; Abdallah et al., 2023). Patients with low IsoPSA rarely develop significant cancer in the short to medium term, supporting its use in active surveillance strategies.

Integration with MRI and Other Biomarkers

Combining IsoPSA with prostate MRI (PI-RADS scoring) further refines risk assessment. Patients with both a low IsoPSA and negative MRI have a very low probability (<5%) of clinically significant cancer, potentially allowing many to safely avoid biopsy(Benidir et al., 2023; Benidir et al., 2023). Conversely, elevated IsoPSA and adverse MRI findings together indicate a much higher risk, guiding more targeted intervention.

Clinical Utility and Real-World Impact

IsoPSA has been rapidly adopted in diverse clinical settings, with strong concordance between test results and provider recommendations. Its use leads to substantial reductions in both biopsy and MRI recommendations, streamlining patient management and improving the risk-benefit ratio of prostate cancer screening(Scovell et al., 2021; Hettel et al., 2021).

Conclusion

IsoPSA represents a major advance in prostate cancer diagnostics, offering improved accuracy, fewer unnecessary biopsies, and better patient outcomes compared to traditional PSA testing. Its integration with imaging and other biomarkers further enhances its clinical value.

References

Klein, E., Chait, A., Hafron, J., Kernen, K., Manickam, K., Stephenson, A., Wagner, M., Zhu, H., Kestranek, A., Zaslavsky, B., & Stovsky, M. (2017). The Single-parameter, Structure-based IsoPSA Assay Demonstrates Improved Diagnostic Accuracy for Detection of Any Prostate Cancer and High-grade Prostate Cancer Compared to a Concentration-based Assay of Total Prostate-specific Antigen: A Preliminary Report.. European urology, 72 6, 942-949. https://doi.org/10.1016/j.eururo.2017.03.025

Abdallah, N., Benidir, T., Wood, A., Lone, Z., Campbell, R., Zhang, A., Ergun, O., Curry, C., Liao, R., Michael, P., Haywood, S., Schwen, Z., Olivares, R., Kaouk, J., Abouassaly, R., Klein, E., & Weight, C. (2024). The risk of prostate cancer diagnosis in men with an elevated PSA but low IsoPSA.. Journal of Clinical Oncology. https://doi.org/10.1200/jco.2024.42.4_suppl.292

Klein, E., Partin, A., Lotan, Y., Baniel, J., Dineen, M., Hafron, J., Manickam, K., Pliskin, M., Wagner, M., Kestranek, A., & Stovsky, M. (2022). Clinical validation of IsoPSA, a single parameter, structure-focused assay for improved detection of prostate cancer: A prospective, multicenter study.. Urologic oncology. https://doi.org/10.1016/j.urolonc.2022.06.002

Stovsky, M., Klein, E., Chait, A., Manickam, K., Stephenson, A., Wagner, M., Dineen, M., Lotan, Y., Partin, A., Baniel, J., Kestranek, A., Gawande, P., & Zaslavsky, B. (2019). Clinical Validation of IsoPSA™, a Single Parameter, Structure Based Assay for Improved Detection of High Grade Prostate Cancer. The Journal of Urology, 201, 1115–1120. https://doi.org/10.1097/JU.0000000000000185

Abdallah, N., Benidir, T., Lone, Z., Zhang, A., Wood, A., Curry, C., Haywood, S., Kaouk, J., Abouassaly, R., Klein, E., & Weight, C. (2023). The natural progression of patients with an IsoPSA value and its predictive ability of clinically significant prostate cancer on biopsy.. Journal of Clinical Oncology. https://doi.org/10.1200/jco.2023.41.6_suppl.325

Benidir, T., Lone, Z., Abdallah, N., Wood, A., Campbell, R., Purysko, A., Nguyen, J., Klein, E., Abouassaly, R., Campbell, S., & Weight, C. (2023). Use of IsoPSA with prostate MRI PIRADS score in biopsy decision making in patients with elevated PSA.. Journal of Clinical Oncology. https://doi.org/10.1200/jco.2023.41.6_suppl.388

Benidir, T., Lone, Z., Wood, A., Abdallah, N., Campbell, R., Bajic, P., Purysko, A., Nguyen, J., Kaouk, J., Haber, G., Eltemamy, M., Stein, R., Haywood, S., Klein, E., Almassi, N., Campbell, S., Abouassaly, R., & Weight, C. (2023). Using IsoPSA with PI-RADS Score May Help Refine Biopsy Decision Making in Patients with Elevated PSA.. Urology. https://doi.org/10.1016/j.urology.2023.03.014

Lotan, Y., Stovsky, M., Rochelle, R., & Klein, E. (2020). Decision Analysis Model Comparing Cost of IsoPSA™ vs Repeat Biopsy for Detection of Clinically Significant Prostate Cancer in Men with Previous Negative Findings on Biopsy.. Urology Practice. https://doi.org/10.1097/UPJ.0000000000000142

Scovell, J., Hettel, D., Abouassaly, R., Almassi, N., Berglund, R., Breaux, T., Weight, C., Isac, W., Zampini, A., Stark, E., Rochelle, R., Kestranek, A., Stovsky, M., & Klein, E. (2021). IsoPSA® Reduces Provider Recommendations for Biopsy and Magnetic Resonance Imaging in Men with Total Prostate Specific Antigen ≥4 ng/ml: A Real-World Observational Clinical Utility Study. Urology Practice, 9, 174 – 180. https://doi.org/10.1097/UPJ.0000000000000291

Hettel, D., Kestranek, A., Rochelle, R., Stovksy, M., & Klein, E. (2021). MP05-20 ISOPSA SUBSTANTIALLY REDUCES UNNEEDED BIOPSIES IN A REAL-WORLD OFFICE SETTING. The Journal of Urology, 206, e87 – e87. https://doi.org/10.1097/JU.0000000000001972.20