Matthew Truesdale, MD, on IsoPSA performance with and without mpMRI

In the following interview, conducted at the 2026 American Urological Association Annual Meeting, Matthew Truesdale, MD, FACS, discusses findings from a validation analysis demonstrating the performance of IsoPSA both in patients undergoing prostate biopsy without pre-biopsy multiparametric MRI (mpMRI) and in those with mpMRI PI-RADS 1-3 lesions. Truesdale is a urologist at Advanced Urology Institute in Florida.

The analysis evaluated a subset of 566 patients from the larger prospective clinical validation study that supported FDA authorization of IsoPSA. Eligible patients were aged 50 years or older with a total PSA of 4 to 10 ng/mL who were undergoing early detection for prostate cancer. All participants received IsoPSA testing before biopsy, with both investigators and patients blinded to the results so that biopsy decisions were made independently of the biomarker. The investigators specifically examined IsoPSA performance in 2 contemporary clinical scenarios: patients without pre-biopsy mpMRI and those with mpMRI demonstrating PI-RADS 1-3 lesions, a population in which biopsy decisions are often less straightforward, Truesdale noted.

Truesdale explained that among the 362 patients who did not undergo pre-biopsy mpMRI, the prevalence of clinically significant prostate cancer (Grade Group 2 or higher) was 31.49%. Stratification by IsoPSA meaningfully altered post-test risk, however. Patients with an IsoPSA Index of 6 or lower had a 5.95% likelihood of clinically significant disease, whereas those with an IsoPSA Index greater than 10 had a 48.78% probability of harboring clinically significant cancer. Truesdale noted that these findings suggest a low IsoPSA result could provide greater confidence in continued surveillance rather than immediate biopsy, while higher scores identify patients at substantially increased risk.

A similar pattern was observed in the 204 patients with pre-biopsy mpMRI PI-RADS 1-3 findings. Although the overall prevalence of clinically significant prostate cancer in this subgroup was 19.12%, the post-test probability decreased to a 5.13% among patients with an IsoPSA Index of 6.0 or lower and increased to 31.03% among those with an IsoPSA Index greater than 10.0.

REFERENCE