Initial studies have shown that IsoPSA is more effective than total and percent-free PSA in detecting clinically significant prostate cancer (csPCa), classified as grade group (GG) ≥2 on biopsy. This biomarker could reduce the need for invasive testing and MRI in prostate cancer screening. This study retrospectively examined the predictive capacity of IsoPSA for csPCa by analyzing data from 1,578 patients tested with IsoPSA between November 2016 and August 2022. Patients were categorized based on baseline IsoPSA levels: normal (≤6) or high (>6). Outcomes such as follow-up IsoPSA and PSA results, prostate biopsy findings, MRI scans, and prostate cancer diagnoses were recorded. For individuals with multiple follow-ups, the most recent results were considered. Survival curves were generated to assess the predictive power of baseline IsoPSA for future csPCa development.
With a median follow-up of 24 months, the results indicated that among the 541 patients with a normal baseline IsoPSA, only 11.1% experienced a subsequent elevated IsoPSA, 4.3% were diagnosed with csPCa on follow-up biopsy, and 8.9% showed suspicious MRI findings (PI-RADS 4-5). In contrast, of the 1,037 patients with initially high IsoPSA, 35.3% were diagnosed with csPCa on biopsy, and 33% had suspicious MRI results. IsoPSA demonstrated a 94.1% sensitivity for predicting csPCa, with a negative predictive value of 89.3%. Within the 24-month period, patients with normal baseline IsoPSA had a 2.5% likelihood of csPCa development, whereas those with elevated IsoPSA faced a 29.9% risk. These findings suggest that a low baseline IsoPSA provides reliable information about a reduced two-year risk of csPCa, potentially sparing patients from unnecessary invasive procedures.
