Evaluating the diagnostic value of free-to-total PSA ratio for clinically significant prostate cancer in the MRI era - a multicentre analysis.

Abstract

Introduction & Objectives: The freeto-total prostate-specific antigen (F/T PSA) ratio has traditionally been used as an adjunct to total PSA between 4 and 10 ng/mL. However, with the wide utilisation of MRI, the role of F/ T PSA is unclear. We aim to assess the diagnostic utility of the F/T PSA ratio in predicting clinically significant prostate cancer (csPCa) in the MRI era. Method(s): Patients who had a new diagnosis of prostate cancer at two tertiary centers between 2016 and 2023 with MRI and PSA F:T ratio, prior to prostate biopsy were identified. Demographic, biopsy, and PSA-related parameters (F/T ratio, free PSA, and PSA density) were collected. Diagnostic performance was evaluated using receiver operating characteristic (ROC) curve analysis, and Area Under the Curve (AUC) comparisons. Result(s): A total of 603 patients were included. Among them, 393 (65.2%) had a PI-RADS 4/5 lesion, 146 (24.2%) had a PI-RADS 1-3 lesion, and 64 (10.6%) did not have MRI. Clinically significant prostate cancer (csPCa) was detected in 174 men (44.3%) with a PI-RADS 4/5 lesion and in 38 men (26.0%) with a PIRADS 1-3 lesion. 299 (49.6%) patients had a PSA <10 with 20.6% (n = 124) having a F:T ratio of >15 and 32.8% (n = 200) <15. Of the 124 (20.6%) patients who had a total PSA of <10 and free-to-total (F:T) ratio <15%, 89 (71.8%) were diagnosed with csPCa, while 35 (28.2%) had ISUP Grade Group 1 prostate cancer. For the detection of csPCa, MRI demonstrated a sensitivity of 79.4%, specificity of 40.5%, positive predictive value (PPV) of 10.8%, and negative predictive value (NPV) of 95.6%. Using an F:T ratio <15% yielded a sensitivity of 50.0%, specificity of 63.6%, PPV of 11.1%, and NPV of 93.4% (given a csPCa prevalence of 8.3%). The area under the curve (AUC) for MRI was 0.609 (P < 0.04), while the AUC for an F:T ratio <15% was 0.54 (P = 0.75). Conclusion(s): Our results show that MRI outperforms the F:T PSA ratio in detecting csPCa, confirming its value in ruling out significant disease while highlighting the limited utility of F:T ratio as a standalone marker.