Risk Stratification by Prostate Health Index Prior to MRI-Ultrasound Fusion Targeted Biopsy
Benjamin Press, MD, Ghazal Khajir, MD, Michael S. Leapman, MD, Preston Sprenkle, MD.
Yale University School of Medicine, New Haven, CT.
BACKGROUND: Serum biomarkers that improve upon prostate specific antigen (PSA) for the prediction of prostate cancer, and may therefore help improve selection for prostate biopsy. Limited information exists to guide how these tools should be integrated in the context of prostate magnetic resonance imaging (MRI) in the MR-targeted biopsy era. We aimed to identify a biomarker threshold for the detection of GG2 or higher prostate cancer at MRI ultrasound fusion-targeted biopsy (MRF-TB).
METHODS: Between June 2015 and July 2019, 192 men received biomarker testing with the prostate health index (phi), a measurement that combines %free PSA, total PSA, and the -2proPSA isoform of PSA, prior to undergoing MRF-TB at our institution. Findings on prostate biopsy (including Grade Group [GG]), PI-RADS, and phi were prospectively recorded. Cancer detection rates (CDR) at pre-determined phi ranges were evaluated. The interaction of PI-RADS and phi was also evaluated at phi level of 27 (previously reported and widely used cutoff) versus the phi cutoff value calculated at our institution.
RESULTS: The median phi score was 51 (interquartile range 36-70). Sensitivity of phi for detecting any prostate cancer at a cutoff of 27 and 36 was 92.54% and 85.82%, respectively. Sensitivity of phi for detecting any GG2 or higher prostate cancer at a cutoff of 27 and 36 was 95.06% and 88.89%, respectively. In the subset of men with PSA between 4 and 10 ng/mL, CDR of GG2 and higher prostate cancer was significantly higher at a phi > 36 than < 36 (18.7 vs 47.8%, p =0.01) (Table 1) . Among all men who obtained phi prior to MRF-TB, no men who had PI-RADS ≤ 3 and a negative phi were found to have GG2 or higher prostate cancer both at phi cutoffs of 27 and 36 (Table 2).
CONCLUSIONS: We evaluated the performance of the prostate health index among patients with suspicion of prostate cancer undergoing MRI ultrasound fusion biopsy. This analysis supports the use of a phi cutoff of ≤ 36 to avoid biopsy among patients whose prostate MRI has a low suspicion for prostate cancer. 
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