Abstract 2546: Predictive value of prostate health index (PHI) in multi-parametric MRI in an ethnically diverse cohort
Authors: Carbunaru Samuel , Babajide Rilwan , Schaeffer Edward M. , Gann Peter H. , Murphy Adam B. 
Published: July 2021

Introduction and Objective: The low specificity of PSA in prostate cancer (PCa) screening has caused excessive biopsies and over-detection of PCa. The multi-parametric MRI (mpMRI) with its Prostate Imaging Reporting and Data Systems (PIRADS) score have emerged as an important tool to enhance detection of clinically significant PCa, i.e. Gleason grade group (GG) 2-5 PCa. Use of serum-based biomarkers, such as the Prostate Health Index (PHI), may be useful adjuncts to patients with lesions identified on mpMRI in detecting GG2-5 PCa and determining who would most benefit from a prostate biopsy. No study to date has investigated whether PHI improves accuracy of mpMRI in detecting GG2-5 PCa in biopsy-naïve men nor with adequate representation of Black men. The objective of this study was to determine the utility of PHI as a secondary reflex test to mpMRI in improving the accuracy for detecting GG2-5 PCa and improving specificity in a multi-ethnic biopsy-naïve population.

Methods: From February 2017-2020, 143 men who were referred to participating urology clinics for elevated PSA levels were recruited into this prospective study and underwent both mpMRI and prostate biopsy. Enrolled men had to be between the ages of 40-79 years and prostate biopsy naïve to participate. Men with a history of a previous prostate cancer were excluded from the study. The mpMRI studies were blinded and read by two highly experienced genitourinary radiologists based on the standardized PIRADS criteria version 2.0. Logistic regression models were used to generate receiver operating characteristic curves. Models were tested for effect modification between Race and PHI and Race and PIRADS to determine if race impacted the prediction accuracy of either tool. The sensitivity, specificity, and predictive values of PHI thresholds were calculated by PIRADS scores. The primary outcome was GG2-5 PCa on biopsy, defined as any Gleason score ≥3+4.

Results: The study included 143 men, of which 65 (45.5%) identified as Black. Median age was 62.0 years and 55 men (38.4%) had GG2-5 PCa. PIRADS risk groups were as follows: 18.1% PIRADS 1-2, 32.9% PIRADS 3, and 49.0% PIRADS 4-5. For the logistic regression models developed, the interactions between PIRADS and Race (p=0.08) and Log(PHI) and Race (p =0.17) variables were not statistically significant. A PHI score of ≥49 prevented unnecessary biopsies in 55% of men and missed zero cases of GG2-5 PCa, yielding a positive predictive value of 32.6% and negative predictive value of 100%. There was no reliable PHI threshold to exclude PCa biopsies in PIRADS 1-2 or 4-5.

Conclusion: PHI and mpMRI of the prostate are independent predictors that aid in the detection of GG2-5 PCa in a Black enriched prostate biopsy cohort. PHI is particularly useful in men with equivocal PIRADS 3 lesions where a threshold of &gt;49 safely avoids over 55% of unnecessary biopsies without missing GG2-5 PCa in our cohort.

Citation Format: Samuel Carbunaru, Rilwan Babajide, Edward M. Schaeffer, Peter H. Gann, Adam B. Murphy. Predictive value of prostate health index (PHI) in multi-parametric MRI in an ethnically diverse cohort [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2546.