Source of Funding: None MP28-18 PROSTATE HEALTH INDEX DENSITY SIGNIFICANTLY IMPROVES THE ACCURACY OF PREDICTING CLINICALLY SIGNIFICANT PROSTATE CANCER IN MEN UNDERGOING PROSTATE BIOPSY Yung Ting Cheng*, Shih Ting Chiu, Chih-Hung Chiang, Chung-Hsin Chen, Yeong-Shiau Pu, Jian-Hua Hong, Yu-Chuang Lu, Yi-Kai Chang, Shih-Ping Liu, Shih-Chun Hung, Hong-Chiang Chang, Po-Ming Chow, Kuo-How Huang, Yuan-Ju Lee, Chao-Yuan Huang, Taipei City, Taiwan INTRODUCTION AND OBJECTIVES: Prostate health index (PHI) is a promising biomarker in the prediction of aggressive prostate cancer. Since prostate volume has been regarded as an important factor contributing to elevated prostate-specific antigen (PSA), PSA density is widely used to predict the presence of prostate cancer. We aim to assess the additional efficacy of PHI density (PHID) in predicting prostate cancer in men undergoing transrectal ultrasound- guided prostate biopsy (TRUSP biopsy). METHODS: We prospectively enrolled 505 men who under- went TRUSP biopsy for suspected prostate cancer. Total PSA, free PSA, p2PSA levels were measured by serum samples before the prostate biopsy. PHI was calculated as ((p2PSA/fPSA)  OtPSA). PHID was calculated by diving PHI by the prostate volume. Receiver oper- ating characteristic curve (ROC curve) and multivariable logistic regression analyses were used to predict the risk of cancer detection and clinically significant prostate cancer. RESULTS: The detection rate of prostate cancer was 33.1% (167/505). 65.8% (110/167) of the cancer patients were found to have Gleason score 7 or higher disease. Prostate volume, total PSA, free PSA, p2PSA, p2PSA%, and PHI in cancer cases were significantly higher than the non-cancer patients. The median PHI in both cancer and non-cancer men were 50.93 and 29.79, respectively; whereas the PHID were 1.61 and 0.58, respectively. PHID had the highest area under the ROC curve (AUC) in predicting the presence of prostate cancer and clinically significant cancer than other predictors (0.806 and 0.865, both p<0.001). At a threshold of 0.71, PHID had a sensitivity of 91.7% and a specificity 59.3% for clinically significant cancer. In multivariable logistic regression, age, prostate volume, total PSA and PHID were significant predictors of clinically significant cancer. CONCLUSIONS: Utilizing prostate volume adds discriminative value to PHI in predicting clinical significant prostate cancer. Unnecessary biopsies could be avoided by using PHID as an alterna- tive to PSA test. Source of Funding: None MP28-19 SETTING THE BAR: A 4KSCORE OF 7.5% PROVIDES HIGH SENSITIVITY AND NEGATIVE PREDICTIVE VALUE FOR DETECTING AND RULING OUT SIGNIFICANT PROSTATE CANCER Amit Bhattu*, Miami, FL; Yan Dong, Woburn, MA; Alexander Kong, Miami, FL; Stephen Zappala, Andover, MA; Dipen Parekh, Sanoj Punnen, Miami, FL INTRODUCTION AND OBJECTIVES: Two independent pro- spective trials have validated the 4Kscore test for predicting clinically significant cancer. However, they assessed the 4kscore test as a continuous score. We wanted to illustrate the use of a 7.5% cut off for deciding on the need for prostate biopsy using combined data from both trials. METHODS: This study pooled data from two prospective multi- institutional trials. One was conducted in 26 primarily community-based U.S. urology practices and the other was conducted at 8 U.S. Veterans Affairs Medical Centers. Men in both the trials were 40-80 years old and referred for biopsy of the prostate. A minimum 10-core biopsy was required, and phlebotomy was done before for 4Kscore ascertainment. The primary outcome was presence of Gleasons score  7 on biopsy. We performed exploratory analysis to evaluate the number of biopsies avoided and cancers detected using a 4Kscore cut off of 7.5% using the entire cohort, and various subgroups. RESULTS: This analysis included 1378 patients who had a 4Kscore and biopsy, of which 1012 patients were from the original validation study and 366 were from Veterans Affairs study. The analysis showed that 32.2% of biopsies would have been avoided by applying a 4Kscore threshold of 7.5% for prostate biopsy. The sensitivity for detecting Gleason  7 cancer using a 7.5% cut-off was 94%, while the negative predictive value for ruling it out was 95%. There were no Gleason 8 or higher prostate cancers missed when using this cut off for proceeding with a biopsy. Among patients with a 4Kscore less than 7.5%, prostate biopsy findings were benign in 76.1% patients, revealed a Gleason 6 in 19.1%, Gleason 3þ4[7 in 3.4% patients, and Gleason 4þ3[7 in 1.4% patients (Figure 1). Subgroup analyses in patients with a PSA between 3-10ng/ml, and between African American and non-African American men revealed no difference in the risk of significant cancer in those with a 4Kscore below 7.5%. CONCLUSIONS: The 4Kscore is noninvasive biomarker that helps to facilitate biopsy decision-making. We found that using a 7.5% cut-off allowed a significant biopsy reduction with high sensitivity for detection, and a high negative predictive value for ruling out aggressive prostate cancer. Vol. 201, No. 4S, Supplement, Saturday, May 4, 2019 THE JOURNAL OF UROLOGY Ò e411 Copyright © 2019 American Urological Association Education and Research, Inc. Unauthorized reproduction of this article is prohibited.