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Investigating outcomes in patients with PI-RADS 5 lesions and no clinically significant prostate cancer: is immediate treatment the right response?
Constantine S. Velmahos, BS1, Alexandra Hunter, BS2, Clemens An, BS3, Doug M. Dahl, MD2, Michelle M. Kim, MD, PhD2, Shulin Wu, MD, PhD2, Matthew Wszolek, MD2, Keyan Salari, MD, PhD2, Dimitar Zlatev, MD2, Mukesh Harisinghani, MD2, Chin-Lee Wu, MD, PhD2, Adam S. Feldman, MD, MPH2.
1University of Massachusetts T.H. Chan Medical School, Worcester, MA, USA, 2Massachusetts General Hospital, Boston, MA, USA, 3University of Vermont Larner College of Medicine, Burlington, VT, USA.

BACKGROUND: The Prostate Imaging Reporting and Data System (PI-RADS) score is a useful, predictive tool in analyzing suspicious prostate lesions on multi-parametric magnetic resonance imaging (mpMRI). Higher PI-RADS scores are associated with increased risk of clinically significant prostate cancer (csPCA). However, the management of PI-RADS 5 patients with no-csPCA is uncertain, given the possibility of false negative prostate biopsy versus false positive radiographic result. Our objective is to describe the outcomes of patients with PI-RADS 5 lesions but no-csPCA detected on transrectal ultrasound-guided (TRUS) fusion+standard template prostate biopsy.
METHODS: Patients who underwent mpMRI and TRUS fusion biopsy between February 2014 and June 2022 at an academic, tertiary-care center were retrospectively reviewed. Biopsies with all benign findings or Grade Group (GG) 1 prostate cancer on fusion and/or standard cores were classified as no-csPCA. Patients with PI-RADS 5 lesion(s) and no-csPCA were subsequently included. Patient demographics, laboratory and imaging data, operations, and follow-up care were recorded.
RESULTS: Of 1,817 patients in the database, 542 had a PI-RADS 5 lesion, of which 163 (30.0%) had no-csPCA on biopsy. Of these patients, 115 (70.5%) and 48 (29.5%) were found to have GG1 and benign findings, respectively. The indications for mpMRI and biopsy in 84 (51.5%), 42 (25.8%), 33 (20.2%), and 4 (2.4%) patients was elevated prostate specific antigen (PSA) with no prior biopsy, low-risk prostate cancer on active surveillance, elevated PSA with prior negative biopsy, and abnormal digital rectal exam, respectively. Notably, of 33 individuals with a previous negative biopsy, 19 continued to have benign findings on biopsy.
Table 1 describes the follow-up interventions in this cohort. Of those with GG1, 57 continued to immediate radical prostatectomy or radiation, while 50 were monitored with active surveillance. PSA density (PSAd) was higher in the former sub-group (0.21+0.1 vs 0.16+0.11, p=0.04, for immediate treatment vs active surveillance, respectively).
Table 2 summarizes the imaging results in the patients with repeat mpMRI and Table 3 outlines the pathologic outcomes in the sub-group of repeat biopsy and radical prostatectomy. Notably, on repeat mpMRI, 35.5% of patients had lower PI-RADS score or disappearance of lesion, while 75.8% patients had no-csPCA on repeat biopsy.
CONCLUSIONS: Despite no csPCA on biopsy, one-third of patients with PI-RADS 5 lesions underwent radical prostatectomy or radiation, suggesting a high PI-RADS score and PSAd weigh heavily in clinical decision-making. However, a significant proportion of patients show disappearance of lesion on repeat MRI and a majority show non-worsening results on repeat biopsy. Further research is needed to identify the subgroup of PI-RADS 5 patients with GG1 who require immediate treatment.

Table 1: Outcomes of patients with >1 prior PI-RADS 5 lesion and no csPCA on fusion TRUS biopsy.
Observation/Active Surveillance91 (55.8%)
-Repeat PSA only38 (23.3%)
-Repeat biopsy and PSA8 (4.9%)
-Repeat mpMRI and PSA21 (12.8%)
-Repeat mpMRI, biopsy, and PSA24 (14.7%)
Immediate Treatment57 (34.8%)
-Radical Prostatectomy33 (20.1%)
-Radiation Therapy24 (14.7%)
Lost to follow-up15 (9.2%)

Table 2: Outcomes of patients with >1 prior PI-RADS 5 lesion and no csPCA on fusion TRUS biopsy.
Lesion Classification
-No Suspicious Lesion11 (24.4%)
-PIRAD 21 (2.2%)
-PIRAD 31 (2.2%)
-PIRAD 43 (6.7%)
-PIRAD 529 (64.4%)
Mean months to repeat MRI (SD)15.1 (6.5)

Table 3: Results of repeat biopsy and radical prostatectomy in patients with PI-RADS 5 and no-csPCA
Gleason Classification
-No cancer6 (18.2%)N/A
-GG118 (56.2%)15 (45.5%)
-GG27 (21.2%)16 (48.5%)
-GG51 (3.0%)2 (6%)
Mean months to intervention (SD)14.3 (6.8)4.7 (5.3)

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