RISKS OF GRADE RECLASSIFICATION AMONG PATIENTS WITH GLEASON GRADE GROUP 1 PROSTATE CANCER AND PI-RADS 5 FINDINGS ON PROSTATE MRI.

Most Prostate Imaging Reporting and Data System (PI-RADS) 5 lesions on prostate MRI are found to harbor Gleason grade group ≥2 prostate cancer on initial biopsy. As a result, the optimal management of patients found to have Gleason grade group 1 (GG1) prostate cancer despite PI-RADS 5 lesions on prostate MRI remains unclear. To estimate risks of grade misclassification, we evaluated the occurrence of Gleason upgrade on subsequent active surveillance (AS) prostate biopsy or radical prostatectomy among patients diagnosed with GG1 prostate cancer with PI-RADS 5 lesions on MRI. We conducted a retrospective analysis at a single institution to identify patients diagnosed with GG1 prostate cancer whose MRI nearest to diagnosis demonstrated ≥1 lesion classified as PI-RADS 5. The primary study outcome was the presence of Gleason reclassification to GG≥2 prostate cancer on subsequent prostate biopsy or radical prostatectomy. The secondary outcomes included rates of grade reclassification on prostate biopsy, or conversion to active treatment among patients managed with initial active surveillance. We used multivariable logistic regression to identify factors associated with Gleason reclassification on subsequent biopsy or radical prostatectomy. Among 3,042 patients undergoing prostate biopsy between 01/2013-12/2022, we identified 110 with GG1 prostate cancer and PI-RADS 5 lesions on;MRI who received a total of 216 biopsies. The median age was 69 years and median PSA at diagnosis was 6.4 ng/mL. There were 104 patients (94.6%) who elected initial AS and six (5.5%) were treated. Sixty-one patients managed with AS underwent ≥1 additional biopsy. Among this group, 43 (70.5%) experienced Gleason upgrade including 32 (74.4%) on second, 9 (20.9%) on third, and one (2.3%) each on fourth and fifth biopsy. A total of 44 (40%) patients received definitive treatment including prostatectomy in 15 (13.6%) and radiation in 25 (22.73%). Two patients (1.8%) developed metastatic disease, of whom one patient later demonstrated higher grade disease on biopsy, and one died of disease. In multivariable logistic regression, no clinical or pathological factors were significantly associated with odds of Gleason upgrade. The majority of patients diagnosed with GG1 prostate cancer in the setting of a PI-RADS 5 lesion will be found to have GG2 or higher disease in the short term during active surveillance or during treatment, suggesting substantial initial misclassification. These findings reinforce the need for confirmatory testing in these patients due to risks of disease under-sampling. [ABSTRACT FROM AUTHOR]