Abstracts from the Abstracts from the Mid-Atlantic Section of the AUA 2021

MA-AUA 2021 Abstracts Display Posters Comparison of Highest Grade Tumor Percentage in Core Samples from MRI-targeted Biopsy and Systematic Biopsy for Prostate Cancer Diagnosis A. Park, S. Wang, A. Van Besien, A. Lee, L. Xu, M. Naslund, M. Siddiqui University of Maryland School of Medicine, Baltimore, MD, USA Introduction and Objective: The advent of magnetic resonance imaging (MRI)-targeted biopsy(TB) has allowed for higher rate of detection of clinically significant prostate cancers than systematic biopsy(SB). However, it remains to be demonstrated if the improved targeting also leads to more accurate representation of tumor volume by sampling the center, rather than periphery, of the tumor nodule. This study aims to compare the two biopsy methods in its ability to detect a higher percentage of the highest grade tumor in core samples. Methods: We examined the biopsy reports of patients who underwent prostate cancer biopsy from 2015 to 2020. A total of 411 patients with MRI- visible prostate lesions received both MRI-TB and SB. The core samples with the highest Gleason scores were isolated for each biopsy method, followed by identification of the corresponding maximum percentage tumor. T-test was performed comparing the maximum tumor percentages for the highest Gleason scores between MRI-TB and SB. Results: Of the 411 patients, those with benign biopsy results for both TB and SB were excluded, resulting in 213 (51.8%) patients for analysis. The TB demonstrated an equal or greater % tumor in the highest biopsy core in 166 (77.9%) of cases. In cases where SB % tumor was >TB % tumor, 42 cases were due to no tumor on TB, and 5 cases (2%) were TB<SB. Overall, the mean maximumpercentage of tumor in the core with the highest Gleason score was higher for TB vs. SB (45.1% vs. 35.4%, p=0.009). This reflects a 27% increase in diagnosed tumor diameter, and 2.1-fold increase in inferred tumor volume. Conclusions: In men that underwent both MRI-TB and SB, the TB more accurately captured prostate cancer tumor volume. DP-09 Active Surveillance or Watchful Waiting in Clinically Low-Risk Prostate Cancer Patients in the SEER Database With and Without an Oncotype DX Genomic Prostate Score Assay Y. Yuan 1 , V. Petkov 1 , T. Aboushwareb 2 , J. Bennett 2 , G. Fermin 2 , A. Akkunuri 2 , Z. Cheung 2 , S. Gomez 3 , I. Cheng 3 , N. Schussler 4 , S. Negoita 4 , S. Shak 2 1 Surveillance Research Program, Division of Cancer Control and Population Sciences, National Cancer Institute, Rockville, MD, USA; 2 Exact Sciences Corporation, Redwood City, CA, USA; 3 University of California, San Francisco, San Francisco, CA, USA; 4 Information Management Services, Calverton, MD, USA Introduction and Objective: The Surveillance, Epidemiology, and End Results (SEER) Program collects cancer data on approximately 35% of the US population. The Oncotype DX Genomic Prostate Score® (GPS™) assay is used to help guide treatment decisions at prostate cancer diagnosis. We linked data from the SEER registries with results from the GPS assay and evaluated determinants of selection of active surveillance/watchful waiting (AS/WW) for patients diagnosed with localized clinically low-risk prostate cancer. Methods: The SEER data were restricted to patients diagnosedwith localized prostate cancer from 2013 through 2017 and linked to GPS data from 2013 through 2018. Eligible patients were classified into NCCN risk groups using clinical variables. We usedmultivariable logistic regression to identify factors associated with selecting AS/WW as initial management. Results: 120,223 patients were included. Median age was 64 years, 70%were white, and 44% were NCCN Very Low/Low, 27% Favorable Intermediate, 22% Unfavorable Intermediate, and 7% Unknown Intermediate risk. AS/ WWpercentages increased by year, from 18.3% (95% CI: 17.8, 18.8) in 2013 to 27.1% (26.5, 27.7) in 2017. Among the 5,553 (4.6%) patients with a GPS result 48.8% (47.5, 50.1) had AS/WW, compared to 21.6% (21.3, 21.8) with no GPS result (p < 0.001). The percentage of patients on AS/WW decreased as the GPS result increased: 58.3% (56.1, 60.4) for GPS results 0-20, 47.4% (45.6, 49.3) for 21-40, and 27.1% (23.8, 30.6) for >40. In a multivariable logistic regression model that included age, race/ethnicity, year of diagnosis, and NCCN risk group, receiving a GPS result (vs no GPS result) was associated with AS/ WW selection (OR 2.7 [95% CI 2.5, 2.9], p < .001). Conclusions: While overall use of AS/WW increased from 2013 to 2017, the GPS assay was independently associated with AS/WW, after adjusting for year of diagnosis and other covariates. DP-08 49