Abstract 5315: Mapping tumor infiltrating lymphocytes in whole prostatectomy specimens to visualize and quantify the immune microenvironment of prostate cancer

Abstract Background: Prostate cancer (PCa) frequently presents as multifocal lesions with histologic and molecular heterogeneity. A comprehensive understanding of tumor immune responses within the context of the complex PCa microenvironment remains elusive. Through the use of Digital Pathology and innovative Pathomics image analysis tools, tumor infiltrating lymphocytes (TILs) can be mapped, visualized, and quantified in whole slide images (WSIs) of H&E stained PCa slides. We have developed a novel workflow to map and quantify TILs by Gleason histologic grade (Gleason-TIL maps) in whole radical prostatectomy specimens. Approach: WSIs from 211 H&E tissue sections from eight whole radical prostatectomy specimens containing Gleason histologic patterns 3 and 4 were used in the development of the PCa Pathomics workflow. Pathomics tools generated PCa Tumor-TIL and Gleason-TIL maps for each corresponding H&E WSI for all eight prostatectomy specimens. To support tissue sampling for correlative biomarker studies and genomic testing in PCa clinical trials, each Tumor-TIL and Gleason-TIL map was partitioned to quantify total PCa content, Gleason grade (3 vs 4/5) content, and intratumoral and peritumoral TILs per 0.5 x 0.5 cm area tile of tissue in the WSI. Results: Both Tumor-TIL and Gleason-TIL maps reveal complex and heterogeneous tumor immune interactions across multifocal lesions within each radical prostatectomy specimen. Our novel workflow added the ability to quantify PCa, Gleason grade, and TILs to specific 0.5 x 0.5 cm tissue tiles to quantify TILs relative to Gleason grade that varies within and across each case of multifocal PCa. Quantification of the TIL tile maps showed that in 6 of the 8 prostatectomies the “hot spot” tile with the most intratumoral TILs had more TILs in the Gleason 4/5 patches than in the adjacent Gleason 3 patches. Conclusionsand Future Studies: This novel workflow was developed to generate Tumor-TIL and Gleason-TIL maps for every PCa H&E WSI to serve as powerful visual tools for real world laboratory tissue sampling for downstream genomics, immunohistochemistry, and other correlative studies for PCa clinical trials. Adding a 0.5 x 0.5 cm tile partitioning function increases the efficiency of identifying and quantitatively mapping TILs in the complex and heterogeneous PCa microenvironment. The preliminary association of TILs with higher grade Gleason 4/5 PCa appears provocative as potential actionable information as an immune biomarker in PCa. Citation Format: Yuwei Zhang, Rajarsi Gupta, Joel Saltz, Tahsin Kurc, Jakub Kaczmarzyk, Erich Bremer, Veronica Wallaengen, Amanda Galvez, Abigail Bartley, Leonard Salcedo, Alan Pollack, Sanoj Punnen, Oleksandr Kryvenko, Radka Stoyanova, Sandra M. Gaston. Mapping tumor infiltrating lymphocytes in whole prostatectomy specimens to visualize and quantify the immune microenvironment of prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5315.