What question did this study set out to answer?

To evaluate the impact of neoadjuvant atezolizumab on the tumor microenvironment in operable urothelial carcinoma.

April 5, 2026

Abstract 6668: Spatial and transcriptomic remodeling of the tumor microenvironment following neoadjuvant atezolizumab in urothelial carcinoma: Insights from the ABACUS Study

Key Points

To evaluate the impact of neoadjuvant atezolizumab on the tumor microenvironment in operable urothelial carcinoma.
Conducted a single-arm, phase II trial with paired baseline and post-treatment tumor specimens.
Performed bulk transcriptomic and immunohistochemistry analyses to identify treatment response biomarkers.
Utilized artificial intelligence-assisted digital image analysis and Visium spatial transcriptomics on tumor samples.
Post-treatment specimens exhibited significant tumor microenvironment remodeling with increased immune infiltration and stromal changes.
Alterations in the microenvironment were linked to different clinical outcomes, including stable disease versus relapse.
Highlighted the potential for spatial and phenotypic biomarkers to guide combination strategies in treatment-resistant cases.

Abstract

Abstract The ABACUS study was a single-arm, phase II trial evaluating neoadjuvant atezolizumab in operable urothelial carcinoma. Paired baseline and post-treatment tumor specimens were analyzed to identify biomarkers associated with treatment response. Initial bulk transcriptomic and immunohistochemistry analyses suggested links between immune activation, tissue remodeling and resistance pathways were associated with clinical outcome. To further characterize spatial and phenotypic changes at high resolution, artificial intelligence-assisted digital image analysis of hematoxylin however, robust tumor and endothelial activity may sustain immune exclusion and drive resistance despite immune expansion. Spatial and phenotypic biomarkers identified here may inform rational combination strategies for immune checkpoint inhibitor-refractory urothelial carcinoma. Citation Format: Robbin Nameki, Jennifer Kinong, Chao-Hui Huang, Michelle Saul, Aakash Sur, Mehmet Tekman, Alexander Trageser, Wenjing Yang, Daniel Chawla, Greg Szeto, Arne Schmidt, Alberto Megina Gonzalo, Srishti Munjal Mehta, Nina Kozar-Gillan, Rosemarie Krupar, Sophie Laturnus, Cornelius Bohm, Marija Pezer, Gloria H.Y. Lin, Diane Fernandez, Keith Ching, Jadwiga R. Bienkowska, Thomas Powles, Craig B. Davis. Spatial and transcriptomic remodeling of the tumor microenvironment following neoadjuvant atezolizumab in urothelial carcinoma: Insights from the ABACUS Study abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 6668.

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