Abstract Background: With the recent advancement in perioperative treatment protocols, the search for clinical biomarkers that can predict overall response and long-term cancer outcome independent from treatment acquires even more importance. Recently, it has become clear that mechanical properties of the tumor microenvironment in solid tumors play a key role in driving outcome, mediating immune infiltration and activation, and response to therapy. Moreover, a growing body of evidence supports the understanding that mechanical changes induced by a plethora of therapeutic regimens should be leveraged to elicit favorable outcome. Methods: In this work we propose a dual approach to reveal mechanical biomarkers predictive of long-term outcome in solid cancers. Our first approach is based on a newly developed, 60 channel, biomechanical imaging mass cytometry panel to elucidate biomechanical cues that drive tumor aggressiveness and immune infiltration. Our second approach utilizes the AFM-based Automated and Reliable Tissue Diagnostics (ARTIDIS) investigational device to measure mechanical properties of fresh clinical biopsy samples at a nanoscale resolution. Our analysis was performed on over 300 clinical samples, from routine baseline clinical biopsies collected from both the Breast Clinic, University Hospital Basel, and the University of Dundee, in the UK. Patients in these two cohorts were treated with either adjuvant or neoadjuvant approaches, including radiation, chemotherapy, hormonal, and surgical treatment regimens, with individual patient follow up as long as 20 years. Results: We demonstrated with two complimentary technologies that biomechanical spatial patterns drive outcome in breast cancer. Our results include a multi-platform elucidation of the biomechanical phenotypes of epithelial to mesenchymal transitions driven by hypoxic environments. Furthermore, we identified several biomechanical subpopulations of cancer associated fibroblasts, and their role in mediating cancer outcome, in relationship with survival time and several clinical variables (e.g. metastasis, nodes, grade). We mechanistically corroborated these results by evaluating the immune modulatory effect of the identified biomechanical microenvironments in breast cancer. Lastly, we correlated the identified biomechanical microenvironments with the ARTIDIS nanomechanical signature as a clinically integrated, rapid, single biomechanics signature at the nanoscale. Conclusion: Our results further validate the importance of biomechanics in driving tumor response and immune infiltration across a variety of clinical treatment setting. These result support the integration of ARTIDIS nanomechanical signature in clinical settings as a single predictive biomarker able to rapidly and accurately capture biomechanical alterations that drive cancer outcome. Citation Format: Sara Nizzero, Maria Pelaez Soni, Gregory Zaugg, Yitian Xu, Licheng Zhang, Junjun Zheng, Lee B. Jordan, Colin A. Purdie, Philip R. Quinlan, Chandandeep Nagi, Karla A. Sepulveda, Philipp Oertle, Tobias A. Appenzeller, Marko Loparic, Shu-Hsia Chen, Vittorio Cristini, Marija Plodinec, Alastair M. Thompson. A multimodal, spatially defined, nanomechanical signature as predictive biomarker for breast cancer outcome: A 20 year survival study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5185.