Protocol Intravital Microscopy (IVM) in Human Solid Tumors:Novel Protocol to Examine Tumor-Associated Vessels Denslow Allerton Trumbull 1 , BS; Riccardo Lemini 2 , MD; Sanjay P Bagaria 2 , MD; Enrique F Elli 2 , MD; Dorin T Colibaseanu 2 , MD; Michael B Wallace 3 , MD; Emmanuel Gabriel 4 , MD, PhD 1 College of Medicine, University of Florida, Gainesville, FL, United States 2 Department of Surgery, Mayo Clinic, Jacksonville, FL, United States 3 Department of Gastroenterology, Mayo Clinic, Jacksonville, FL, United States 4 Division of Surgical Oncology, Department of Surgery, Mayo Clinic, Jacksonville, FL, United States Corresponding Author: Emmanuel Gabriel, MD, PhD Division of Surgical Oncology Department of Surgery Mayo Clinic 4500 San Pablo Rd Jacksonville, FL, 32224 United States Phone: 1 904 953 2523 Email: Gabriel.Emmanuel@mayo.edu Abstract Background: Intravital microscopy (IVM) allows the real-time, direct visualization of microscopic blood vessels. This pilot clinical trial will elucidate the physical and functional characteristics of vessels associated with solid tumors. Objective: The main objective of this study is to determine the feasibility of performing IVM in patients with solid tumors during the standard course of surgical resection. IVM will also be performed when vasopressors or fluid boluses are administered during the standard course of the operation. Methods: This is an open-label, nonrandomized, single-center, pilot study of IVM observation in subjects with solid tumors undergoing surgical resection. Results: This study was active on January 1, 2019 (NCT03823144) and funded by the Mayo Clinic Florida Cancer Focused Research Team Award. As of September 27, 2020, we had enrolled 20 patients. Accrual period is expected to end by December 31, 2021. Conclusions: This trial will support the development of interventions to improve patient treatment by extending the application of IVM to the tumor microenvironment. IVM observations during volume and pressor management at the time of surgery may aid in the development of strategies to augment responses to systemic treatments. International Registered Report Identifier (IRRID): PRR1-10.2196/15677 (JMIR Res Protoc 2020;9(10):e15677) doi: 10.2196/15677 KEYWORDS intravital microscopy; solid tumors; microvasculature Introduction Intravital microscopy (IVM) is the microscopic observation of living tissue in real-time. IVM has been used to show that tumor vessels lack the sequential hierarchy of normal vessels such that arterioles, capillaries, and venules typically cannot be discriminated within tumor tissues [1,2]. This disorganization of aberrant tumor vessels was demonstrated in a previous clinical trial [3]. These tumor-associated vessels were also characterized by irregular diameters, aberrant branching patterns, abnormal blood flow rates, and anastomotic strictures. These characteristics could have profound influence on the delivery of agents (ie, chemotherapy or cellular immunotherapy) to the tumor microenvironment [4]. JMIR Res Protoc 2020 | vol. 9 | iss. 10 | e15677 | p. 1 http://www.researchprotocols.org/2020/10/e15677/ (page number not for citation purposes) Trumbull et al JMIR RESEARCH PROTOCOLS XSL • FO RenderX